Cambrian

@misc{walcott1891the70,
    author = "Walcott, C. D",
    title = "The North American Continent During Cambrian Time, in Twelfth Annual Report, United States Geological Survey",
    year = "1891",
    howpublished = "Washington, D.C., United States Geological Survey, p. 523-568",
    note = "talkorigins\_source = {true}; raw\_reference = {Walcott, C. D., 1891, The North American Continent During Cambrian Time, in Twelfth Annual Report, United States Geological Survey: Washington, D.C., United States Geological Survey, p. 523-568.}"
}

@misc{walcott1910abrupt71,
    author = "Walcott, C. D",
    title = "Abrupt appearance of the Cambrian fauna on the North American continent",
    year = "1910",
    howpublished = "Cambrian Geology and Paleontology, II: Smithsonian Miscellaneous Collections, v. 57, p. 1-16",
    note = "talkorigins\_source = {true}; raw\_reference = {Walcott, C. D., 1910, Abrupt appearance of the Cambrian fauna on the North American continent: Cambrian Geology and Paleontology, II: Smithsonian Miscellaneous Collections, v. 57, p. 1-16.}"
}

@misc{walcott1911middle72,
    author = "Walcott, C. D",
    title = "Middle Cambrian Merostomata. Cambrian Geology and Paleontology, II",
    year = "1911",
    howpublished = "Smithsonian Miscellaneous Collections, v. 57, p. 17-40",
    note = "talkorigins\_source = {true}; raw\_reference = {Walcott, C. D., 1911, Middle Cambrian Merostomata. Cambrian Geology and Paleontology, II: Smithsonian Miscellaneous Collections, v. 57, p. 17-40.}"
}

@misc{walcott1911middle73,
    author = "Walcott, C. D",
    title = "Middle Cambrian holothurians and medusae. Cambrian Geology and Paleontology",
    year = "1911",
    howpublished = "Smithsonian Miscellaneous Collections, v. 57, p. 41-68",
    note = "talkorigins\_source = {true}; raw\_reference = {Walcott, C. D., 1911, Middle Cambrian holothurians and medusae. Cambrian Geology and Paleontology: Smithsonian Miscellaneous Collections, v. 57, p. 41-68.}"
}

@misc{walcott1911middle74,
    author = "Walcott, C. D",
    title = "Middle Cambrian annelids. Cambrian Geology and Paleontology",
    year = "1911",
    howpublished = "Smithsonian Miscellaneous Collections, v. 57, p. 109-144",
    note = "talkorigins\_source = {true}; raw\_reference = {Walcott, C. D., 1911, Middle Cambrian annelids. Cambrian Geology and Paleontology: Smithsonian Miscellaneous Collections, v. 57, p. 109-144.}"
}

@misc{walcott1912middle75,
    author = "Walcott, C. D",
    title = "Middle Cambrian Branchiopoda, Malacostraca, Trilobita and Merostomata. Cambrian Geology and Paleontology, II",
    year = "1912",
    howpublished = "Smithsonian Miscellaneous Collections, v. 57, p. 145-228",
    note = "talkorigins\_source = {true}; raw\_reference = {Walcott, C. D., 1912, Middle Cambrian Branchiopoda, Malacostraca, Trilobita and Merostomata. Cambrian Geology and Paleontology, II: Smithsonian Miscellaneous Collections, v. 57, p. 145-228.}"
}

@misc{walcott1916evidence76,
    author = "Walcott, C. D",
    title = "Evidence of primitive life",
    year = "1916",
    howpublished = "Annual Report of the Smithsonian Institution for 1915 [published in 1916], p. 235-255",
    note = "talkorigins\_source = {true}; raw\_reference = {Walcott, C. D., 1916, Evidence of primitive life: Annual Report of the Smithsonian Institution for 1915 [published in 1916], p. 235-255.}"
}

@misc{walcott1918appendages77,
    author = "Walcott, C. D",
    title = "Appendages of trilobites. Cambrian Geology and Paleontology, IV",
    year = "1918",
    howpublished = "Smithsonian Miscellaneous Collections, v. 67, p. 115-216",
    note = "talkorigins\_source = {true}; raw\_reference = {Walcott, C. D., 1918, Appendages of trilobites. Cambrian Geology and Paleontology, IV: Smithsonian Miscellaneous Collections, v. 67, p. 115-216.}"
}

@misc{walcott1919middle78,
    author = "Walcott, C. D",
    title = "Middle Cambrian Algae. Cambrian Geology and Paleontology, IV",
    year = "1919",
    howpublished = "Smithsonian Miscellaneous Collections, v. 67, p. 217-260",
    note = "talkorigins\_source = {true}; raw\_reference = {Walcott, C. D., 1919, Middle Cambrian Algae. Cambrian Geology and Paleontology, IV: Smithsonian Miscellaneous Collections, v. 67, p. 217-260.}"
}

@misc{walcott1920middle79,
    author = "Walcott, C. D",
    title = "Middle Cambrian Spongiae. Cambrian Geology and Paleontology, IV",
    year = "1920",
    howpublished = "Smithsonian Miscellaneous Collections, v. 67, p. 261-364",
    note = "talkorigins\_source = {true}; raw\_reference = {Walcott, C. D., 1920, Middle Cambrian Spongiae. Cambrian Geology and Paleontology, IV: Smithsonian Miscellaneous Collections, v. 67, p. 261-364.}"
}

@inproceedings{hutchinson1931restudy49,
    author = "Hutchinson, G. E",
    title = "Restudy of some Burgess Shale fossils",
    year = "1931",
    booktitle = "Proceedings of the United States National Museum, v. 78, no. 11, p. 1-24",
    note = "talkorigins\_source = {true}; raw\_reference = {Hutchinson, G. E., 1931, Restudy of some Burgess Shale fossils: Proceedings of the United States National Museum, v. 78, no. 11, p. 1-24.}"
}

@misc{walcott1931addenda80,
    author = "Walcott, C. D",
    title = "Addenda to description of Burgess Shale fossils [with explanatory notes by C.E. Resser]",
    year = "1931",
    howpublished = "Smithsonian Miscellaneous Collections, v. 85, p. 1- 46",
    note = "talkorigins\_source = {true}; raw\_reference = {Walcott, C. D., 1931, Addenda to description of Burgess Shale fossils [with explanatory notes by C.E. Resser]: Smithsonian Miscellaneous Collections, v. 85, p. 1- 46.}"
}

@misc{mckee1945cambrian56,
    author = "McKee, E. D",
    title = "Cambrian History of the Grand Canyon Region",
    year = "1945",
    howpublished = "Washington, D.C., Carnegie Institute of Washington, 232 p.; Publication 563, Part I",
    note = "talkorigins\_source = {true}; raw\_reference = {McKee, E. D., 1945, Cambrian History of the Grand Canyon Region: Washington, D.C., Carnegie Institute of Washington, 232 p.; Publication 563, Part I.}"
}

@article{grant1962trilobite43,
    author = "Grant, R. E",
    title = "Trilobite distribution, upper Franconia Formation (Upper Cambrian), southeastern Minnesota",
    year = "1962",
    journal = "Journal of Paleontology, v. 36, p. 965- 998",
    note = "talkorigins\_source = {true}; raw\_reference = {Grant, R. E., 1962, Trilobite distribution, upper Franconia Formation (Upper Cambrian), southeastern Minnesota: Journal of Paleontology, v. 36, p. 965- 998.}"
}

@misc{semikhatov1962riphean63,
    author = "Semikhatov, M. A",
    title = "Riphean and Lower Cambrian of the Yenesei Ridge [in Russian]",
    year = "1962",
    howpublished = "Akad. Nauk SSSR, Geol. Inst., Trudy, 242 p",
    note = "talkorigins\_source = {true}; raw\_reference = {Semikhatov, M. A., 1962, Riphean and Lower Cambrian of the Yenesei Ridge [in Russian]: Akad. Nauk SSSR, Geol. Inst., Trudy, 242 p.}"
}

@techreport{weaver1962challenge81,
    author = "Weaver, P",
    title = "Challenge to Cambrian prospecting",
    year = "1962",
    howpublished = "Bulletin of the American Association of Petroleum Geologists, v. 46, no. 10, p. 1941-1943",
    note = "talkorigins\_source = {true}; raw\_reference = {Weaver, P., 1962, Challenge to Cambrian prospecting: Bulletin of the American Association of Petroleum Geologists, v. 46, no. 10, p. 1941-1943.}"
}

@misc{zharkov1963cambrian97,
    author = "Zharkov, M. A. and Chechel', E. I. and Knyasev, I. M",
    title = "Cambrian deposits of middle and upper stream of the river Kirenga",
    year = "1963",
    howpublished = "Academy of Sciences of the USSR Reports, v. 149, no. 4, p. 922-924; English translation by American Geological Institute, 1965, Academy of Science, USSR Reports, v.149, p. 65-66",
    note = "talkorigins\_source = {true}; raw\_reference = {Zharkov, M. A., Chechel', E. I., and Knyasev, I. M., 1963, Cambrian deposits of middle and upper stream of the river Kirenga: Academy of Sciences of the USSR Reports, v. 149, no. 4, p. 922-924; English translation by American Geological Institute, 1965, Academy of Science, USSR Reports, v.149, p. 65-66.}"
}

@misc{postnikov1964about60,
    author = "Postnikov, V. G. and Postnikova, I. Y",
    title = "About the possibilities of reef formations in lower Cambrian deposits in Markovskaya reconnaissance area (Irkutskii region)",
    year = "1964",
    howpublished = "Academy of Sciences of the USSR Reports, v. 158, no. 3, p. 605-608; English translation by American Geological Institute, 1965, Academy of Science, USSR Reports, v.158, p. 57-59",
    note = "talkorigins\_source = {true}; raw\_reference = {Postnikov, V. G., and Postnikova, I. Y., 1964, About the possibilities of reef formations in lower Cambrian deposits in Markovskaya reconnaissance area (Irkutskii region): Academy of Sciences of the USSR Reports, v. 158, no. 3, p. 605-608; English translation by American Geological Institute, 1965, Academy of Science, USSR Reports, v.158, p. 57-59.}"
}

@misc{silumov1964about64,
    author = "Silumov, I. N",
    title = "About correlative to Usol'skaya formation and facial structural zones of lower Cambrian foothills of East Sayan",
    year = "1964",
    howpublished = "Academy of Sciences of the USSR Reports, v. 156, no. 4, p. 838-840; English translation by American Geological Institute, 1965, Academy of Science, USSR Reports, v.156, p. 73-75",
    note = "talkorigins\_source = {true}; raw\_reference = {Silumov, I. N., 1964, About correlative to Usol'skaya formation and facial structural zones of lower Cambrian foothills of East Sayan: Academy of Sciences of the USSR Reports, v. 156, no. 4, p. 838-840; English translation by American Geological Institute, 1965, Academy of Science, USSR Reports, v.156, p. 73-75.}"
}

@misc{karpyshev1965about51,
    author = "Karpyshev, V. S",
    title = "About the relation between halogenous-carbonate and red- colored Cambrian formations in the western part of the Irkutskii cirque [ampitheatre]",
    year = "1965",
    howpublished = "Academy of Sciences of the USSR Reports, v. 160, no. 2, p. 425-448",
    note = "talkorigins\_source = {true}; raw\_reference = {Karpyshev, V. S., 1965, About the relation between halogenous-carbonate and red- colored Cambrian formations in the western part of the Irkutskii cirque [ampitheatre]: Academy of Sciences of the USSR Reports, v. 160, no. 2, p. 425-448.}"
}

@misc{analolyeva1966about2,
    author = "Analol'yeva, A. I. and Kharkov, M. A. and Sovetov, Y. K",
    title = "About correlation of the redcolored layers of the Vendian and the lowest part of the lower Cambrian of the Southwestern part of the Siberian Paltform",
    year = "1966",
    howpublished = "Academy of Sciences of the USSR Reports, v. 166, p. 413-416; English translation by American Geological Institute, 1966, Academy of Sciences USSR Reports, v.166, p. 24-26",
    note = "talkorigins\_source = {true}; raw\_reference = {Analol'yeva, A. I., Kharkov, M. A., and Sovetov, Y. K., 1966, About correlation of the redcolored layers of the Vendian and the lowest part of the lower Cambrian of the Southwestern part of the Siberian Paltform: Academy of Sciences of the USSR Reports, v. 166, p. 413-416; English translation by American Geological Institute, 1966, Academy of Sciences USSR Reports, v.166, p. 24-26.}"
}

@article{drobot1966new37,
    author = "Drobot, D. I. and Isayev, V. P",
    title = "New data about the composition and properties of the lower Cambrian oil of the Prilenskii region of the Irkutskii oil basin",
    year = "1966",
    journal = "Academy of Science of the USSR, Siberian Department, Geology and Geophysics, v. 10, p. 32-41; English translation by American Geological Institute, 1967, International Geological Review, v.9, No.8, p. 1028-1035",
    note = "talkorigins\_source = {true}; raw\_reference = {Drobot, D. I., and Isayev, V. P., 1966, New data about the composition and properties of the lower Cambrian oil of the Prilenskii region of the Irkutskii oil basin: Academy of Science of the USSR, Siberian Department, Geology and Geophysics, v. 10, p. 32-41; English translation by American Geological Institute, 1967, International Geological Review, v.9, No.8, p. 1028-1035.}"
}

@misc{lokhmatov1966change55,
    author = "Lokhmatov, G. I",
    title = "Change of contents of lower Cambrian carbonate deposits under the influence of consediment formation of geological structures (south of Siberian Platform)",
    year = "1966",
    howpublished = "Academy of Sciences of the USSR Reports, v. 170, no. 3, p. 661-664; English translation by American Geological Institute, 1967, Academy of Science, USSR Doklady, v.170, p.88-90",
    note = "talkorigins\_source = {true}; raw\_reference = {Lokhmatov, G. I., 1966, Change of contents of lower Cambrian carbonate deposits under the influence of consediment formation of geological structures (south of Siberian Platform): Academy of Sciences of the USSR Reports, v. 170, no. 3, p. 661-664; English translation by American Geological Institute, 1967, Academy of Science, USSR Doklady, v.170, p.88-90.}"
}

@misc{cowie1967life35,
    author = "Cowie, J. W",
    title = "Life in Pre-Cambrian and Early Cambrian times, in The Fossil Record",
    year = "1967",
    howpublished = "London, Geological Society of London, p. 17-35",
    note = "talkorigins\_source = {true}; raw\_reference = {Cowie, J. W., 1967, Life in Pre-Cambrian and Early Cambrian times, in The Fossil Record: London, Geological Society of London, p. 17-35.}"
}

@misc{kolosov1968complex53,
    author = "Kolosov, A. S. and Pustyl'nikov, A. M. and Kharkova, T. M",
    title = "Complex ferrum and manganese chlorides in Cambrian salt deposits of Kansko-Tassyevskoi basin",
    year = "1968",
    howpublished = "Academy of Sciences of the USSR Reports, v. 181, no. 6, p. 213-216",
    note = "talkorigins\_source = {true}; raw\_reference = {Kolosov, A. S., Pustyl'nikov, A. M., and Kharkova, T. M., 1968, Complex ferrum and manganese chlorides in Cambrian salt deposits of Kansko-Tassyevskoi basin: Academy of Sciences of the USSR Reports, v. 181, no. 6, p. 213-216.}"
}

@misc{pannella1968paleontological59,
    author = "Pannella, G. and MacClintock, C. and Thompson, M. N",
    title = "Paleontological evidence of variations in the length of synodic month since late Cambrian",
    year = "1968",
    howpublished = "Science, v. 162, p. 792-796",
    note = "talkorigins\_source = {true}; raw\_reference = {Pannella, G., MacClintock, C., and Thompson, M. N., 1968, Paleontological evidence of variations in the length of synodic month since late Cambrian: Science, v. 162, p. 792-796.}"
}

@misc{zharkov1969about96,
    author = "Zharkov, M. A",
    title = "About the amounts of salt deposits in the Cambrian era",
    year = "1969",
    howpublished = "Academy of Sciences of the USSR Reports, v. 184, no. 4, p. 913-914; English translation by American Geological Institute, 1969,Academy of Science, USSR Reports, v.184, p. 72-74",
    note = "talkorigins\_source = {true}; raw\_reference = {Zharkov, M. A., 1969, About the amounts of salt deposits in the Cambrian era: Academy of Sciences of the USSR Reports, v. 184, no. 4, p. 913-914; English translation by American Geological Institute, 1969,Academy of Science, USSR Reports, v.184, p. 72-74.}"
}

@misc{simonetta1970studies65,
    author = "Simonetta, A. M",
    title = "Studies of non-trilobite arthropods of the Burgess Shale (Middle Cambrian)",
    year = "1970",
    howpublished = "Palaeontographica Italica, v. 66 (n.s. 36), p. 35-45",
    note = "talkorigins\_source = {true}; raw\_reference = {Simonetta, A. M., 1970, Studies of non-trilobite arthropods of the Burgess Shale (Middle Cambrian): Palaeontographica Italica, v. 66 (n.s. 36), p. 35-45.}"
}

@article{vassoyevich1970more69,
    author = "Vassoyevich, N. B. et al",
    title = "More about the question of oil and gas prospects in late Cambrian deposits",
    year = "1970",
    journal = "Soviet Geology, v. 4, p. 66-79; English translation by American Geological Institute, 1971, International Geology Review, v.13, No.3, p. 407-418",
    note = "talkorigins\_source = {true}; raw\_reference = {Vassoyevich, N. B. et al., 1970, More about the question of oil and gas prospects in late Cambrian deposits: Soviet Geology, v. 4, p. 66-79; English translation by American Geological Institute, 1971, International Geology Review, v.13, No.3, p. 407-418.}"
}

@misc{karasev1971conditions50,
    author = "Karasev, O. I. et al",
    title = "Conditions for formation and accumulation of oil and gas in Vendian and Cambrian deposits of the southern part of the Siberian Platform",
    year = "1971",
    howpublished = "Irkutsk, East Siberian Publishing House, 206 p",
    note = "talkorigins\_source = {true}; raw\_reference = {Karasev, O. I. et al., 1971, Conditions for formation and accumulation of oil and gas in Vendian and Cambrian deposits of the southern part of the Siberian Platform: Irkutsk, East Siberian Publishing House, 206 p.}"
}

@techreport{whittington1971redescription82,
    author = "Whittington, H. B",
    title = "Redescription of Marrella splendens(Trilobitoidea) from the Burgess Shale, Middle Cambrian, British Columbia",
    year = "1971",
    howpublished = "Geological Survey of Canada Bulletin, v. 209, p. 1-24",
    note = "talkorigins\_source = {true}; raw\_reference = {Whittington, H. B., 1971, Redescription of Marrella splendens(Trilobitoidea) from the Burgess Shale, Middle Cambrian, British Columbia: Geological Survey of Canada Bulletin, v. 209, p. 1-24.}"
}

The Phyllopod Bed of the Burgess Shale, in which Walcott found the famous soft bodied fossils, consists of thin graded beds of calcareous siltstone and mud-stone, which are probably turbidites. The Burgess Shale was deposited on a reef front submarine fan, and the preservation of the fossils is probably due to rapid burial.

@article{doi101111j150239311972tb00850x,
    author = "Piper, David J. W.",
    title = "Sediments of the Middle Cambrian Burgess Shale, Canada",
    year = "1972",
    journal = "Lethaia",
    abstract = "The Phyllopod Bed of the Burgess Shale, in which Walcott found the famous soft bodied fossils, consists of thin graded beds of calcareous siltstone and mud-stone, which are probably turbidites. The Burgess Shale was deposited on a reef front submarine fan, and the preservation of the fossils is probably due to rapid burial.",
    url = "https://doi.org/10.1111/j.1502-3931.1972.tb00850.x",
    doi = "10.1111/j.1502-3931.1972.tb00850.x",
    openalex = "W2017481008"
}

@misc{khomentovsky1972key52,
    author = "Khomentovsky, V. V. and Shenfil', V. Y. and Yakshin, M. S. and Butakov, E. P",
    title = "Key Sections of the Upper Precambrian and Lower Cambrian Deposits of the Siberian Platform [in Russian]",
    year = "1972",
    howpublished = "Moscow, Nauka, 344 p",
    note = "talkorigins\_source = {true}; raw\_reference = {Khomentovsky, V. V., Shenfil', V. Y., Yakshin, M. S., and Butakov, E. P., 1972, Key Sections of the Upper Precambrian and Lower Cambrian Deposits of the Siberian Platform [in Russian]: Moscow, Nauka, 344 p.}"
}

@article{durham1974systematic38,
    author = "Durham, J. W",
    title = "Systematic position of Eldonia ludwigi Walcott",
    year = "1974",
    journal = "Journal of Paleontology, v. 48, p. 750-755",
    note = "talkorigins\_source = {true}; raw\_reference = {Durham, J. W., 1974, Systematic position of Eldonia ludwigi Walcott: Journal of Paleontology, v. 48, p. 750-755.}"
}

@techreport{whittington1974yohoia83,
    author = "Whittington, H. B",
    title = "Yohoia Walcott and Plenocaris n. gen., arthropods from the Burgess Shale, Middle Cambrian, British Columbia",
    year = "1974",
    howpublished = "Geological Survey of Canada Bulletin, v. 231, p. 1-21",
    note = "talkorigins\_source = {true}; raw\_reference = {Whittington, H. B., 1974, Yohoia Walcott and Plenocaris n. gen., arthropods from the Burgess Shale, Middle Cambrian, British Columbia: Geological Survey of Canada Bulletin, v. 231, p. 1-21.}"
}

Abstract Ten almost complete specimens have been studied in detail; nine coming from C. D. Walcott’s original collection, one from the recent re-investigation. The cuticle is preserved as a thin, dark layer; the external surface was apparently smooth, except for striations on the frontal process and adjacent to the mouth. Dorsally on the short cephalon were five eyes, thought to have been compound, the inner and outer pairs pedunculate, the median not stalked. From the anteroventral slope of the cephalon arose a long, flexible frontal process, divisible into a longer, cylindrical proximal portion, and a shorter, broad distal portion. The latter was divided longitudinally, each half bearing a group of long spines, directed inward and forward. The process probably contained a median, fluid-filled canal. The mouth was situated on the vertical, posteroventral wall of the cephalon, the alimentary canal U-shaped. The cylindrical axial region of the trunk tapered slightly backward, the alimentary canal situated ventrally and extending to the tip. The trunk was divided into a main portion of 15 segments, subequal in length, and a short posterior portion lacking segmentation. The junctions between segments gave a limited flexibility to the body. Each segment of the main portion of the trunk bore a pair of thin lateral lobes, directed downward and outward, overlapping, of maximum width medially, the lobes progressively more strongly prolonged backward. Dorsal to lobes 2-15, a paddle-shaped gill was attached near the base of the lobe. The ventral surface of the gill was flat, the outer, dorsal surface bearing imbricated, thin lamellae. The gills lay between adjacent, overlapping lateral lobes. Internally, in the main portion of the trunk what may have been diverticula of the gut are preserved, extending into the proximal portions of the lateral lobes. The posterior portion of the trunk bore three pairs of thin, lobate blades, directed upward and outward, overlapping in the opposite sense to the lateral lobes, the entire structure forming a tail fan. The dorsal margin of the tip of the axial region of the fan appears to have borne a pair of spines. The body is preserved with thin layers of rock between such parts as left and right eyes of a pair, adjacent lateral lobes, between gills and lobes, and between gill lamellae. The parts of the bodies are shown to have been entombed at varied angles to the horizontal bedding planes, and are greatly compressed. It is therefore considered that individuals were trapped in a cloud of sediment in suspension, moving along the sea bottom, and buried as it settled out. If so, the animal was benthonic in habit. Opabinia regalis may have ploughed shallowly in the bottom mud, propelled by movement of the lateral lobes. The eyes are presumed to have been capable of detecting movements in the surrounding waters, and the frontal process to have been used to explore the mud for food and bring it to the backward-facing mouth. The posterior region of the trunk may have aided in producing water currents over the dorsal surface of the body, or have aided in steering if the animal was capable of swimming. No structures that appear to have been antennae, and no other jointed appendages, have been observed, and the gills are not trilobite-like. O. regalis is not considered to have been a trilobitomorph arthiopod, nor is it regarded as an annelid. It may be descended from segmented animals from which arthropod phyla and/or annelids were derived.

@article{doi101098rstb19750033,
    author = "Whittington, H. B.",
    title = "The enigmatic animal Opabinia regalis, middle Cambrian, Burgess Shale, British Columbia",
    year = "1975",
    journal = "Philosophical transactions of the Royal Society of London. Series B, Biological sciences",
    abstract = "Abstract Ten almost complete specimens have been studied in detail; nine coming from C. D. Walcott’s original collection, one from the recent re-investigation. The cuticle is preserved as a thin, dark layer; the external surface was apparently smooth, except for striations on the frontal process and adjacent to the mouth. Dorsally on the short cephalon were five eyes, thought to have been compound, the inner and outer pairs pedunculate, the median not stalked. From the anteroventral slope of the cephalon arose a long, flexible frontal process, divisible into a longer, cylindrical proximal portion, and a shorter, broad distal portion. The latter was divided longitudinally, each half bearing a group of long spines, directed inward and forward. The process probably contained a median, fluid-filled canal. The mouth was situated on the vertical, posteroventral wall of the cephalon, the alimentary canal U-shaped. The cylindrical axial region of the trunk tapered slightly backward, the alimentary canal situated ventrally and extending to the tip. The trunk was divided into a main portion of 15 segments, subequal in length, and a short posterior portion lacking segmentation. The junctions between segments gave a limited flexibility to the body. Each segment of the main portion of the trunk bore a pair of thin lateral lobes, directed downward and outward, overlapping, of maximum width medially, the lobes progressively more strongly prolonged backward. Dorsal to lobes 2-15, a paddle-shaped gill was attached near the base of the lobe. The ventral surface of the gill was flat, the outer, dorsal surface bearing imbricated, thin lamellae. The gills lay between adjacent, overlapping lateral lobes. Internally, in the main portion of the trunk what may have been diverticula of the gut are preserved, extending into the proximal portions of the lateral lobes. The posterior portion of the trunk bore three pairs of thin, lobate blades, directed upward and outward, overlapping in the opposite sense to the lateral lobes, the entire structure forming a tail fan. The dorsal margin of the tip of the axial region of the fan appears to have borne a pair of spines. The body is preserved with thin layers of rock between such parts as left and right eyes of a pair, adjacent lateral lobes, between gills and lobes, and between gill lamellae. The parts of the bodies are shown to have been entombed at varied angles to the horizontal bedding planes, and are greatly compressed. It is therefore considered that individuals were trapped in a cloud of sediment in suspension, moving along the sea bottom, and buried as it settled out. If so, the animal was benthonic in habit. Opabinia regalis may have ploughed shallowly in the bottom mud, propelled by movement of the lateral lobes. The eyes are presumed to have been capable of detecting movements in the surrounding waters, and the frontal process to have been used to explore the mud for food and bring it to the backward-facing mouth. The posterior region of the trunk may have aided in producing water currents over the dorsal surface of the body, or have aided in steering if the animal was capable of swimming. No structures that appear to have been antennae, and no other jointed appendages, have been observed, and the gills are not trilobite-like. O. regalis is not considered to have been a trilobitomorph arthiopod, nor is it regarded as an annelid. It may be descended from segmented animals from which arthropod phyla and/or annelids were derived.",
    url = "https://doi.org/10.1098/rstb.1975.0033",
    doi = "10.1098/rstb.1975.0033",
    openalex = "W2128790411",
    references = "doi101098rstb19360008, doi101111j1469185x1958tb01258x, doi101111j150239311972tb00850x, doi1017161dtv0i05603, doi10182618200049639197506, doi10182618200049639197528, doi105281zenodo16286836, openalexw626977301"
}

New and old material of Olenoides serratus is described. Hypostome was fused with rostral plate, presence of metastome uncertain. Uniramous, multijointed antenna and posterior cercus were each of length three-quarters that of exoskeleton. Individuals of different sizes show 14-16 pairs of biramous appendages. Coxa was large, strongly spinose on ventral and adaxial margins. Inner, leg branch of 6 segments and terminal spines, long spines on proximal podomeres on ventral side. Outer branch arose from dorso-posterior margin of coxa, bilobed, inner lobe bearing some 50 slim filaments which extended back over two following appendages. All speeimens show appendages displaced, reconstruction suggests only 3 biramous pairs on cephalon, 7 on thorax, and 4 to 6 on pygidium. Speeies considered a predator and scavenger, food grasped by spinose leg branches, squeezed by gnathobases and passed forward in midline. Outer branches considered a gill, probably also used in swimming. Gait, trackway, and manner of digging and raking are suggested. No new material of Kootenia burgessensis found, Walcott's single specimen shows no clear evidence of anterior rim of shaft of gill branch.

@incollection{doi10182618200049639197506,
    author = "Whittington, H. B.",
    title = "Trilobites with appendages from the Middle Cambrian, Burgess Shale, British Columbia",
    year = "1975",
    booktitle = "Fossils and strata",
    abstract = "New and old material of Olenoides serratus is described. Hypostome was fused with rostral plate, presence of metastome uncertain. Uniramous, multijointed antenna and posterior cercus were each of length three-quarters that of exoskeleton. Individuals of different sizes show 14-16 pairs of biramous appendages. Coxa was large, strongly spinose on ventral and adaxial margins. Inner, leg branch of 6 segments and terminal spines, long spines on proximal podomeres on ventral side. Outer branch arose from dorso-posterior margin of coxa, bilobed, inner lobe bearing some 50 slim filaments which extended back over two following appendages. All speeimens show appendages displaced, reconstruction suggests only 3 biramous pairs on cephalon, 7 on thorax, and 4 to 6 on pygidium. Speeies considered a predator and scavenger, food grasped by spinose leg branches, squeezed by gnathobases and passed forward in midline. Outer branches considered a gill, probably also used in swimming. Gait, trackway, and manner of digging and raking are suggested. No new material of Kootenia burgessensis found, Walcott's single specimen shows no clear evidence of anterior rim of shaft of gill branch.",
    url = "https://doi.org/10.18261/8200049639-1975-06",
    doi = "10.18261/8200049639-1975-06",
    openalex = "W4385617811",
    references = "doi101002gj3350070104, doi101016003101827190040x, doi101098rstb19640001, doi101111j109636421952tb01854x, doi101111j109636421954tb02211x, doi101111j109636421973tb00790x, doi101111j150239311969tb01259x, doi10182618200093301197301, openalexw2413383410, openalexw2604533467"
}

Previously studied specimens and additional material of Burgessia bella from old and new collections have been prepared, and new photographs accompanied by explanatory line drawings are given together with reconstructions in various aspects. The carapace is roughly circular, invaginated posteriorly, and extends back above the trunk leaving only the long unsegmented posterior spine uncovered. The carapace is gently convex sagitally and transversely. No cephalic doublure or ventral plates are present. The body is segmented and appears to have been subcircular in cross-section, with no pleurae. The mouth is ventral. Four appendagebearing somites lie within the cephalon and the remaining eight in the trunk. A large kidney-shaped gut-caecal system occupies the lateral portion of the carapace, being connected by a wide diverticulum to the alimentary canal at the posterior cephalic somite. The so-called eyes are reinterpreted as attachment areas for muscles connecting the anterior end of the body to the carapace. The anterior cephalic appendages consist of a pair of multijointed uniramous antenna, the second, third and fourth are biramous, consisting of a jointed walking-leg and a whip-like flagellum. All the trunk appendages, "except the last, are biramous and consist of a coxa with telopod composed of six segments and terminal cIaws, and a small lateral, leaf-like gill branch presumed to be attached to the coxa. The posterior appendage is believed uniramous consisting simply of a backwardly curved spike. The telson consists of an anal segment lacking lateral appendages, and a long, tapering unsegmented caudal spine jointed at the base to the anal segment. Dark stains are occasionally associated with specimens and are presumed to represent organic matter squeezed out of the body during compaction. The carapace ranges from four to seventeen mm in maximum width, the size-frequency histogram being unimodal except that the smallest three specimens are somewhat detached. The occurrence within the Phyllopod bed cIosely matches that of Waptia, Marrella, and Yohoia.

@incollection{doi10182618200049639197528,
    author = "Hughes, Christopher P.",
    title = "Redescription of Burgessia bella from the Middle Cambrian Burgess Shale, British Columbia",
    year = "1975",
    booktitle = "Fossils and strata",
    abstract = {Previously studied specimens and additional material of Burgessia bella from old and new collections have been prepared, and new photographs accompanied by explanatory line drawings are given together with reconstructions in various aspects. The carapace is roughly circular, invaginated posteriorly, and extends back above the trunk leaving only the long unsegmented posterior spine uncovered. The carapace is gently convex sagitally and transversely. No cephalic doublure or ventral plates are present. The body is segmented and appears to have been subcircular in cross-section, with no pleurae. The mouth is ventral. Four appendagebearing somites lie within the cephalon and the remaining eight in the trunk. A large kidney-shaped gut-caecal system occupies the lateral portion of the carapace, being connected by a wide diverticulum to the alimentary canal at the posterior cephalic somite. The so-called eyes are reinterpreted as attachment areas for muscles connecting the anterior end of the body to the carapace. The anterior cephalic appendages consist of a pair of multijointed uniramous antenna, the second, third and fourth are biramous, consisting of a jointed walking-leg and a whip-like flagellum. All the trunk appendages, "except the last, are biramous and consist of a coxa with telopod composed of six segments and terminal cIaws, and a small lateral, leaf-like gill branch presumed to be attached to the coxa. The posterior appendage is believed uniramous consisting simply of a backwardly curved spike. The telson consists of an anal segment lacking lateral appendages, and a long, tapering unsegmented caudal spine jointed at the base to the anal segment. Dark stains are occasionally associated with specimens and are presumed to represent organic matter squeezed out of the body during compaction. The carapace ranges from four to seventeen mm in maximum width, the size-frequency histogram being unimodal except that the smallest three specimens are somewhat detached. The occurrence within the Phyllopod bed cIosely matches that of Waptia, Marrella, and Yohoia.},
    url = "https://doi.org/10.18261/8200049639-1975-28",
    doi = "10.18261/8200049639-1975-28",
    openalex = "W4385628773"
}

@misc{hughes1975redescription48,
    author = "Hughes, C. P",
    title = "Redescription of Burgessia bella from the Middle Cambrian Burgess Shale, British Columbia",
    year = "1975",
    howpublished = "Fossils and Strata (Oslo), v. 4, p. 415-435",
    note = "talkorigins\_source = {true}; raw\_reference = {Hughes, C. P., 1975, Redescription of Burgessia bella from the Middle Cambrian Burgess Shale, British Columbia: Fossils and Strata (Oslo), v. 4, p. 415-435.}"
}

@misc{levchenko1975prospects54,
    author = "Levchenko, I. G",
    title = "Prospects of oil and gas in Cambrian deposits of Tungusskaya syneclise and its belt",
    year = "1975",
    howpublished = "Geology of Oil and Gas, v. 1, p. 1-9",
    note = "talkorigins\_source = {true}; raw\_reference = {Levchenko, I. G., 1975, Prospects of oil and gas in Cambrian deposits of Tungusskaya syneclise and its belt: Geology of Oil and Gas, v. 1, p. 1-9.}"
}

@article{whittington1975the84,
    author = "Whittington, H. B",
    title = "The enigmatic animal Opabinia regalis, Middle Cambrian, Burgess Shale, British Columbia",
    year = "1975",
    journal = "Philosophical Transactions of the Royal Society, London B, v. 271, p. 1-43",
    note = "talkorigins\_source = {true}; raw\_reference = {Whittington, H. B., 1975, The enigmatic animal Opabinia regalis, Middle Cambrian, Burgess Shale, British Columbia: Philosophical Transactions of the Royal Society, London B, v. 271, p. 1-43.}"
}

@misc{whittington1975trilobites85,
    author = "Whittington, H. B",
    title = "Trilobites with appendages from the Middle Cambrian, Burgess Shale, British Columbia",
    year = "1975",
    howpublished = "Fossils and Strata (Oslo), v. 4, p. 97-136",
    note = "talkorigins\_source = {true}; raw\_reference = {Whittington, H. B., 1975, Trilobites with appendages from the Middle Cambrian, Burgess Shale, British Columbia: Fossils and Strata (Oslo), v. 4, p. 97-136.}"
}

@techreport{briggs1976the6,
    author = "Briggs, D. E. G",
    title = "The arthropod Branchiocaris n. gen., Middle Cambrian, Burgess Shale, British Columbia",
    year = "1976",
    howpublished = "Geological Survey of Canada Bulletin, v. 264, p. 1-29",
    note = "talkorigins\_source = {true}; raw\_reference = {Briggs, D. E. G., 1976, The arthropod Branchiocaris n. gen., Middle Cambrian, Burgess Shale, British Columbia: Geological Survey of Canada Bulletin, v. 264, p. 1-29.}"
}

@misc{conwaymorris1976a21,
    author = "Conway Morris, S",
    title = "A new Cambrian lophophorate from the Burgess Shale of British Columbia",
    year = "1976",
    howpublished = "Palaeontology, v. 19, p. 199-222",
    note = "talkorigins\_source = {true}; raw\_reference = {Conway Morris, S., 1976, A new Cambrian lophophorate from the Burgess Shale of British Columbia: Palaeontology, v. 19, p. 199-222.}"
}

@misc{conwaymorris1976nectocaris20,
    author = "Conway Morris, S",
    title = "Nectocaris pteryx, a new organism from the Middle Cambrian Burgess Shale of British Columbia",
    year = "1976",
    howpublished = "Nueus Jahrbuch fr Geologie und Palontologie, v. 12, p. 705-713",
    note = "talkorigins\_source = {true}; raw\_reference = {Conway Morris, S., 1976, Nectocaris pteryx, a new organism from the Middle Cambrian Burgess Shale of British Columbia: Nueus Jahrbuch fr Geologie und Palontologie, v. 12, p. 705-713.}"
}

Twenty-eight species of fifteen genera of Middle Cambrian molluscs are described from tiny phosphatic moulds or silica replicas of the shells. The molluscs were etched from limestones at two sites: one in the earliest Middle Cambrian Coonigan Formation of the Mootwingee area, 130 km northeast of Broken Hill, New South Wales; and another in the middle Middle Cambrian Currant Bush Limestone of the Thorntonia area, 150 km northwest of Mt Isa, Queensland. These unusually diverse collections show that many different kinds of molluscs lived in the tropical Australian seas of the Middle Cambrian and provide new information on the way the molluscan classes Cephalopoda, Gastropoda, Rostro- conchia, and Pelecypoda evolved. In other sections, we discuss the problems of classifying and naming Cambrian molluscs; define a number of terms that can be used to describe shell form (including a new adjective, gyrogastric); reclassify the Class Monoplacophora after incorporating the helcionellacean and bellerophontacean “gastropods”; and outline the early record and history of the Mollusca. New taxa are: the Families Scenellidae (nom. transl. ex Scenellinae Wenz 1938) and Yochelcionellidae; the genera Eotebenna (Yochelcionellidae), Mellopegma (Procarinariidae), and ProtoweneHa (Multifariidae); and the species Helcionella terraustralis, Latouchella accordionata, L. merino, L. penecyrano, Yochelcionella daleki, Y. ostentata, Eotebenna pontifex, E. papilio, Mellopegma georginensis, Stenotheca tepee, S. pojetai, Protowenella flemingi, Pelagiella deltoides, P. corinthiana, and Myonai? queenslandica.

@article{doi10108003115517608619064,
    author = "Runnegar, Bruce and Jell, Peter A.",
    title = "Australian Middle Cambrian molluscs and their bearing on early molluscan evolution",
    year = "1976",
    journal = "Alcheringa An Australasian Journal of Palaeontology",
    abstract = "Twenty-eight species of fifteen genera of Middle Cambrian molluscs are described from tiny phosphatic moulds or silica replicas of the shells. The molluscs were etched from limestones at two sites: one in the earliest Middle Cambrian Coonigan Formation of the Mootwingee area, 130 km northeast of Broken Hill, New South Wales; and another in the middle Middle Cambrian Currant Bush Limestone of the Thorntonia area, 150 km northwest of Mt Isa, Queensland. These unusually diverse collections show that many different kinds of molluscs lived in the tropical Australian seas of the Middle Cambrian and provide new information on the way the molluscan classes Cephalopoda, Gastropoda, Rostro- conchia, and Pelecypoda evolved. In other sections, we discuss the problems of classifying and naming Cambrian molluscs; define a number of terms that can be used to describe shell form (including a new adjective, gyrogastric); reclassify the Class Monoplacophora after incorporating the helcionellacean and bellerophontacean “gastropods”; and outline the early record and history of the Mollusca. New taxa are: the Families Scenellidae (nom. transl. ex Scenellinae Wenz 1938) and Yochelcionellidae; the genera Eotebenna (Yochelcionellidae), Mellopegma (Procarinariidae), and ProtoweneHa (Multifariidae); and the species Helcionella terraustralis, Latouchella accordionata, L. merino, L. penecyrano, Yochelcionella daleki, Y. ostentata, Eotebenna pontifex, E. papilio, Mellopegma georginensis, Stenotheca tepee, S. pojetai, Protowenella flemingi, Pelagiella deltoides, P. corinthiana, and Myonai? queenslandica.",
    url = "https://doi.org/10.1080/03115517608619064",
    doi = "10.1080/03115517608619064",
    openalex = "W2124323345",
    references = "doi101130spe32, doi102475ajs2748833"
}

@misc{bengtson1977early4,
    author = "Bengtson, S",
    title = "Early Cambrian button-shaped phosphatic microfossils from the Siberian platform",
    year = "1977",
    howpublished = "Palaeontology, v. 20, p. 751-762",
    note = "talkorigins\_source = {true}; raw\_reference = {Bengtson, S., 1977, Early Cambrian button-shaped phosphatic microfossils from the Siberian platform: Palaeontology, v. 20, p. 751-762.}"
}

@misc{briggs1977bivalved7,
    author = "Briggs, D. E. G",
    title = "Bivalved arthropods from the Cambrian Burgess Shale of British Columbia",
    year = "1977",
    howpublished = "Palaeontology, v. 20, p. 595-621",
    note = "talkorigins\_source = {true}; raw\_reference = {Briggs, D. E. G., 1977, Bivalved arthropods from the Cambrian Burgess Shale of British Columbia: Palaeontology, v. 20, p. 595-621.}"
}

@misc{conwaymorris1977a22,
    author = "Conway Morris, S",
    title = "A new entoproct-like organism from the Burgess Shale of British Columbia",
    year = "1977",
    howpublished = "Palaeontology, v. 20, p. 833-845",
    note = "talkorigins\_source = {true}; raw\_reference = {Conway Morris, S., 1977, A new entoproct-like organism from the Burgess Shale of British Columbia: Palaeontology, v. 20, p. 833-845.}"
}

@misc{conwaymorris1977a23,
    author = "Conway Morris, S",
    title = "A redescription of the Middle Cambrian worm Amiskwia sagittiformis Walcott from the Burgess Shale of British Columbia",
    year = "1977",
    howpublished = "Palontologische Zeitschrift, v. 51, p. 271-287",
    note = "talkorigins\_source = {true}; raw\_reference = {Conway Morris, S., 1977, A redescription of the Middle Cambrian worm Amiskwia sagittiformis Walcott from the Burgess Shale of British Columbia: Palontologische Zeitschrift, v. 51, p. 271-287.}"
}

@misc{conwaymorris1977a24,
    author = "Conway Morris, S",
    title = "A new metazoan from the Cambrian Burgess Shale of British Columbia",
    year = "1977",
    howpublished = "Palaeontology, v. 20, p. 623-640",
    note = "talkorigins\_source = {true}; raw\_reference = {Conway Morris, S., 1977, A new metazoan from the Cambrian Burgess Shale of British Columbia: Palaeontology, v. 20, p. 623-640.}"
}

@misc{conwaymorris1977fossil25,
    author = "Conway Morris, S",
    title = "Fossil priapulid worms, 20 of Special Papers in Palaeontology",
    year = "1977",
    howpublished = "London, Palaeontological Association",
    note = "talkorigins\_source = {true}; raw\_reference = {Conway Morris, S., 1977, Fossil priapulid worms, 20 of Special Papers in Palaeontology: London, Palaeontological Association.}"
}

@article{whittington1977the86,
    author = "Whittington, H. B",
    title = "The Middle Cambrian trilobite Naraoia, Burgess Shale, British Columbia",
    year = "1977",
    journal = "Philosophical Transactions of the Royal Society, London B, v. 280, p. 409-443",
    note = "talkorigins\_source = {true}; raw\_reference = {Whittington, H. B., 1977, The Middle Cambrian trilobite Naraoia, Burgess Shale, British Columbia: Philosophical Transactions of the Royal Society, London B, v. 280, p. 409-443.}"
}

@article{briggs1978the8,
    author = "Briggs, D. E. G",
    title = "The morphology, mode of life, and affinities of Canadaspis perfecta (Crustacea",
    year = "1978",
    journal = "Phyllocarida), Middle Cambrian, Burgess Shale, British Columbia: Philosophical Transactions of the Royal Society, London B, v. 281, p. 439-487",
    note = "talkorigins\_source = {true}; raw\_reference = {Briggs, D. E. G., 1978, The morphology, mode of life, and affinities of Canadaspis perfecta (Crustacea: Phyllocarida), Middle Cambrian, Burgess Shale, British Columbia: Philosophical Transactions of the Royal Society, London B, v. 281, p. 439-487.}"
}

@article{conwaymorris1978laggania26,
    author = "Conway Morris, S",
    title = "Laggania cambria Walcott",
    year = "1978",
    journal = "A composite fossil: Journal of Paleontology, v. 52, p. 126-131",
    note = "talkorigins\_source = {true}; raw\_reference = {Conway Morris, S., 1978, Laggania cambria Walcott: A composite fossil: Journal of Paleontology, v. 52, p. 126-131.}"
}

Abstract A detailed description and reconstruction of Canadaspis perfecta demonstrates its status as the earliest well-preserved crustacean. The cephalon consisted of five somites (in addition to the eyes), the thorax eight, and the abdomen seven, excluding the telson. Two pairs of apparently uniramous antennae flanked a median cephalic spine. The mandible bore a massive incisor process posterior of a molar area made up of finer spines, and apparently lacked a palp. The first and second maxillae were essentially similar to the eight pairs of thoracopods, with a multisegmented inner ramus, and foliaceous outer ramus made up of wide filaments attached to a proximal lobe. A bivalved carapace covered the thorax; no rostral plate was present. The abdomen lacked appendages, apart from a pair of spinose ventral projections of the pre-telson somite. There was no caudal furca. The evidence suggests that C. perfecta fed on coarse particles, possibly with the aid of currents set up by the biramous appendages. The erection of a new order Canadaspidida and family Canadaspididae Novozhilov (in Orlov 1960) to include Canadaspis is vindicated, and they are re-defined and the subclass Phyllocarida amended to include them.

@article{doi101098rstb19780005,
    author = "Briggs, Derek E. G.",
    title = "The morphology, mode of life, and affinities of Canadaspis perfecta (Crustacea: Phyllocarida), Middle Cambrian, Burgess Shale, British Columbia",
    year = "1978",
    journal = "Philosophical transactions of the Royal Society of London. Series B, Biological sciences",
    abstract = "Abstract A detailed description and reconstruction of Canadaspis perfecta demonstrates its status as the earliest well-preserved crustacean. The cephalon consisted of five somites (in addition to the eyes), the thorax eight, and the abdomen seven, excluding the telson. Two pairs of apparently uniramous antennae flanked a median cephalic spine. The mandible bore a massive incisor process posterior of a molar area made up of finer spines, and apparently lacked a palp. The first and second maxillae were essentially similar to the eight pairs of thoracopods, with a multisegmented inner ramus, and foliaceous outer ramus made up of wide filaments attached to a proximal lobe. A bivalved carapace covered the thorax; no rostral plate was present. The abdomen lacked appendages, apart from a pair of spinose ventral projections of the pre-telson somite. There was no caudal furca. The evidence suggests that C. perfecta fed on coarse particles, possibly with the aid of currents set up by the biramous appendages. The erection of a new order Canadaspidida and family Canadaspididae Novozhilov (in Orlov 1960) to include Canadaspis is vindicated, and they are re-defined and the subclass Phyllocarida amended to include them.",
    url = "https://doi.org/10.1098/rstb.1978.0005",
    doi = "10.1098/rstb.1978.0005",
    openalex = "W2118011680",
    references = "doi10108000222937908562419, doi10108002693445189212028021, doi101086279772, doi101098rstb19750033, doi101111j109636421973tb00790x, doi101111j1469185x1958tb01258x, doi1023072411440, doi102307sysbio131453, doi105281zenodo16273729, doi105962bhltitle15764"
}

@article{whittington1978the87,
    author = "Whittington, H. B",
    title = "The lobopod animal Aysheaia pendunculata Walcott, Middle Cambrian, Burgess Shale, British Columbia",
    year = "1978",
    journal = "Philosophical Transactions of the Royal Society, London B, v. 284, p. 165-197",
    note = "talkorigins\_source = {true}; raw\_reference = {Whittington, H. B., 1978, The lobopod animal Aysheaia pendunculata Walcott, Middle Cambrian, Burgess Shale, British Columbia: Philosophical Transactions of the Royal Society, London B, v. 284, p. 165-197.}"
}

@misc{briggs1979anomalocaris9,
    author = "Briggs, D. E. G",
    title = "Anomalocaris, the largest known Cambrian arthropod",
    year = "1979",
    howpublished = "Palaeontology, v. 22, p. 631-634",
    note = "talkorigins\_source = {true}; raw\_reference = {Briggs, D. E. G., 1979, Anomalocaris, the largest known Cambrian arthropod: Palaeontology, v. 22, p. 631-634.}"
}

@article{conwaymorris1979middle27,
    author = "Conway Morris, S",
    title = "Middle Cambrian polychaetes from the Burgess Shale of British Columbia",
    year = "1979",
    journal = "Philosophical Transactions of the Royal Society, London B, v. 285, p. 227-274",
    note = "talkorigins\_source = {true}; raw\_reference = {Conway Morris, S., 1979, Middle Cambrian polychaetes from the Burgess Shale of British Columbia: Philosophical Transactions of the Royal Society, London B, v. 285, p. 227-274.}"
}

@misc{conwaymorris1979the33,
    author = "Conway Morris, S. and Whittington, H. B",
    title = "The animals of the Burgess Shale",
    year = "1979",
    howpublished = "Scientific American, v. 240 (January), no. 1, p. 122-133",
    note = "talkorigins\_source = {true}; raw\_reference = {Conway Morris, S., and Whittington, H. B., 1979, The animals of the Burgess Shale: Scientific American, v. 240 (January), no. 1, p. 122-133.}"
}

The preservation of soft parts in fossils is rare because fossilization usually occurs long after decay has destroyed soft tissues. A notable exception is the soft-bodied fauna from the Middle Cambrian Burgess Shale (about 530 million years old) located near Field in southern British Columbia, where both completely soft-bodied groups (e.g. polychaetes) and the soft parts of creatures with resistant skeletons (e.g. trilobites) are beautifully preserved. In addition, this fauna includes animals with fragile skeletons of thin cuticle that normally do not fossilize. The Burgess Shale fauna is of special impor­ tance because it permits a unique glimpse of the period shortly after the upper Precambrian-lowermost Cambrian radiation of the Metazoa (26). In 1909 Charles Doolittle Walcott (Secretary of the Smithsonian Institu­ tion), returning from a field season, stopped to split open a rock that blocked a trail on the western slopes between Wapta Mountain and Mount Field. The rock contained soft-bodied fossils. The following year Walcott and his two sons located the original stratum: the Burgess Shale. Quarrying contin­ ued for several seasons (1910--l3, 1917), and more than 40,000 specimens were shipped to the Smithsonian Institution (USNM). Subsequent expedi­ tions by Harvard University (MCZ) in 1930 (92, 94), the Geological Survey of Canada (GSC) in 1966 and 1967 (153), and the Royal Ontario Museum (Toronto) in 1975 collected more material. After Walcott's preliminary publications (l35-l37, l39-146, 148), a much needed reinvestigation was undertaken by the GSC, with H. B. Whittington directing the paleontologi­ cal work.

@article{doi101146annureves10110179001551,
    author = "Morris, Simon Conway",
    title = "The Burgess Shale (Middle Cambrian) Fauna",
    year = "1979",
    journal = "Annual Review of Ecology and Systematics",
    abstract = "The preservation of soft parts in fossils is rare because fossilization usually occurs long after decay has destroyed soft tissues. A notable exception is the soft-bodied fauna from the Middle Cambrian Burgess Shale (about 530 million years old) located near Field in southern British Columbia, where both completely soft-bodied groups (e.g. polychaetes) and the soft parts of creatures with resistant skeletons (e.g. trilobites) are beautifully preserved. In addition, this fauna includes animals with fragile skeletons of thin cuticle that normally do not fossilize. The Burgess Shale fauna is of special impor­ tance because it permits a unique glimpse of the period shortly after the upper Precambrian-lowermost Cambrian radiation of the Metazoa (26). In 1909 Charles Doolittle Walcott (Secretary of the Smithsonian Institu­ tion), returning from a field season, stopped to split open a rock that blocked a trail on the western slopes between Wapta Mountain and Mount Field. The rock contained soft-bodied fossils. The following year Walcott and his two sons located the original stratum: the Burgess Shale. Quarrying contin­ ued for several seasons (1910--l3, 1917), and more than 40,000 specimens were shipped to the Smithsonian Institution (USNM). Subsequent expedi­ tions by Harvard University (MCZ) in 1930 (92, 94), the Geological Survey of Canada (GSC) in 1966 and 1967 (153), and the Royal Ontario Museum (Toronto) in 1975 collected more material. After Walcott's preliminary publications (l35-l37, l39-146, 148), a much needed reinvestigation was undertaken by the GSC, with H. B. Whittington directing the paleontologi­ cal work.",
    url = "https://doi.org/10.1146/annurev.es.10.110179.001551",
    doi = "10.1146/annurev.es.10.110179.001551",
    openalex = "W2123112979",
    references = "doi101007bf02989565, doi101016b9780125886062500126, doi101016s0070457108711324, doi101017s0094837300005236, doi101098rstb19770117, doi101111j150239311975tb01311x, doi101130gsab49195, doi105479si009638017628061, openalexw2604533467, openalexw582491535"
}

@misc{ford1979precambrian40,
    author = "Ford, T. D",
    title = "Precambrian Fossils and the Origin of the Phyla, in House, R. M., ed., The Origin of the Major Invertebrate Groups",
    year = "1979",
    howpublished = "Systematics Association; Publication No. 12",
    note = "talkorigins\_source = {true}; raw\_reference = {Ford, T. D., 1979, Precambrian Fossils and the Origin of the Phyla, in House, R. M., ed., The Origin of the Major Invertebrate Groups: Systematics Association; Publication No. 12.}"
}

@inproceedings{ford1980the41,
    author = "Ford, T. D",
    title = "The Edicarian fossils of Charnwood Forest, Leicestershire",
    year = "1980",
    booktitle = "Proceedings of the Geologist's Association, v. 91, p. 81-83",
    note = "talkorigins\_source = {true}; raw\_reference = {Ford, T. D., 1980, The Edicarian fossils of Charnwood Forest, Leicestershire: Proceedings of the Geologist's Association, v. 91, p. 81-83.}"
}

@inproceedings{whittington1980the88,
    author = "Whittington, H. B",
    title = "The significance of the fauna of the Burgess Shale, Middle Cambrian, British Columbia",
    year = "1980",
    booktitle = "Proceedings of the Geologist's Association, v. 91, p. 127-148",
    note = "talkorigins\_source = {true}; raw\_reference = {Whittington, H. B., 1980, The significance of the fauna of the Burgess Shale, Middle Cambrian, British Columbia: Proceedings of the Geologist's Association, v. 91, p. 127-148.}"
}

@misc{briggs1981relationships11,
    author = "Briggs, D. E. G",
    title = "Relationships of arthropods from the Burgess Shale and other Cambrian sequences",
    year = "1981",
    howpublished = "Open File Report 81-743, United States Geological Survey, pp. 38-41",
    note = "talkorigins\_source = {true}; raw\_reference = {Briggs, D. E. G., 1981, Relationships of arthropods from the Burgess Shale and other Cambrian sequences. Open File Report 81-743, United States Geological Survey, pp. 38-41.}"
}

@article{briggs1981the10,
    author = "Briggs, D. E. G",
    title = "The arthropod Odaraia alata Walcott, Middle Cambrian, Burgess Shale, British Columbia",
    year = "1981",
    journal = "Philosophical Transactions of the Royal Society, London B, v. 291, p. 541-585",
    note = "talkorigins\_source = {true}; raw\_reference = {Briggs, D. E. G., 1981, The arthropod Odaraia alata Walcott, Middle Cambrian, Burgess Shale, British Columbia: Philosophical Transactions of the Royal Society, London B, v. 291, p. 541-585.}"
}

@article{bruton1981the15,
    author = "Bruton, D. L",
    title = "The arthropod Sidneyia inexpectans, Middle Cambrian, Burgess Shale, British Columbia",
    year = "1981",
    journal = "Philosophical Transactions of the Royal Society, London B, v. 295, p. 619-656",
    note = "talkorigins\_source = {true}; raw\_reference = {Bruton, D. L., 1981, The arthropod Sidneyia inexpectans, Middle Cambrian, Burgess Shale, British Columbia: Philosophical Transactions of the Royal Society, London B, v. 295, p. 619-656.}"
}

Abstract This, the first detailed description, interpretation and reconstruction of Odaraia alata, is based on all 29 known specimens. These include material of Eurysaces pielus Simonetta and Delle Cave, 1975, which is synonymized with O. alata herein. The head bore a pair of large eyes anteriorly and a paired mandible posteriorly. Features between these are poorly defined and the number of limb-bearing cephalic somites is unknown. The carapace was bivalved and essentially tubular in configuration, enclosing most of the body anteriorly. The trunk included up to at least 45 uniform short wide limb-bearing somites. The trunk appendages were biramous (with the possible exception of the first two), with an outer lamellate branch projecting dorsad of a segmented, spinose and apparently sometimes bifurcate inner branch which shows some evidence of variation along the trunk. The telson bore three large flukes, two projecting laterally and one vertically. The evidence suggests that O. alata fed by employing the carapace as a filter chamber within which the appendages, which trapped small pelagic animals, were confined. The arthropod probably swam on its back, using the appendages. Although the flukes did not articulate proximally, the telson appears to have been well adapted as a stabilizing and steering organ. O. alata shows some similarities to the Crustacea, particularly the Branchiopoda, but the preservation of the features of the cephalon is inadequate to allow its affinities to be determined unequivocally. It is classified in the family Odaraidae Simonetta and Delle Cave, 1975, but assignment to a higher taxon within the arthropods is not considered to be justified.

@article{doi101098rstb19810007,
    author = "Briggs, Derek E. G.",
    title = "The arthropod Odaraia alata Walcott, Middle Cambrian, Burgess Shale, British Columbia",
    year = "1981",
    journal = "Philosophical transactions of the Royal Society of London. Series B, Biological sciences",
    abstract = "Abstract This, the first detailed description, interpretation and reconstruction of Odaraia alata, is based on all 29 known specimens. These include material of Eurysaces pielus Simonetta and Delle Cave, 1975, which is synonymized with O. alata herein. The head bore a pair of large eyes anteriorly and a paired mandible posteriorly. Features between these are poorly defined and the number of limb-bearing cephalic somites is unknown. The carapace was bivalved and essentially tubular in configuration, enclosing most of the body anteriorly. The trunk included up to at least 45 uniform short wide limb-bearing somites. The trunk appendages were biramous (with the possible exception of the first two), with an outer lamellate branch projecting dorsad of a segmented, spinose and apparently sometimes bifurcate inner branch which shows some evidence of variation along the trunk. The telson bore three large flukes, two projecting laterally and one vertically. The evidence suggests that O. alata fed by employing the carapace as a filter chamber within which the appendages, which trapped small pelagic animals, were confined. The arthropod probably swam on its back, using the appendages. Although the flukes did not articulate proximally, the telson appears to have been well adapted as a stabilizing and steering organ. O. alata shows some similarities to the Crustacea, particularly the Branchiopoda, but the preservation of the features of the cephalon is inadequate to allow its affinities to be determined unequivocally. It is classified in the family Odaraidae Simonetta and Delle Cave, 1975, but assignment to a higher taxon within the arthropods is not considered to be justified.",
    url = "https://doi.org/10.1098/rstb.1981.0007",
    doi = "10.1098/rstb.1981.0007",
    openalex = "W2016692926",
    references = "doi101017s0022112070001830, doi10108003115517908565437, doi101098rstb19750033, doi101098rstb19780005, doi101098rstb19790006, doi10182618200049639197506, doi1023072412988, doi105281zenodo15992748, doi105281zenodo16490103, doi105962bhlpart4119"
}

Abstract Old and new specimens of Sidneyia inexpectans have been studied and are accompanied by explanatory drawings and photographs. New reconstructions of the animal are given together with a three-dimensional model. The body consisted of a cephalon with a long backwardly directed doublure, a thorax of nine articulating somites, abdomen with cylindrical exoskeleton of two or three somites and a telson. A caudal fan was formed by a pair of uropods articulating at the posterior margin of the last abdominal somite. The cephalon had stalked eyes and preoral antennae but no walking or grasping appendages. The first four somites of the thorax had paired uniramous, prehensile walking legs attached to the body by broad coxae with spiny gnathobases. The coxae were smaller on the five posterior thoracic somites and the paired appendages were biramous, each bearing a gill supported on a flap attached at its proximal end to the first podomere of the leg. The coxa-body attachment resembles that of modern merostomes and is in advance of trilobites. Evidence suggests that Sidneyia was a bottom-living, carnivorous animal eating larger and harder food than trilobites. Gut contents include ostracodes, hyolithids, small trilobites and phosphatic debris. Sidneyia is the earliest known form which could be an ancestor to merostomes, but its body plan and absence of chelicera distinguishes Sidneyia from this group. The holotype of Amiella ornata Walcott, 1911 is reinterpreted and its synonomy with S. inexpectans is confirmed.

@article{doi101098rstb19810164,
    author = "Bruton, David L.",
    title = "The arthropod Sidneyia inexpectans, Middle Cambrian, Burgess Shale, British Columbia",
    year = "1981",
    journal = "Philosophical transactions of the Royal Society of London. Series B, Biological sciences",
    abstract = "Abstract Old and new specimens of Sidneyia inexpectans have been studied and are accompanied by explanatory drawings and photographs. New reconstructions of the animal are given together with a three-dimensional model. The body consisted of a cephalon with a long backwardly directed doublure, a thorax of nine articulating somites, abdomen with cylindrical exoskeleton of two or three somites and a telson. A caudal fan was formed by a pair of uropods articulating at the posterior margin of the last abdominal somite. The cephalon had stalked eyes and preoral antennae but no walking or grasping appendages. The first four somites of the thorax had paired uniramous, prehensile walking legs attached to the body by broad coxae with spiny gnathobases. The coxae were smaller on the five posterior thoracic somites and the paired appendages were biramous, each bearing a gill supported on a flap attached at its proximal end to the first podomere of the leg. The coxa-body attachment resembles that of modern merostomes and is in advance of trilobites. Evidence suggests that Sidneyia was a bottom-living, carnivorous animal eating larger and harder food than trilobites. Gut contents include ostracodes, hyolithids, small trilobites and phosphatic debris. Sidneyia is the earliest known form which could be an ancestor to merostomes, but its body plan and absence of chelicera distinguishes Sidneyia from this group. The holotype of Amiella ornata Walcott, 1911 is reinterpreted and its synonomy with S. inexpectans is confirmed.",
    url = "https://doi.org/10.1098/rstb.1981.0164",
    doi = "10.1098/rstb.1981.0164",
    openalex = "W1995782650",
    references = "doi101007bf03006730, doi101098rstb19640001, doi101098rstb19750033, doi101111j109636421952tb01854x, doi101111j109636421954tb02211x, doi101111j109636421965tb00500x, doi10182618200049639197506, doi1023072412988, doi104095103458, doi105281zenodo16490103, doi105962bhltitle66889"
}

@inproceedings{whittington1981cambrian90,
    author = "Whittington, H. B",
    title = "Cambrian amimals",
    year = "1981",
    booktitle = "Their ancestors and descendants: Proceedings of the Linnean Society (New South Wales), v. 105, p. 79-87",
    note = "talkorigins\_source = {true}; raw\_reference = {Whittington, H. B., 1981, Cambrian amimals: Their ancestors and descendants: Proceedings of the Linnean Society (New South Wales), v. 105, p. 79-87.}"
}

@article{whittington1981rare89,
    author = "Whittington, H. B",
    title = "Rare arthropods from the Burgess Shale, Middle Cambrian, British Columbia",
    year = "1981",
    journal = "Philosophical Transactions of the Royal Society, London B, v. 292, p. 329-357",
    note = "talkorigins\_source = {true}; raw\_reference = {Whittington, H. B., 1981, Rare arthropods from the Burgess Shale, Middle Cambrian, British Columbia: Philosophical Transactions of the Royal Society, London B, v. 292, p. 329-357.}"
}

@misc{cloud1982the17,
    author = "Cloud, P. and Glaessner, M. F",
    title = "The Ediacarian Period and System",
    year = "1982",
    howpublished = "Metazoa inherit the Earth: Science, v. 217, p. 783-792",
    note = "talkorigins\_source = {true}; raw\_reference = {Cloud, P., and Glaessner, M. F., 1982, The Ediacarian Period and System: Metazoa inherit the Earth: Science, v. 217, p. 783-792.}"
}

@article{conwaymorris1982the31,
    author = "Conway Morris, S. and Robinson, R. A",
    title = "The enigmatic medusoid Peytoia and a comparison of some Cambrian biotas",
    year = "1982",
    journal = "Journal of Paleontology, v. 56, p. 116-122",
    note = "talkorigins\_source = {true}; raw\_reference = {Conway Morris, S., and Robinson, R. A., 1982, The enigmatic medusoid Peytoia and a comparison of some Cambrian biotas: Journal of Paleontology, v. 56, p. 116-122.}"
}

@phdthesis{yankauskas1982upper95,
    author = "Yankauskas, T. V",
    title = "Upper Precambrian and Cambrian plant microfossils of the European USSR and their stratigraphic significance [in Russian] [Ph.D. dissert.]",
    year = "1982",
    publisher = "University of Moscow, Moscow, 52 p",
    note = "talkorigins\_source = {true}; raw\_reference = {Yankauskas, T. V., 1982, Upper Precambrian and Cambrian plant microfossils of the European USSR and their stratigraphic significance [in Russian] [Ph.D. dissert.]: University of Moscow, Moscow, 52 p.}"
}

@article{bengtson1983the5,
    author = "Bengtson, S. and Fletcher, T. P",
    title = "The oldest sequence of skeletal fossils in the Lower Cambrian of southwestern Newfoudland",
    year = "1983",
    journal = "Canadian Journal of Earth Sciences, v. 20, p. 525-536",
    note = "talkorigins\_source = {true}; raw\_reference = {Bengtson, S., and Fletcher, T. P., 1983, The oldest sequence of skeletal fossils in the Lower Cambrian of southwestern Newfoudland: Canadian Journal of Earth Sciences, v. 20, p. 525-536.}"
}

@misc{briggs1983affinities12,
    author = "Briggs, D. E. G",
    title = "Affinities and early evolution of the Crustacea",
    year = "1983",
    howpublished = "The evidence of the Cambrian fossils, in Schram, F. R., ed., Crustacean Phylogeny: Rotterdam, A.A. Balkema, p. 1-22",
    note = "talkorigins\_source = {true}; raw\_reference = {Briggs, D. E. G., 1983, Affinities and early evolution of the Crustacea: The evidence of the Cambrian fossils, in Schram, F. R., ed., Crustacean Phylogeny: Rotterdam, A.A. Balkema, p. 1-22.}"
}

@misc{briggs1983the13,
    author = "Briggs, D. E. G. and Clarkson, E. N. K. and Aldridge, R. J",
    title = "The conodont animal",
    year = "1983",
    howpublished = "Lethaia, v. 16, p. 1-14",
    note = "talkorigins\_source = {true}; raw\_reference = {Briggs, D. E. G., Clarkson, E. N. K., and Aldridge, R. J., 1983, The conodont animal: Lethaia, v. 16, p. 1-14.}"
}

@article{bruton1983emeraldella16,
    author = "Bruton, D. L. and Whittington, H. B",
    title = "Emeraldella and Leancholia, two arthropods from the Burgess Shale, British Columbia",
    year = "1983",
    journal = "Philosophical Transactions of the Royal Society, London B, v. 300, p. 553-585",
    note = "talkorigins\_source = {true}; raw\_reference = {Bruton, D. L., and Whittington, H. B., 1983, Emeraldella and Leancholia, two arthropods from the Burgess Shale, British Columbia: Philosophical Transactions of the Royal Society, London B, v. 300, p. 553-585.}"
}

@misc{collins1983new19,
    author = "Collins, D. H. and Briggs, D. E. G. and Conway Morris, S",
    title = "New Burgess Shale fossil sites reveal Middle Cambrian faunal complex",
    year = "1983",
    howpublished = "Science, v. 222, p. 163-167",
    note = "talkorigins\_source = {true}; raw\_reference = {Collins, D. H., Briggs, D. E. G., and Conway Morris, S., 1983, New Burgess Shale fossil sites reveal Middle Cambrian faunal complex: Science, v. 222, p. 163-167.}"
}

Abstract The type species of two much discussed but hitherto poorly known genera of arthropods are described in detail from new preparations. Illustrations are by photographs, explanatory line drawings, and reconstructions including three-dimensional models. The convex body of Emeraldella brocki was not trilobed, and was divided into a cephalon with labrum and 13 trunk somites, the first 11 having pleurae which were progressively narrower (transversely (tr.)) and more backwardly curved posteriorly, the last two somites being cylindrical, with a long posterior spine inserted into the 13th. A bilobed, spinose, ventral anal plate was probably attached to the 12th somite; the alimentary canal may have terminated in the 13th somite. The cephalon bore long antennae and five pairs of limbs, the first short, uniramous and jointed, the second to fifth biramous, the outer branch elongate-oval and having marginal filaments, the inner branches jointed and progressively longer. Trunk somites 1—11 each bore a pair of biramous limbs, the outer branch bilobed and with filaments on the distal margins, the jointed inner branches long on the anterior six or seven pairs. The coxae of the entire limb series bore a spinose gnathobase on the mesial edge, and the proximal podomeres of the leg branches were spinose. The outer branches were attached to the coxa and possibly the first podomere of the inner leg branch. The maximum known length of the body (excluding the posterior spine) was 65 mm; the animal lacked eyes, and was a benthonic predator and scavenger, walking on and digging into the muddy bottom, the gnathobases enabling soft food to be squeezed, shredded and passed forward along the midline to the backward-facing mouth. The outer branches were presumably gills, and may have aided in feeble swimming. Leanchoilia superlata had a smooth, convex, faintly trilobate exoskeleton. The head shield was subtriangular with an upturned snout. The 11 tergites had broad (tr.) pleurae, behind the fifth progressively narrower (tr.) and more backward-curving; the 11th was curved back beside a short, triangular tail spine, which bore lateral spines. Anteriorly the cephalon bore the great appendage, which consisted of a basal section and four additional stout podomeres shaped to curve through 90°. The second and third podomeres were each extended by a tapering shaft continued by a longer, annulated portion. The distal podomere consisted of a tapering shaft terminating in three claws and a long, annulated extension. The remainder of the body had 13 pairs of biramous appendages (two on the cephalon, one on each trunk somite), the outer branch a lobe having overlapping lamellae on the distal and posterior margins, the inner branch tapering, of some eight podomeres and terminal spines. The proximal portions of the appendages are not preserved, but the outer branch was attached so that the inner branch lay below the anterior border of the outer branch; the two branches were of similar length (tr.) and hung down below the body. The alimentary canal is preserved, filled anteriorly with apatite, the filling showing segmentation and annulation. The mouth was apparently downward- and forward-facing, and led into a bulbous foregut situated beneath the cephalon. The anus opened on the 11th trunk somite. The maximum known length of the body was 68 mm. The animal lacked eyes and was probably benthonic in habit, able to rest on the sediment surface on the great appendage and the tips of the inner branches and to swim over it by metachronal movements of the outer branches (which also acted as gills), the great appendage swung back beneath the body to reduce resistance. It was probably a detritus feeder, the food pushed into the midline by the limbs, the mouth presumably suctorial. There is no evidence of a labrum, or of gnathobasic basal podomeres, but the inner margin of the leg branch was setiferous. The single species of Emeraldella, E.brocki, is recognized, and the type and only specimen of ‘ Emeraldoides ’ is referred to it. Synonymous with Leanchoilia superlata are Walcott’s three species L. major, Bidentia difficilis and Emeraldella micrura, and Simonetta’s Leanchoilia amphiction, L. persephone and L. protogonia. Emeraldellabrocki may be allied with Molaria spinifera; problematical is any relationship to aglaspidids. Leanchoilia superlata may be most closely related to Actaeus armatus. Emeraldella and Leanchoilia are very different from one another, and from either Sidneyia or Naraoia; these four genera are so heterogeneous that Stormer’s grouping of them into the taxon Merostomoidea is rejected as no longer useful.

@article{doi101098rstb19830020,
    author = "Bruton, David L. and Whittington, H. B.",
    title = "Emeraldella and Leanchoilia, two arthropods from the Burgess Shale, Middle Cambrian, British Columbia",
    year = "1983",
    journal = "Philosophical transactions of the Royal Society of London. Series B, Biological sciences",
    abstract = "Abstract The type species of two much discussed but hitherto poorly known genera of arthropods are described in detail from new preparations. Illustrations are by photographs, explanatory line drawings, and reconstructions including three-dimensional models. The convex body of Emeraldella brocki was not trilobed, and was divided into a cephalon with labrum and 13 trunk somites, the first 11 having pleurae which were progressively narrower (transversely (tr.)) and more backwardly curved posteriorly, the last two somites being cylindrical, with a long posterior spine inserted into the 13th. A bilobed, spinose, ventral anal plate was probably attached to the 12th somite; the alimentary canal may have terminated in the 13th somite. The cephalon bore long antennae and five pairs of limbs, the first short, uniramous and jointed, the second to fifth biramous, the outer branch elongate-oval and having marginal filaments, the inner branches jointed and progressively longer. Trunk somites 1—11 each bore a pair of biramous limbs, the outer branch bilobed and with filaments on the distal margins, the jointed inner branches long on the anterior six or seven pairs. The coxae of the entire limb series bore a spinose gnathobase on the mesial edge, and the proximal podomeres of the leg branches were spinose. The outer branches were attached to the coxa and possibly the first podomere of the inner leg branch. The maximum known length of the body (excluding the posterior spine) was 65 mm; the animal lacked eyes, and was a benthonic predator and scavenger, walking on and digging into the muddy bottom, the gnathobases enabling soft food to be squeezed, shredded and passed forward along the midline to the backward-facing mouth. The outer branches were presumably gills, and may have aided in feeble swimming. Leanchoilia superlata had a smooth, convex, faintly trilobate exoskeleton. The head shield was subtriangular with an upturned snout. The 11 tergites had broad (tr.) pleurae, behind the fifth progressively narrower (tr.) and more backward-curving; the 11th was curved back beside a short, triangular tail spine, which bore lateral spines. Anteriorly the cephalon bore the great appendage, which consisted of a basal section and four additional stout podomeres shaped to curve through 90°. The second and third podomeres were each extended by a tapering shaft continued by a longer, annulated portion. The distal podomere consisted of a tapering shaft terminating in three claws and a long, annulated extension. The remainder of the body had 13 pairs of biramous appendages (two on the cephalon, one on each trunk somite), the outer branch a lobe having overlapping lamellae on the distal and posterior margins, the inner branch tapering, of some eight podomeres and terminal spines. The proximal portions of the appendages are not preserved, but the outer branch was attached so that the inner branch lay below the anterior border of the outer branch; the two branches were of similar length (tr.) and hung down below the body. The alimentary canal is preserved, filled anteriorly with apatite, the filling showing segmentation and annulation. The mouth was apparently downward- and forward-facing, and led into a bulbous foregut situated beneath the cephalon. The anus opened on the 11th trunk somite. The maximum known length of the body was 68 mm. The animal lacked eyes and was probably benthonic in habit, able to rest on the sediment surface on the great appendage and the tips of the inner branches and to swim over it by metachronal movements of the outer branches (which also acted as gills), the great appendage swung back beneath the body to reduce resistance. It was probably a detritus feeder, the food pushed into the midline by the limbs, the mouth presumably suctorial. There is no evidence of a labrum, or of gnathobasic basal podomeres, but the inner margin of the leg branch was setiferous. The single species of Emeraldella, E.brocki, is recognized, and the type and only specimen of ‘ Emeraldoides ’ is referred to it. Synonymous with Leanchoilia superlata are Walcott’s three species L. major, Bidentia difficilis and Emeraldella micrura, and Simonetta’s Leanchoilia amphiction, L. persephone and L. protogonia. Emeraldellabrocki may be allied with Molaria spinifera; problematical is any relationship to aglaspidids. Leanchoilia superlata may be most closely related to Actaeus armatus. Emeraldella and Leanchoilia are very different from one another, and from either Sidneyia or Naraoia; these four genera are so heterogeneous that Stormer’s grouping of them into the taxon Merostomoidea is rejected as no longer useful.",
    url = "https://doi.org/10.1098/rstb.1983.0020",
    doi = "10.1098/rstb.1983.0020",
    openalex = "W1994733314",
    references = "doi101038scientificamerican0779122, doi101098rstb19780005, doi101098rstb19810007, doi101098rstb19810164, doi101111j150239311971tb01862x, doi10182618200049639197528, doi10182618200049639197529, doi105281zenodo16490103"
}

Soft-bodied and lightly sclerotized Burgess shale fossils have been found at more than a dozen new localities in an area extending for 20 kilometers along the front of the Cathedral Escarpment in the Middle Cambrian Stephen Formation of the Canadian Rockies. Five different fossil assemblages from four stratigraphic levels have been recognized. These assemblages represent distinct penecontemporaneous marine communities that together make up a normal fore-reef faunal complex.

@article{doi101126science2224620163,
    author = "Collins, Desmond and Briggs, Derek E. G. and Morris, Simon Conway",
    title = "New Burgess Shale Fossil Sites Reveal Middle Cambrian Faunal Complex",
    year = "1983",
    journal = "Science",
    abstract = "Soft-bodied and lightly sclerotized Burgess shale fossils have been found at more than a dozen new localities in an area extending for 20 kilometers along the front of the Cathedral Escarpment in the Middle Cambrian Stephen Formation of the Canadian Rockies. Five different fossil assemblages from four stratigraphic levels have been recognized. These assemblages represent distinct penecontemporaneous marine communities that together make up a normal fore-reef faunal complex.",
    url = "https://doi.org/10.1126/science.222.4620.163",
    doi = "10.1126/science.222.4620.163",
    openalex = "W1994380053",
    references = "doi101017s0094837300006539, doi101038scientificamerican0779122, doi101098rstb19810033, doi101130gsab51731, doi105281zenodo15932730, doi105281zenodo16490103, openalexw2600671946, openalexw2608196808, openalexw614215761"
}

@misc{muller1983crustacea57,
    author = "Muller, K. J",
    title = "Crustacea with preserved soft parts from the Upper Cambrian of Sweden",
    year = "1983",
    howpublished = "Lethaia, v. 16, p. 93-109",
    note = "talkorigins\_source = {true}; raw\_reference = {Muller, K. J., 1983, Crustacea with preserved soft parts from the Upper Cambrian of Sweden: Lethaia, v. 16, p. 93-109.}"
}

@misc{aitken1984the1,
    author = "Aitken, J. D. and McIlreath, J. A",
    title = "The Cathedral Reef escarpment, a Cambrian great wall with humble origins",
    year = "1984",
    howpublished = "Geos: Energy Mines and Resources, Canada, v. 13, no. 1, p. 17-19",
    note = "talkorigins\_source = {true}; raw\_reference = {Aitken, J. D., and McIlreath, J. A., 1984, The Cathedral Reef escarpment, a Cambrian great wall with humble origins: Geos: Energy Mines and Resources, Canada, v. 13, no. 1, p. 17-19.}"
}

Abstract The Lower Cambrian sequence at Nuneaton is outlined, paying particular attention to the 2 m thick Home Farm Member (including the Hyolithes Limestone) and its faunal succession at the type locality, Woodlands Quarry, Hartshill. There follows the first modern description and illustration of microfossils and small shelly fossils from this member. Of thirty-two species covered here, twenty are described and illustrated from Nuneaton for the first time and eight of these are new records. The varied fauna includes phosphatic and calcareous microproblematica (especially Coleoloides typicalis), protoconodonts, agglutinated foraminifera, cap-shaped molluscs, primitive bivalves, hyoliths, inarticulate brachiopods and sponges. The fauna has affinity with fossils in the top Tommotian to lower Atdabanian rocks from Siberia and China, from the Baltic area and the belt from southeast Newfoundland to Massachusetts.

@article{doi101017s0016756800028296,
    author = "Brasier, Martin D.",
    title = "Microfossils and small shelly fossils from the Lower Cambrian Hyolithes Limestone at Nuneaton, English Midlands",
    year = "1984",
    journal = "Geological Magazine",
    abstract = "Abstract The Lower Cambrian sequence at Nuneaton is outlined, paying particular attention to the 2 m thick Home Farm Member (including the Hyolithes Limestone) and its faunal succession at the type locality, Woodlands Quarry, Hartshill. There follows the first modern description and illustration of microfossils and small shelly fossils from this member. Of thirty-two species covered here, twenty are described and illustrated from Nuneaton for the first time and eight of these are new records. The varied fauna includes phosphatic and calcareous microproblematica (especially Coleoloides typicalis), protoconodonts, agglutinated foraminifera, cap-shaped molluscs, primitive bivalves, hyoliths, inarticulate brachiopods and sponges. The fauna has affinity with fossils in the top Tommotian to lower Atdabanian rocks from Siberia and China, from the Baltic area and the belt from southeast Newfoundland to Massachusetts.",
    url = "https://doi.org/10.1017/s0016756800028296",
    doi = "10.1017/s0016756800028296",
    openalex = "W1970229985",
    references = "doi1010160012825280900641, doi101017cbo9781139104067002, doi10108003115517608619064, doi101127zdgg1111959434, doi101139e83050, doi101144gsjgs13130289, doi101144gsljgs1920076010410, doi1023072992311, doi105962bhltitle38279, doi105962bhltitle82327, openalexw2588295003"
}

@misc{muller1984skaracaridae58,
    author = "Muller, K. J. and Walossek, D",
    title = "Skaracaridae, a new order of Crustacea from the Upper Cambrian of Vstergtland, Sweden",
    year = "1984",
    howpublished = "Fossils and Strata (Oslo), v. 17, p. 1-65",
    note = "talkorigins\_source = {true}; raw\_reference = {Muller, K. J., and Walossek, D., 1984, Skaracaridae, a new order of Crustacea from the Upper Cambrian of Vstergtland, Sweden: Fossils and Strata (Oslo), v. 17, p. 1-65.}"
}

@misc{collins1985a18,
    author = "Collins, D. H",
    title = "A new Burgess Shale type fauna in the Middle Cambrian Stephan Formation on Mount Stephan, British Columbia",
    year = "1985",
    howpublished = "In Annual Meeting, Geological Society of America, p.550",
    note = "talkorigins\_source = {true}; raw\_reference = {Collins, D. H., 1985, A new Burgess Shale type fauna in the Middle Cambrian Stephan Formation on Mount Stephan, British Columbia. In Annual Meeting, Geological Society of America, p.550.}"
}

@misc{conwaymorris1985fossils34,
    author = "Conway Morris, S. and Whittington, H. B",
    title = "Fossils of the Burgess Shale. A national treasure in Yoho National Park, British Columbia",
    year = "1985",
    howpublished = "Geological Survey of Canada, Miscellaneous Reports, v. 43, p. 1-31",
    note = "talkorigins\_source = {true}; raw\_reference = {Conway Morris, S., and Whittington, H. B., 1985, Fossils of the Burgess Shale. A national treasure in Yoho National Park, British Columbia: Geological Survey of Canada, Miscellaneous Reports, v. 43, p. 1-31.}"
}

@article{conwaymorris1985the28,
    author = "Conway Morris, S",
    title = "The Middle Cambrian metazoan Wiwaxia corrugata (Matthew) from the Burgess Shale and the Ogygopsis Shale, British Columbia, Canada",
    year = "1985",
    journal = "Philosophical Transactions of the Royal Society, London B, v. 307, p. 507- 582",
    note = "talkorigins\_source = {true}; raw\_reference = {Conway Morris, S., 1985, The Middle Cambrian metazoan Wiwaxia corrugata (Matthew) from the Burgess Shale and the Ogygopsis Shale, British Columbia, Canada: Philosophical Transactions of the Royal Society, London B, v. 307, p. 507- 582.}"
}

@misc{cowie1985late36,
    author = "Cowie, J. W. and Johnson, M. R. W",
    title = "Late Precambrian and Cambrian geological time scale, in Snelling, N. J., ed., The Chronology of the Geological Record, 10 of",
    year = "1985",
    howpublished = "London, Geological Society of London, p. 47- 64",
    note = "talkorigins\_source = {true}; raw\_reference = {Cowie, J. W., and Johnson, M. R. W., 1985, Late Precambrian and Cambrian geological time scale, in Snelling, N. J., ed., The Chronology of the Geological Record, 10 of : London, Geological Society of London, p. 47- 64.}"
}

Abstract A detailed redescription of the Middle Cambrian metazoan Wiwaxia corrugata (Matthew) is given with the aid of photographs, mostly taken under ultraviolet radiation, and explanatory camera lucida drawings. Wiwaxia is known only from the Stephen Formation with four localities within the Bathyuriscus-Elrathina Zone, the celebrated Burgess Shale (Phyllopod bed) and Ogygopsis Shale and two localities that appear to expose strata relatively high in the Formation, and a new locality in the underlying Glossopleura Zone. Specimens from the Ogygopsis Shale consist almost entirely of isolated sclerites, whereas in the Phyllopod bed the species is also known from entire specimens, semi-isolated assemblages and isolated soft-parts. T he description here is based almost entirely on Phyllopod bed m aterial. Wiwaxia was originally largely covered by sclerites. On the basis of shape and arrangement five distinct zones are recognizable: dorsal, upper lateral, lower lateral, anterior and ventro-lateral. In addition, there was a row of elongate dorso-lateral spinose sclerites running along either side of the body. Each sclerite was inserted separately via a root-like structure. Growth of the animal appears to have occurred by moulting of the sclerites; one unique juvenile specimen appears to be preserved in the act of moulting. The ventral surface was apparently an area of soft tissue devoid of sclerites. Little is known of the internal anatomy, although anteriorly there was a feeding apparatus consisting of two rows of posteriorly directed teeth. Most stages of growth are known varying from presumed juveniles, which at their smallest may have lacked spines, to adults over 50 mm long. Wiwaxia appears to have been an epifaunal deposit feeder that crawled across the sea-bed, although smaller juveniles may have been infaunal. The dorso-lateral spines may have provided protection against predators and the existence of broken spines suggests the successful deterrence of attack. The affinities of Wiwaxia do not appear to lie with the polychaetous annelids. While the possibilities of convergence cannot be eliminated, there appears to be a significant similarity between Wiwaxia and molluscs that suggests a related derivation from a turbellarian ancestor. Nevertheless, Wiwaxia has a distinctive bodyplan and as such cannot be accommodated in any known phylum. While Wiwaxia is unique to the Stephen Formation isolated sclerites from Lower Cambrian rocks appear to represent earlier wiwaxiids, although these sclerites show differences in their size and composition as com pared with Wiwaxia. Wiwaxia enhances knowledge of early metazoan evolution and ecology in the Cambrian. In particular, it gives fresh insights into the origin and relative success of certain metazoan bodyplans, the origin of trace fossils, and the importance of predation in Cambrian communities.

@article{doi101098rstb19850005,
    author = "Morris, Simon Conway",
    title = "The Middle Cambrian metazoan Wiwaxia corrugata (Matthew) from the Burgess Shale and Ogygopsis Shale, British Columbia, Canada",
    year = "1985",
    journal = "Philosophical transactions of the Royal Society of London. Series B, Biological sciences",
    abstract = "Abstract A detailed redescription of the Middle Cambrian metazoan Wiwaxia corrugata (Matthew) is given with the aid of photographs, mostly taken under ultraviolet radiation, and explanatory camera lucida drawings. Wiwaxia is known only from the Stephen Formation with four localities within the Bathyuriscus-Elrathina Zone, the celebrated Burgess Shale (Phyllopod bed) and Ogygopsis Shale and two localities that appear to expose strata relatively high in the Formation, and a new locality in the underlying Glossopleura Zone. Specimens from the Ogygopsis Shale consist almost entirely of isolated sclerites, whereas in the Phyllopod bed the species is also known from entire specimens, semi-isolated assemblages and isolated soft-parts. T he description here is based almost entirely on Phyllopod bed m aterial. Wiwaxia was originally largely covered by sclerites. On the basis of shape and arrangement five distinct zones are recognizable: dorsal, upper lateral, lower lateral, anterior and ventro-lateral. In addition, there was a row of elongate dorso-lateral spinose sclerites running along either side of the body. Each sclerite was inserted separately via a root-like structure. Growth of the animal appears to have occurred by moulting of the sclerites; one unique juvenile specimen appears to be preserved in the act of moulting. The ventral surface was apparently an area of soft tissue devoid of sclerites. Little is known of the internal anatomy, although anteriorly there was a feeding apparatus consisting of two rows of posteriorly directed teeth. Most stages of growth are known varying from presumed juveniles, which at their smallest may have lacked spines, to adults over 50 mm long. Wiwaxia appears to have been an epifaunal deposit feeder that crawled across the sea-bed, although smaller juveniles may have been infaunal. The dorso-lateral spines may have provided protection against predators and the existence of broken spines suggests the successful deterrence of attack. The affinities of Wiwaxia do not appear to lie with the polychaetous annelids. While the possibilities of convergence cannot be eliminated, there appears to be a significant similarity between Wiwaxia and molluscs that suggests a related derivation from a turbellarian ancestor. Nevertheless, Wiwaxia has a distinctive bodyplan and as such cannot be accommodated in any known phylum. While Wiwaxia is unique to the Stephen Formation isolated sclerites from Lower Cambrian rocks appear to represent earlier wiwaxiids, although these sclerites show differences in their size and composition as com pared with Wiwaxia. Wiwaxia enhances knowledge of early metazoan evolution and ecology in the Cambrian. In particular, it gives fresh insights into the origin and relative success of certain metazoan bodyplans, the origin of trace fossils, and the importance of predation in Cambrian communities.",
    url = "https://doi.org/10.1098/rstb.1985.0005",
    doi = "10.1098/rstb.1985.0005",
    openalex = "W2165800154",
    references = "doi1010160301926879900226, doi101038285160a0, doi101098rstb19810007, doi101098rstb19810164, doi101111j1469185x1966tb01624x, doi101111j150239311969tb01258x, doi10182618200093301197301, doi102113gsecongeo644383, doi105281zenodo15942062, openalexw1575297980, openalexw3116078484"
}

Abstract The geological setting, biotic diversity and taphonomy of Cambrian soft-bodied Lagerstätten are reviewed with special reference to the Lower Cambrian Emu Bay Shale (South Australia) and Kinzers Formation (Pennsylvania), and the Middle Cambrian Stephen Formation (Burgess Shale and adjacent localities, British Columbia). Brief mention is made also of a number of more minor occurrences in the U.S.A., China and Spain. Exceptional preservation in the Upper Cambrian is discussed by K. J. Müller (this symposium). These soft-bodied Lagerstätten afford a series of special insights into the nature of Cambrian life. Emphasis is laid on the information they provide with regards (i) levels of diversity and the proportion of skeletized taxa; (ii) the origin and relative success of bodyplans; (iii) community ecology and evolution.

@article{doi101098rstb19850138,
    author = "Morris, Simon Conway",
    title = "Cambrian Lagerstätten: their distribution and significance",
    year = "1985",
    journal = "Philosophical transactions of the Royal Society of London. Series B, Biological sciences",
    abstract = "Abstract The geological setting, biotic diversity and taphonomy of Cambrian soft-bodied Lagerstätten are reviewed with special reference to the Lower Cambrian Emu Bay Shale (South Australia) and Kinzers Formation (Pennsylvania), and the Middle Cambrian Stephen Formation (Burgess Shale and adjacent localities, British Columbia). Brief mention is made also of a number of more minor occurrences in the U.S.A., China and Spain. Exceptional preservation in the Upper Cambrian is discussed by K. J. Müller (this symposium). These soft-bodied Lagerstätten afford a series of special insights into the nature of Cambrian life. Emphasis is laid on the information they provide with regards (i) levels of diversity and the proportion of skeletized taxa; (ii) the origin and relative success of bodyplans; (iii) community ecology and evolution.",
    url = "https://doi.org/10.1098/rstb.1985.0138",
    doi = "10.1098/rstb.1985.0138",
    openalex = "W2030057765",
    references = "doi1010160301926885900518, doi101017s0094837300005972, doi101017s0094837300006539, doi101086628416, doi101098rstb19810164, doi101111j1469185x1984tb00411x, doi101111j150239311971tb01864x, doi101130gsab49195, doi1023072412725, doi105962bhltitle66379"
}

@article{robinson1985affinities62,
    author = "Robinson, R. A",
    title = "Affinities of Aysheaia (Onychophora) with a description of a new Cambrian species",
    year = "1985",
    journal = "Journal of Paleontology, v. 59, p. 226-235",
    note = "talkorigins\_source = {true}; raw\_reference = {Robinson, R. A., 1985, Affinities of Aysheaia (Onychophora) with a description of a new Cambrian species: Journal of Paleontology, v. 59, p. 226-235.}"
}

@article{whittington1985extraordinary94,
    author = "Whittington, H. B. and Conway Morris, S",
    title = "Extraordinary Fossil Biotas",
    year = "1985",
    journal = "Their Ecological and Evolutionary Significance: London, Royal Society, 192 p.; Published originally in Philosophical Transactions of the Royal Society, London B 311:1-192",
    note = "talkorigins\_source = {true}; raw\_reference = {Whittington, H. B., and Conway Morris, S., 1985, Extraordinary Fossil Biotas: Their Ecological and Evolutionary Significance: London, Royal Society, 192 p.; Published originally in Philosophical Transactions of the Royal Society, London B 311:1-192.}"
}

@article{whittington1985tegopelte91,
    author = "Whittington, H. B",
    title = "Tegopelte gigas, a second soft-bodied trilobite from the Burgess Shale, Middle Cambrian, British Columbia",
    year = "1985",
    journal = "Journal of Paleontology, v. 59, p. 1251-1274",
    note = "talkorigins\_source = {true}; raw\_reference = {Whittington, H. B., 1985, Tegopelte gigas, a second soft-bodied trilobite from the Burgess Shale, Middle Cambrian, British Columbia: Journal of Paleontology, v. 59, p. 1251-1274.}"
}

@book{whittington1985the92,
    author = "Whittington, H. B",
    title = "The Burgess Shale",
    year = "1985",
    publisher = "New Haven, Connecticut, Yale University Press",
    note = "talkorigins\_source = {true}; raw\_reference = {Whittington, H. B., 1985, The Burgess Shale: New Haven, Connecticut, Yale University Press.}"
}

@article{whittington1985the93,
    author = "Whittington, H. B. and Briggs, D. E. G",
    title = "The largest Cambrian animal, Anomalocaris, Burgess Shale, British Columbia",
    year = "1985",
    journal = "Philosophical Transactions of the Royal Society, London B, v. 309, p. 569-609",
    note = "talkorigins\_source = {true}; raw\_reference = {Whittington, H. B., and Briggs, D. E. G., 1985, The largest Cambrian animal, Anomalocaris, Burgess Shale, British Columbia: Philosophical Transactions of the Royal Society, London B, v. 309, p. 569-609.}"
}

@book{conwaymorris1986middle32,
    author = "Conway Morris, S. and Robinson, R. A",
    title = "Middle Cambrian priapulids and other soft-bodied fossils from Utah and Spain",
    year = "1986",
    publisher = "University of Kansas Paleontological Contributions; Paper 117",
    note = "talkorigins\_source = {true}; raw\_reference = {Conway Morris, S., and Robinson, R. A., 1986, Middle Cambrian priapulids and other soft-bodied fossils from Utah and Spain: University of Kansas Paleontological Contributions; Paper 117.}"
}

@misc{conwaymorris1986the29,
    author = "Conway Morris, S",
    title = "The community structure of the Middle Cambrian phyllopod bed (Burgess Shale)",
    year = "1986",
    howpublished = "Palaeontology, v. 29, p. 423-467",
    note = "talkorigins\_source = {true}; raw\_reference = {Conway Morris, S., 1986, The community structure of the Middle Cambrian phyllopod bed (Burgess Shale): Palaeontology, v. 29, p. 423-467.}"
}

@article{openalexw2754161204,
    author = "Morris, S Conway",
    title = "The community structure of the Middle Cambrian Phyllopod Bed (Burgess Shale)",
    year = "1986",
    journal = "Biodiversity Heritage Library (Smithsonian Institution)",
    openalex = "W2754161204"
}

@misc{rigby1986sponges61,
    author = "Rigby, J. K",
    title = "Sponges of the Burgess Shale (Middle Cambrian) British Columbia",
    year = "1986",
    howpublished = "Palaeontographica Canada, v. 2",
    note = "talkorigins\_source = {true}; raw\_reference = {Rigby, J. K., 1986, Sponges of the Burgess Shale (Middle Cambrian) British Columbia: Palaeontographica Canada, v. 2.}"
}

@article{stokes1986alleged66,
    author = "Stokes, W. L",
    title = "Alleged human footprint from Middle Cambrian strata, Milford County, Utah",
    year = "1986",
    journal = "Journal of Geological Education, v. 34, p. 187-190",
    note = "talkorigins\_source = {true}; raw\_reference = {Stokes, W. L., 1986, Alleged human footprint from Middle Cambrian strata, Milford County, Utah: Journal of Geological Education, v. 34, p. 187-190.}"
}

@misc{anonymous1987yohos3,
    author = "Anonymous",
    title = "Yoho's fossils have world significance",
    year = "1987",
    howpublished = "Yoho National Park Highline",
    note = "talkorigins\_source = {true}; raw\_reference = {Anonymous, 1987, Yoho's fossils have world significance: Yoho National Park Highline.}"
}

@misc{conwaymorris1987a30,
    author = "Conway Morris, S. and Peel, J. S. and Higgins, A. K. and Soper, N. J. and Davis, N. C",
    title = "A Burgess Shale-like fauna from the Lower Cambrian of north Greenland",
    year = "1987",
    howpublished = "Nature, v. 326, p. 181-183",
    note = "talkorigins\_source = {true}; raw\_reference = {Conway Morris, S., Peel, J. S., Higgins, A. K., Soper, N. J., and Davis, N. C., 1987, A Burgess Shale-like fauna from the Lower Cambrian of north Greenland: Nature, v. 326, p. 181-183.}"
}

@article{doi101038326181a0,
    author = "Morris, Simon Conway and Peel, John S. and Higgins, A.K and Soper, Nathaniel J. and Davis, Neil",
    title = "A Burgess shale-like fauna from the Lower Cambrian of North Greenland",
    year = "1987",
    journal = "Nature",
    url = "https://doi.org/10.1038/326181a0",
    doi = "10.1038/326181a0",
    openalex = "W2070517799",
    references = "doi1010160301926885900518, doi101017s009483730001246x, doi101098rstb19780005, doi101098rstb19830020, doi101098rstb19850138, doi101126science2224620163, doi101130gsab49195, doi101146annureves10110179001551, openalexw2603635224, openalexw2754161204, openalexw2944885317"
}

@misc{sunweiguo1987early67,
    author = "Sun Wei-guo, Hou Xian-guang",
    title = "Early Cambrian medusae from Chengjiang, Yunnan, China [in Chinese]",
    year = "1987",
    howpublished = "Acta Palaeontologica Sinica, v. 26, p. 257-270",
    note = "talkorigins\_source = {true}; raw\_reference = {Sun Wei-guo, and Hou Xian-guang, 1987, Early Cambrian medusae from Chengjiang, Yunnan, China [in Chinese]: Acta Palaeontologica Sinica, v. 26, p. 257-270.}"
}

@misc{sunweiguo1987early68,
    author = "Sun Wei-guo, Hou Xian-guang",
    title = "Early Cambrian worms from Chengjiang, Yunnan, China",
    year = "1987",
    howpublished = "Moatianshania Gen. Nov. [in Chinese]: Acta Palaeontologica Sinica, v. 26, p. 299-305",
    note = "talkorigins\_source = {true}; raw\_reference = {Sun Wei-guo, and Hou Xian-guang, 1987, Early Cambrian worms from Chengjiang, Yunnan, China: Moatianshania Gen. Nov. [in Chinese]: Acta Palaeontologica Sinica, v. 26, p. 299-305.}"
}

@misc{xianguang1987early46,
    author = "Xian-guang, Hou",
    title = "Early Cambrian large bivalved arthropods from Chengjiang, Eastern Yunnan [in Chinese]",
    year = "1987",
    howpublished = "Acta Palaeontologica Sinica, v. 26, p. 286-298",
    note = "talkorigins\_source = {true}; raw\_reference = {Hou Xian-guang, 1987, Early Cambrian large bivalved arthropods from Chengjiang, Eastern Yunnan [in Chinese]: Acta Palaeontologica Sinica, v. 26, p. 286-298.}"
}

@misc{xianguang1987three45,
    author = "Xian-guang, Hou",
    title = "Three new large arthropods from Lower Cambrian, Chengjiang, Eastern Yunnan [in Chinese]",
    year = "1987",
    howpublished = "Acta Palaeontologica Sinica, v. 26, p. 272-285",
    note = "talkorigins\_source = {true}; raw\_reference = {Hou Xian-guang, 1987, Three new large arthropods from Lower Cambrian, Chengjiang, Eastern Yunnan [in Chinese]: Acta Palaeontologica Sinica, v. 26, p. 272-285.}"
}

@misc{xianguang1987two44,
    author = "Xian-guang, Hou",
    title = "Two new arthropods from Lower Cambrian, Chengjiang, Eastern Yunnan [in Chinese]",
    year = "1987",
    howpublished = "Acta Palaeontologica Sinica, v. 26, p. 236- 256",
    note = "talkorigins\_source = {true}; raw\_reference = {Hou Xian-guang, 1987, Two new arthropods from Lower Cambrian, Chengjiang, Eastern Yunnan [in Chinese]: Acta Palaeontologica Sinica, v. 26, p. 236- 256.}"
}

@misc{briggs1988a14,
    author = "Briggs, D. E. G. and Collins, D",
    title = "A Middle Cambrian chelicerate from Mount Stephan, British Columbia",
    year = "1988",
    howpublished = "Palaeontology, v. 31, p. 779-798",
    note = "talkorigins\_source = {true}; raw\_reference = {Briggs, D. E. G., and Collins, D., 1988, A Middle Cambrian chelicerate from Mount Stephan, British Columbia: Palaeontology, v. 31, p. 779-798.}"
}

@misc{dzik1988the39,
    author = "Dzik, J. and Lendzion, K",
    title = "The oldest arthropods of the East European platform",
    year = "1988",
    howpublished = "Lethaia, v. 21, p. 29-38",
    note = "talkorigins\_source = {true}; raw\_reference = {Dzik, J., and Lendzion, K., 1988, The oldest arthropods of the East European platform: Lethaia, v. 21, p. 29-38.}"
}

@misc{houxianguang1988discovery47,
    author = "Hou Xian-guang, Sun Wei-guo",
    title = "Discovery of Chengjiang fauna at Meishucun, Jinning, Yunnan [in Chinese]",
    year = "1988",
    howpublished = "Acta Palaeontologica Sinica, v. 27, p. 1-12",
    note = "talkorigins\_source = {true}; raw\_reference = {Hou Xian-guang, and Sun Wei-guo, 1988, Discovery of Chengjiang fauna at Meishucun, Jinning, Yunnan [in Chinese]: Acta Palaeontologica Sinica, v. 27, p. 1-12.}"
}

@article{openalexw2138270429,
    author = "Morris, Simon Conway and Robison, Richard A.",
    title = "More soft-bodied animals and algae from the Middle Cambrian of Utah and British Columbia",
    year = "1988",
    openalex = "W2138270429"
}

Soft-bodied marine faunas from the Lower and Middle Cambrian, exemplified by the Burgess Shale of British Columbia, are a key component in understanding the major adaptive radiations at the beginning of the Phanerozoic ("Cambrian explosion"). These faunas have a widespread distribution, and many taxa have pronounced longevity. Among the components appear to be survivors of the preceding Ediacaran assemblages and a suite of bizarre forms that give unexpected insights into morphological diversification. Microevolutionary processes, however, seem adequate to account for this radiation, and the macroevolutionary patterns that set the seal on Phanerozoic life are contingent on random extinctions. They weeded out the morphological spectrum and permitted rediversification among surviving clades. Although the predictability of which clades will play in successive acts of the Phanerozoic theater is low, at least the outlines of the underlying ecological plot are already clear from the opening of the drama.

@article{doi101126science2464928339,
    author = "Morris, Simon Conway",
    title = "Burgess Shale Faunas and the Cambrian Explosion",
    year = "1989",
    journal = "Science",
    abstract = {Soft-bodied marine faunas from the Lower and Middle Cambrian, exemplified by the Burgess Shale of British Columbia, are a key component in understanding the major adaptive radiations at the beginning of the Phanerozoic ("Cambrian explosion"). These faunas have a widespread distribution, and many taxa have pronounced longevity. Among the components appear to be survivors of the preceding Ediacaran assemblages and a suite of bizarre forms that give unexpected insights into morphological diversification. Microevolutionary processes, however, seem adequate to account for this radiation, and the macroevolutionary patterns that set the seal on Phanerozoic life are contingent on random extinctions. They weeded out the morphological spectrum and permitted rediversification among surviving clades. Although the predictability of which clades will play in successive acts of the Phanerozoic theater is low, at least the outlines of the underlying ecological plot are already clear from the opening of the drama.},
    url = "https://doi.org/10.1126/science.246.4928.339",
    doi = "10.1126/science.246.4928.339",
    openalex = "W2162201296",
    references = "doi1010079781475707403, doi1010160009254187901653, doi1010160301926885900518, doi101017s0094837300006539, doi101038326181a0, doi101098rstb19750033, doi101098rstb19780005, doi101098rstb19850005, doi101098rstb19850138, doi101111j150239311989tb01332x, doi101126science2164542173, doi101126science2224620163, doi101126science22246281123, doi101126science3277277, doi1011300091761319880160149mibbbs23co2, doi101146annureves10110179001551, doi101826182003741571989, dzik1988the, gingerich1987evolution, morris1979the, morris1987a, openalexw2473761340"
}

@misc{gould1989wonderful42,
    author = "Gould, S. J",
    title = "Wonderful Life",
    year = "1989",
    howpublished = "The Burgess Shale and the Nature of History: New York, W. W. Norton",
    note = "talkorigins\_source = {true}; raw\_reference = {Gould, S. J., 1989, Wonderful Life: The Burgess Shale and the Nature of History: New York, W. W. Norton.}"
}

Organic preservation of non-mineralizing animals constitutes an important part of the paleontological record, yet the processes involved have not been investigated in detail. Organic-walled fossils are generally explicable as a coincidence of original, relatively recalcitrant, extra-cellular materials and more or less anti-biotic depositional circumstances. One of the most pervasive natural inhibitors of biodegradation results from substrate and enzyme adsorption onto, and within, clay minerals; such interactions are likely responsible for many of the organic-walled fossils preserved in clastic sediments. Close examination of the fossil Lagerstätte of the Burgess Shale (Middle Cambrian, British Columbia) reveals that most of its so-called soft-bodied fossils are composed of primary (although kerogenized) organic carbon. Their preservation can be attributed to pervasive clay-organic interactions as the organisms were transported in a moving sediment cloud and buried with all cavities and spaces permeated with fine grained clays. The organic-walled Burgess Shale fossils were studied both in petrographic thin section and isolated from the rock matrix, following careful acid maceration. Isotopic analysis of bulk organic and carbonate carbon yielded values consistent with a normal marine paleoenvironment. Anatomical and histological consideration of the enigmatic Burgess worm Amiskwia suggest that it may in fact be a chaetognath, while the putative chordate Pikaia appears not to be related to modern cephalochordates.

@article{doi101017s0094837300009994,
    author = "Butterfield, Nicholas J.",
    title = "Organic preservation of non-mineralizing organisms and the taphonomy of the Burgess Shale",
    year = "1990",
    journal = "Paleobiology",
    abstract = "Organic preservation of non-mineralizing animals constitutes an important part of the paleontological record, yet the processes involved have not been investigated in detail. Organic-walled fossils are generally explicable as a coincidence of original, relatively recalcitrant, extra-cellular materials and more or less anti-biotic depositional circumstances. One of the most pervasive natural inhibitors of biodegradation results from substrate and enzyme adsorption onto, and within, clay minerals; such interactions are likely responsible for many of the organic-walled fossils preserved in clastic sediments. Close examination of the fossil Lagerstätte of the Burgess Shale (Middle Cambrian, British Columbia) reveals that most of its so-called soft-bodied fossils are composed of primary (although kerogenized) organic carbon. Their preservation can be attributed to pervasive clay-organic interactions as the organisms were transported in a moving sediment cloud and buried with all cavities and spaces permeated with fine grained clays. The organic-walled Burgess Shale fossils were studied both in petrographic thin section and isolated from the rock matrix, following careful acid maceration. Isotopic analysis of bulk organic and carbonate carbon yielded values consistent with a normal marine paleoenvironment. Anatomical and histological consideration of the enigmatic Burgess worm Amiskwia suggest that it may in fact be a chaetognath, while the putative chordate Pikaia appears not to be related to modern cephalochordates.",
    url = "https://doi.org/10.1017/s0094837300009994",
    doi = "10.1017/s0094837300009994",
    openalex = "W2484296155",
    references = "allison1988the, doi1010079783642859168, doi1010079783642878138, doi1010079783642964466, doi1010160016703778901990, doi1010160016703781902441, doi1010160020711x85900230, doi101016c20090018339, doi101017s0022336000029905, doi101017s009483730001188x, doi101017s0094837300012082, doi101029pa003i005p00621, doi101038scientificamerican0779122, doi10108003115517908565437, doi101098rstb19850096, doi101126science2464928339, doi101130001676061968791315tailif20co2, doi101146annurevmi41100187002341, doi1015159780691220239, doi1023071484559, doi104095103458, openalexw2240758963, openalexw2598873191, openalexw2944885317, openalexw3025073342, openalexw587905045"
}

A rich assemblage of early Middle Cambrian brachiopods from the ‘first discovery limestone’ of the Coonigan Formation, western N.S.W. contains 20 taxa (eight Articulata, 11 Inarticulata and one which cannot be assigned with certainty to either class). New articulate species are Nisusia grandis grandis, N. grandis glabra, Wimanella tricavata, Arctohedra alata, Acareorthis jelli, Cymbricia spinicostata, Austrohedra mimica and Glaphyrorthis fastigata, with the last four mentioned new genera. Inarticulate taxa include species of Trematosia and?Kutorgina, Hadrotreta primaeva (Walcott), Micromitra nerranubawu Kruse and new species of Kleithriatreta lamellosa, Eothele granulata, Dictyonina australis, Palaeoschmidites horizontalis, Lingulella bynguanoensis, Westonia cymbricensis, and an indeterminate lingulacean; Kleithriatreta is a new genus. The enigmatic new genus and species Bynguanoia perplexa cannot be placed within either the Articulata or Inarticulata. Seven taxa are endemic, six are comparable with taxa from North America, and four with species from the U.S.S.R. The closest correlation, based on three species, is with the Pioche Shale, Nevada, which straddles the Early-Middle Cambrian boundary. The associated trilobite fauna with Redlichia and Pagetia indicates an earliest Middle Cambrian age.

@article{doi10108003115519008619059,
    author = "Roberts, John and Jell, Peter A.",
    title = "Early Middle Cambrian (Ordian) brachiopods of the Coonigan Formation, western New South Wales",
    year = "1990",
    journal = "Alcheringa An Australasian Journal of Palaeontology",
    abstract = "A rich assemblage of early Middle Cambrian brachiopods from the ‘first discovery limestone’ of the Coonigan Formation, western N.S.W. contains 20 taxa (eight Articulata, 11 Inarticulata and one which cannot be assigned with certainty to either class). New articulate species are Nisusia grandis grandis, N. grandis glabra, Wimanella tricavata, Arctohedra alata, Acareorthis jelli, Cymbricia spinicostata, Austrohedra mimica and Glaphyrorthis fastigata, with the last four mentioned new genera. Inarticulate taxa include species of Trematosia and?Kutorgina, Hadrotreta primaeva (Walcott), Micromitra nerranubawu Kruse and new species of Kleithriatreta lamellosa, Eothele granulata, Dictyonina australis, Palaeoschmidites horizontalis, Lingulella bynguanoensis, Westonia cymbricensis, and an indeterminate lingulacean; Kleithriatreta is a new genus. The enigmatic new genus and species Bynguanoia perplexa cannot be placed within either the Articulata or Inarticulata. Seven taxa are endemic, six are comparable with taxa from North America, and four with species from the U.S.S.R. The closest correlation, based on three species, is with the Pioche Shale, Nevada, which straddles the Early-Middle Cambrian boundary. The associated trilobite fauna with Redlichia and Pagetia indicates an earliest Middle Cambrian age.",
    url = "https://doi.org/10.1080/03115519008619059",
    doi = "10.1080/03115519008619059",
    openalex = "W2001653686",
    references = "doi105479si009638011395227, doi105962bhltitle5732, openalexw2598637701"
}

High in the Canadian Rockies is a small limestone quarry formed 530 million years ago called the Burgess Shale. It hold the remains of an ancient sea where dozens of strange creatures lived-a forgotten corner of evolution preserved in awesome detail. In this book Stephen Jay Gould explores what the Burgess Shale tells us about evolution and the nature of history.

@article{doi105860choice273873,
    title = "Wonderful life: the Burgess Shale and the nature of history",
    year = "1990",
    journal = "Choice Reviews Online",
    abstract = "High in the Canadian Rockies is a small limestone quarry formed 530 million years ago called the Burgess Shale. It hold the remains of an ancient sea where dozens of strange creatures lived-a forgotten corner of evolution preserved in awesome detail. In this book Stephen Jay Gould explores what the Burgess Shale tells us about evolution and the nature of history.",
    url = "https://doi.org/10.5860/choice.27-3873",
    doi = "10.5860/choice.27-3873",
    openalex = "W1675572849"
}

The Lower Cambrian Chengjiang fauna is reviewed and shown to be closely comparable with the younger Burgess Shale fauna. but with various differences in detail. A diverse group of more or less annulated lobopod animals including ‘armoured lobopods’ are regarded as representatives of the phylum Onychophora. ‘Trilobitomorphs’ include several new types. Probable protaspides of the trilobitomorph Naraoia are described. No molluses or deuterostomes have been identified. The preservational orientations of the various taxa are reviewed and compared with orientations of the Burgess Shale taxa. Orientation in the sediment is found to be closely correlated to the original shape of individuals. Several new genera and species are described: the segmented. worm‐shaped Yunnanozoon lividum gen. et sp.n., the ‘armoured lobopods’ Onychodictyon ferox gen. et sp.n. and Cardiodictyon catenulum gen. et sp.n. and the arthropods Saperion glumaceum gen. et sp.n., Sinoburius Iunaris gen. et sp.n., and Xandarella spectaculum gen. et sp.n.

@article{doi101111j146364091991tb00303x,
    author = "XIANGUANG, HOU and Ramsköld, Lars and Bergström, Jan",
    title = "Composition and preservation of the Chengjiang fauna –a Lower Cambrian soft‐bodied biota",
    year = "1991",
    journal = "Zoologica Scripta",
    abstract = "The Lower Cambrian Chengjiang fauna is reviewed and shown to be closely comparable with the younger Burgess Shale fauna. but with various differences in detail. A diverse group of more or less annulated lobopod animals including ‘armoured lobopods’ are regarded as representatives of the phylum Onychophora. ‘Trilobitomorphs’ include several new types. Probable protaspides of the trilobitomorph Naraoia are described. No molluses or deuterostomes have been identified. The preservational orientations of the various taxa are reviewed and compared with orientations of the Burgess Shale taxa. Orientation in the sediment is found to be closely correlated to the original shape of individuals. Several new genera and species are described: the segmented. worm‐shaped Yunnanozoon lividum gen. et sp.n., the ‘armoured lobopods’ Onychodictyon ferox gen. et sp.n. and Cardiodictyon catenulum gen. et sp.n. and the arthropods Saperion glumaceum gen. et sp.n., Sinoburius Iunaris gen. et sp.n., and Xandarella spectaculum gen. et sp.n.",
    url = "https://doi.org/10.1111/j.1463-6409.1991.tb00303.x",
    doi = "10.1111/j.1463-6409.1991.tb00303.x",
    openalex = "W2088299548",
    references = "doi101017s0094837300009994, doi101038326181a0, doi101098rstb19810007, doi101111j1469185x1984tb00411x, doi101111j150239311989tb01332x, doi101126science2464928339, doi101826182003741571989, doi1023072992562, doi104095103962, doi105860choice284524, openalexw2138270429, openalexw2240758963, openalexw2754161204"
}

Burgess Shale-type faunas are now known from almost 40 lower and middle Cambrian localities, although those from British Columbia (Canada), Yunnan (China) and Peary Land (Greenland) are of paramount significance. The diverse faunas are dominated by animals with an otherwise negligible fossilization potential, and their stratigraphical position makes them of unique importance in documenting the major adaptive radiations at this time (‘Cambrian explosion’). Important features of these faunas include the presence of taxa surviving from the late Precambrian Ediacaran faunas, the discovery of articulated material that throws new light on scleritome organization in various Cambrian skeletal taxa, and the significance of the degree of anatomical disparity among Cambrian animals. In addition, these soft-bodied faunas offer some hope of reconciling soft-part data with trace fossil occurrences. New discoveries of Burgess Shale-type faunas are inevitable, and such finds will continue to enhance our under­standing of early animal evolution.

@article{doi101144gsjgs14940631,
    author = "Morris, Simon Conway",
    title = "Burgess Shale-type faunas in the context of the ‘Cambrian explosion’: a review",
    year = "1992",
    journal = "Journal of the Geological Society",
    abstract = "Burgess Shale-type faunas are now known from almost 40 lower and middle Cambrian localities, although those from British Columbia (Canada), Yunnan (China) and Peary Land (Greenland) are of paramount significance. The diverse faunas are dominated by animals with an otherwise negligible fossilization potential, and their stratigraphical position makes them of unique importance in documenting the major adaptive radiations at this time (‘Cambrian explosion’). Important features of these faunas include the presence of taxa surviving from the late Precambrian Ediacaran faunas, the discovery of articulated material that throws new light on scleritome organization in various Cambrian skeletal taxa, and the significance of the degree of anatomical disparity among Cambrian animals. In addition, these soft-bodied faunas offer some hope of reconciling soft-part data with trace fossil occurrences. New discoveries of Burgess Shale-type faunas are inevitable, and such finds will continue to enhance our under­standing of early animal evolution.",
    url = "https://doi.org/10.1144/gsjgs.149.4.0631",
    doi = "10.1144/gsjgs.149.4.0631",
    openalex = "W2139980192",
    references = "doi101016003101829390065q, doi1010160092867489909471, doi101038345802a0, doi101111j150239311989tb01332x, doi101111j150239311989tb01679x, doi101126science2464928339, doi101144gsjgs14940607, doi101826182003741571989, doi105860choice273873, openalexw2754161204"
}

The vermiform pedicle is one of the most distinctive organs of modern lingulids, but it is rarely preserved. Only two fossil specimens of lingulids with pedicle casts have been reported, one from the Ordovician and the other from the Devonian. No record of fossil pedicles of Lingulella and Lingulepis, the dominant Cambrian and Early Ordovician lingulids, is known. Fossil lingulids from the Lower Cambrian of Chengjiang County, Yunnan, suggest that the structure and function of the pedicle of the lingulids has not changed significantly from its first appearance. A comparison of fossil pedicle of lingulids from the Lower Cambrian, Chengjiang County (China), the Burgess Shale, Middle Cambrian, British Columbia (Canada), the Trenton Formation, Middle Ordovician, New York (U.S.A.), and the Devonian, Devonshire (England, U.K.) shows that the delthyrial area to which the pedicle muscles are attached was reduced in length through time until these muscles were completely embraced by the two valves. Two species, Lingulella chengjiangensis n. sp. and Lingulepis malongensis Rong, are described.

@article{doi101017s0022336000037057,
    author = "Yugan, Jin and Xianguang, Hou and Huayu, Wang",
    title = "Lower Cambrian pediculate lingulids from Yunnan, China",
    year = "1993",
    journal = "Journal of Paleontology",
    abstract = "The vermiform pedicle is one of the most distinctive organs of modern lingulids, but it is rarely preserved. Only two fossil specimens of lingulids with pedicle casts have been reported, one from the Ordovician and the other from the Devonian. No record of fossil pedicles of Lingulella and Lingulepis, the dominant Cambrian and Early Ordovician lingulids, is known. Fossil lingulids from the Lower Cambrian of Chengjiang County, Yunnan, suggest that the structure and function of the pedicle of the lingulids has not changed significantly from its first appearance. A comparison of fossil pedicle of lingulids from the Lower Cambrian, Chengjiang County (China), the Burgess Shale, Middle Cambrian, British Columbia (Canada), the Trenton Formation, Middle Ordovician, New York (U.S.A.), and the Devonian, Devonshire (England, U.K.) shows that the delthyrial area to which the pedicle muscles are attached was reduced in length through time until these muscles were completely embraced by the two valves. Two species, Lingulella chengjiangensis n. sp. and Lingulepis malongensis Rong, are described.",
    url = "https://doi.org/10.1017/s0022336000037057",
    doi = "10.1017/s0022336000037057",
    openalex = "W2465166802",
    references = "doi101017cbo9781139104036004, doi101017cbo9781139104067002, doi101017s0094837300002979, doi10108000222935608697572, doi101080037454809494387, doi101080037454809496570, doi101098rstb19750033, doi105962bhltitle13172, doi105962bhltitle13182, openalexw2240758963"
}

@article{openalexw2886616075,
    author = "Morris, Simon Conway",
    title = "Ediacaran-like fossils in Cambrian Burgess Shale-type faunas of North America",
    year = "1993",
    journal = "Biodiversity Heritage Library (Smithsonian Institution)",
    openalex = "W2886616075"
}

Abstract Five anomalocaridids are described from the Lower Cambrian Chengjiang fauna of China: Anomalocaris saron sp.n., Anomalocaris sp., Amplectobelua symbrachiata gen. et sp.n., Cucumericrus decoratus gen. et sp.n., and Parapeytoia yunnanensis gen. et sp.n. Ventral trunk appendages are reported for the first time. In C. decoratus and P. yunnanensis, each appendage has a distal segmented walking leg, and a wide lateral extension of a long proximal portion forms the structure previously described as a lateral fin. Furthermore, the structure of the dorsum is elucidated. The supposed ventrolateral gills are flat scales covering the back in transverse rows. The mouth was directed backwards, as in the Middle Cambrian Opabinia regalis, and not directed ventrally as in previous reconstructions. The radial arrangement of the circum‐oral sclerites suggests that anomalocaridids were related to aschelminth worms rather than to arthropods. Hou, X.‐g., Bergström, J. & Ahlberg, P., 1995: Anomalocaris and other large animals in the Lower Cambrian Chengjiang fauna of southwest China. GFF, Vol. 117 (Pt. 3, September), pp. 163–183. Stockholm. ISSN 1103–5897.

@article{doi10108011035899509546213,
    author = "Hou, Xianguang and Bergström, Jan and Ahlberg, Per",
    title = "Anomalocaris and other large animals in the lower Cambrian Chengjiang fauna of southwest China",
    year = "1995",
    journal = "GFF",
    abstract = "Abstract Five anomalocaridids are described from the Lower Cambrian Chengjiang fauna of China: Anomalocaris saron sp.n., Anomalocaris sp., Amplectobelua symbrachiata gen. et sp.n., Cucumericrus decoratus gen. et sp.n., and Parapeytoia yunnanensis gen. et sp.n. Ventral trunk appendages are reported for the first time. In C. decoratus and P. yunnanensis, each appendage has a distal segmented walking leg, and a wide lateral extension of a long proximal portion forms the structure previously described as a lateral fin. Furthermore, the structure of the dorsum is elucidated. The supposed ventrolateral gills are flat scales covering the back in transverse rows. The mouth was directed backwards, as in the Middle Cambrian Opabinia regalis, and not directed ventrally as in previous reconstructions. The radial arrangement of the circum‐oral sclerites suggests that anomalocaridids were related to aschelminth worms rather than to arthropods. Hou, X.‐g., Bergström, J. \& Ahlberg, P., 1995: Anomalocaris and other large animals in the Lower Cambrian Chengjiang fauna of southwest China. GFF, Vol. 117 (Pt. 3, September), pp. 163–183. Stockholm. ISSN 1103–5897.",
    url = "https://doi.org/10.1080/11035899509546213",
    doi = "10.1080/11035899509546213",
    openalex = "W1992001335",
    references = "doi101017s0022336000032145, doi101038114085a0, doi101038337695c0, doi10108003115519608619475, doi101098rstb19810164, doi101098rstb19850096, doi101111j146364091991tb00303x, doi101126science26451631304, doi1023072992562, openalexw3127114020"
}

Abstract Articulated halkieriids of Halkieria evangelista sp. nov. are described from the Sirius Passet fauna in the Lower Cambrian Buen Formation of Peary Land, North Greenland. Three zones of sclerites are recognizable: obliquely inclined rows of dorsal palmates, quincuncially inserted lateral cultrates and imbricated bundles of ventro-lateral siculates. In addition there is a prominent shell at both ends, each with radial ornamentation. Both sclerites and shells were probably calcareous, but increase in body size led to insertion of additional sclerites but marginal accretion of the shells. The ventral sole was soft and, in life, presumably muscular. Recognizable features of internal anatomy include a gut trace and possible musculature, inferred from imprints on the interior of the anterior shell. Halkieriids are closely related to the Middle Cambrian Wixaxia, best known from the Burgess Shale: this clade appears to have played an important role in early protostome evolution. From an animal fairly closely related to Wixaxia arose the polychaete annelids; the bundles of siculate sclerites prefigure the neurochaetae whereas the dorsal notochaetae derive from the palmates. Wixaxia appears to have a relic shell and a similar structure in the sternaspid polychaetes may be an evolutionary remnant. The primitive state in extant polychaetes is best expressed in groups such as chrysopetalids, aphroditaceans and amphinomids. The homology between polychaete chaetae and the mantle setae of brachiopods is one line of evidence to suggest that the latter phylum arose from a juvenile halkieriid in which the posterior shell was first in juxtaposition to the anterior and rotated beneath it to provide the bivalved condition of an ancestral brachiopod. H. evangelista sp. nov. has shells which resemble those of a brachiopod; in particular the posterior one. From predecessors of the halkieriids known as siphogonuchitids it is possible that both chitons (polyplacophorans) and conchiferan molluscs arose. The hypothesis of halkieriids and their relatives having a key role in annelid—brachiopod—mollusc evolution is in accord with some earlier proposals and recent evidence from molecular biology. It casts doubt, however, on a number of favoured concepts including the primitive annelid being oligochaetoid and a burrower, the brachiopods being deuterostomes and the coelom being an archaic feature of metazoans. Rather, the annelid coelom arose as a functional consequence of the transition from a creeping halkieriid to a polychaete with stepping parapodial locomotion.

@article{doi101098rstb19950029,
    author = "Morris, Simon Conway and Peel, John S.",
    title = "Articulated halkieriids from the Lower Cambrian of North Greenland and their role in early protostome evolution",
    year = "1995",
    journal = "Philosophical Transactions of the Royal Society B Biological Sciences",
    abstract = "Abstract Articulated halkieriids of Halkieria evangelista sp. nov. are described from the Sirius Passet fauna in the Lower Cambrian Buen Formation of Peary Land, North Greenland. Three zones of sclerites are recognizable: obliquely inclined rows of dorsal palmates, quincuncially inserted lateral cultrates and imbricated bundles of ventro-lateral siculates. In addition there is a prominent shell at both ends, each with radial ornamentation. Both sclerites and shells were probably calcareous, but increase in body size led to insertion of additional sclerites but marginal accretion of the shells. The ventral sole was soft and, in life, presumably muscular. Recognizable features of internal anatomy include a gut trace and possible musculature, inferred from imprints on the interior of the anterior shell. Halkieriids are closely related to the Middle Cambrian Wixaxia, best known from the Burgess Shale: this clade appears to have played an important role in early protostome evolution. From an animal fairly closely related to Wixaxia arose the polychaete annelids; the bundles of siculate sclerites prefigure the neurochaetae whereas the dorsal notochaetae derive from the palmates. Wixaxia appears to have a relic shell and a similar structure in the sternaspid polychaetes may be an evolutionary remnant. The primitive state in extant polychaetes is best expressed in groups such as chrysopetalids, aphroditaceans and amphinomids. The homology between polychaete chaetae and the mantle setae of brachiopods is one line of evidence to suggest that the latter phylum arose from a juvenile halkieriid in which the posterior shell was first in juxtaposition to the anterior and rotated beneath it to provide the bivalved condition of an ancestral brachiopod. H. evangelista sp. nov. has shells which resemble those of a brachiopod; in particular the posterior one. From predecessors of the halkieriids known as siphogonuchitids it is possible that both chitons (polyplacophorans) and conchiferan molluscs arose. The hypothesis of halkieriids and their relatives having a key role in annelid—brachiopod—mollusc evolution is in accord with some earlier proposals and recent evidence from molecular biology. It casts doubt, however, on a number of favoured concepts including the primitive annelid being oligochaetoid and a burrower, the brachiopods being deuterostomes and the coelom being an archaic feature of metazoans. Rather, the annelid coelom arose as a functional consequence of the transition from a creeping halkieriid to a polychaete with stepping parapodial locomotion.",
    url = "https://doi.org/10.1098/rstb.1995.0029",
    doi = "10.1098/rstb.1995.0029",
    openalex = "W2001586405",
    references = "doi101007978148992427812, doi1010160301926885900518, doi101017s0022336000037057, doi101038326181a0, doi101038345802a0, doi101038361219a0, doi101098rstb19790006, doi101098rstb19850005, doi101111j143904691975tb00509x, doi101111j146363951991tb00312x, doi101111j146364091991tb00303x, doi101111j150239311969tb01258x, doi101111j150239311993tb01502x, doi101126science2224620163, doi101126science2464928339, doi101126science3277277, doi101144gsjgs14940631, doi101146annureves10110179001551, doi105962bhltitle8596, morris1979the, morris1987a, openalexw2138270429, openalexw2302261279, openalexw2754161204, openalexw589153876"
}

Burgess-Shale-type preservation is defined as a taphonomic pathway involving the exceptional organic preservation of non-mineralizing organisms in fully marine siliciclastic sediments. In the Phanerozoic it occurs widely in Lower and Middle Cambrian sequences but subsequently disappears as a significant taphonomic mode. The hypothesis that this distribution derives solely from a secular increase in the depth of bioturbation is falsified: low bioturbation indices do not prevent the rapid enzymatic degradation of organic structure, nor do they account for the conspicuous absence of comparable preservation during the Vendian. An earlier, Late Riphean (ca. 750–850 Ma), interval of enhanced organic-walled fossil preservation suggests a long-term recurrence in Burgess-Shale-type taphonomy that is independent of metazoan activity. A model based on the potentially powerful anti-enzymatic and/or stabilizing effects of clay minerals on organic molecules is proposed to account for Burgess-Shale-type preservation. Long-term changes in average clay mineralogies and the ocean chemistry that determines their interaction with organic molecules are likely to have induced the pronounced secular distribution of these fossil biotas, while regional variations in tectonism, weathering, etc., explain their non-uniform geographic distribution; the close correlation between exceptional, organic-walled fossil preservation and volcano-genic sedimentation in Tertiary lake deposits provides a compelling analogue. Recognition of a temporal control on Burgess-Shale-type preservation constrains the evolutionary scenarios that can be drawn from such biotas; significantly, neither the initial rate of appearance, nor the ultimate fate of Burgess-Shale-type taxa can be directly assessed. □Taphonomy, exceptional preservation, organic preservation, fossil Lagerstatten, Burgess Shale, clay mineralogy, clay-organic interactions, secular change, Cambrian, Proterozoic.

@article{doi101111j150239311995tb01587x,
    author = "Butterfield, Nicholas J.",
    title = "Secular distribution of Burgess‐Shale‐type preservation",
    year = "1995",
    journal = "Lethaia",
    abstract = "Burgess-Shale-type preservation is defined as a taphonomic pathway involving the exceptional organic preservation of non-mineralizing organisms in fully marine siliciclastic sediments. In the Phanerozoic it occurs widely in Lower and Middle Cambrian sequences but subsequently disappears as a significant taphonomic mode. The hypothesis that this distribution derives solely from a secular increase in the depth of bioturbation is falsified: low bioturbation indices do not prevent the rapid enzymatic degradation of organic structure, nor do they account for the conspicuous absence of comparable preservation during the Vendian. An earlier, Late Riphean (ca. 750–850 Ma), interval of enhanced organic-walled fossil preservation suggests a long-term recurrence in Burgess-Shale-type taphonomy that is independent of metazoan activity. A model based on the potentially powerful anti-enzymatic and/or stabilizing effects of clay minerals on organic molecules is proposed to account for Burgess-Shale-type preservation. Long-term changes in average clay mineralogies and the ocean chemistry that determines their interaction with organic molecules are likely to have induced the pronounced secular distribution of these fossil biotas, while regional variations in tectonism, weathering, etc., explain their non-uniform geographic distribution; the close correlation between exceptional, organic-walled fossil preservation and volcano-genic sedimentation in Tertiary lake deposits provides a compelling analogue. Recognition of a temporal control on Burgess-Shale-type preservation constrains the evolutionary scenarios that can be drawn from such biotas; significantly, neither the initial rate of appearance, nor the ultimate fate of Burgess-Shale-type taxa can be directly assessed. □Taphonomy, exceptional preservation, organic preservation, fossil Lagerstatten, Burgess Shale, clay mineralogy, clay-organic interactions, secular change, Cambrian, Proterozoic.",
    url = "https://doi.org/10.1111/j.1502-3931.1995.tb01587.x",
    doi = "10.1111/j.1502-3931.1995.tb01587.x",
    openalex = "W1993033956",
    references = "doi1010079783642748646, doi1010079783642859168, doi101016001174716890051x, doi1010160016703777900473, doi101017cbo9780511601064, doi101038308231a0, doi101038326181a0, doi101038335142a0, doi101038370549a0, doi10108003115517908565437, doi101098rstb19830020, doi101098rstb19850134, doi101111j146364091991tb00303x, doi101126science11539488, doi101126science2224620163, doi101130gsab49195, doi101144gslmem19900120105, doi1015159780691220239, doi10182618200374874199301, dzik1988the, morris1987a"
}

The Mickwitzia sandstone, south-central Sweden, consists of about 10 m of Lower Cambrian clastic sediments deposited in an epicontinental setting. An in formal, lithologically based subdivision, A-E, is introduced. A thin basal conglomerate (interval A) is followed by thin-bedded sand and siltstone with c1ayey partings (interval B and D) and medium-grained sandstone (interval C), largely representing subtidal storm deposits. Interval E consists of thick-bedded shoreface deposits. Heterolithic intervals have well-preserved trace fossils, including Cruziana, Rusophycus, Gyrolithes, Treptichnus and Teichichnus. Beds with impure, often weakly cemented sandstone (interval C) have Rhizocorallium, Monocraterion and Skolithos. Trace fossils are dominated by infaunal feeding and feeding?-dwelling burrows; 40 ichnotaxa are recognized, representing the activity of but a few types of animals. The type material of Monocraterion tentaculatum Torell, 1870, is illustrated for the first time, and the relationship of Monocraterion to Skolithos and Rosselia is discussed. Previously poorly known taxa are described. Scotolithus mirabilis Linnarsson, 1871, consists of a vertical shaft which in its lower part diverges into a wide broom-shaped arrangement. Spiroscolex spiralis (Torell, 1870) is a little-used name for burrows identical to Gyrolithes polonicus. Halopoa imbricata Torell, 1870, is a burrow related to Palaeophycus sulcatus, with a morphology dependant on sediment consistency: it is here assigned to Palaeophycus imbricatus. Fraena tenella Linnarsson, 1871, is assigned to Cruziana and considered a subjective senior synonym of Cruziana problematica. Phycodes pedum Seilacher, 1955, should be assigned to Treptichnus.

@incollection{doi10182618200376656199701,
    author = "Jensen, Sören",
    title = "Trace fossils from the Lower Cambrian Mickwitzia sandstone, south-central Sweden",
    year = "1997",
    booktitle = "Fossils and strata",
    abstract = "The Mickwitzia sandstone, south-central Sweden, consists of about 10 m of Lower Cambrian clastic sediments deposited in an epicontinental setting. An in formal, lithologically based subdivision, A-E, is introduced. A thin basal conglomerate (interval A) is followed by thin-bedded sand and siltstone with c1ayey partings (interval B and D) and medium-grained sandstone (interval C), largely representing subtidal storm deposits. Interval E consists of thick-bedded shoreface deposits. Heterolithic intervals have well-preserved trace fossils, including Cruziana, Rusophycus, Gyrolithes, Treptichnus and Teichichnus. Beds with impure, often weakly cemented sandstone (interval C) have Rhizocorallium, Monocraterion and Skolithos. Trace fossils are dominated by infaunal feeding and feeding?-dwelling burrows; 40 ichnotaxa are recognized, representing the activity of but a few types of animals. The type material of Monocraterion tentaculatum Torell, 1870, is illustrated for the first time, and the relationship of Monocraterion to Skolithos and Rosselia is discussed. Previously poorly known taxa are described. Scotolithus mirabilis Linnarsson, 1871, consists of a vertical shaft which in its lower part diverges into a wide broom-shaped arrangement. Spiroscolex spiralis (Torell, 1870) is a little-used name for burrows identical to Gyrolithes polonicus. Halopoa imbricata Torell, 1870, is a burrow related to Palaeophycus sulcatus, with a morphology dependant on sediment consistency: it is here assigned to Palaeophycus imbricatus. Fraena tenella Linnarsson, 1871, is assigned to Cruziana and considered a subjective senior synonym of Cruziana problematica. Phycodes pedum Seilacher, 1955, should be assigned to Treptichnus.",
    url = "https://doi.org/10.18261/8200376656-1997-01",
    doi = "10.18261/8200376656-1997-01",
    openalex = "W4385643405",
    references = "bridge1985unusual, doi10100797814757131762, doi1010160012825283900223, doi1010160025322767900515, doi1010160031018279901123, doi1010160037073884900034, doi1010160191814182900463, doi10108003115518908527821, doi101111j136530911977tb00134x, doi101111j150239311969tb01258x, doi101111j150239311980tb00632x, doi101126science22246281123, doi10113000167606198293663hssoiv20co2, doi101139e87124, doi101306212f7e4b2b2411d78648000102c1865d, doi101306212f89c22b2411d78648000102c1865d, doi10182618200049639197506, doi10182618200093301197301, doi10182618200374254198901, doi10182618200374742199101, doi1023073514911, doi105281zenodo15992748, doi105860choice304422, openalexw2344228935, openalexw2603635224, openalexw3116078484, openalexw3126336940, openalexw353142951, openalexw574363047, roberts1982facies"
}

Although the evolutionary importance of the Burgess Shale is universally acknowledged, there is disagreement on the mode of preservation of the fossils after burial. Elemental mapping demonstrates that the relative abundance of elements varies between different anatomical features of the specimens. These differences reflect the compositions of the minerals that replicated the decaying organism, which were controlled by contrasts in tissue chemistry. Delicate morphological details are replicated in the elemental maps, showing that authigenic mineralization was fundamental to preserving these fossils, even though some organic remains are also present.

@article{doi101126science28153801173,
    author = "Orr, Patrick J. and Briggs, Derek E. G. and Kearns, Stuart",
    title = "Cambrian Burgess Shale Animals Replicated in Clay Minerals",
    year = "1998",
    journal = "Science",
    abstract = "Although the evolutionary importance of the Burgess Shale is universally acknowledged, there is disagreement on the mode of preservation of the fossils after burial. Elemental mapping demonstrates that the relative abundance of elements varies between different anatomical features of the specimens. These differences reflect the compositions of the minerals that replicated the decaying organism, which were controlled by contrasts in tissue chemistry. Delicate morphological details are replicated in the elemental maps, showing that authigenic mineralization was fundamental to preserving these fossils, even though some organic remains are also present.",
    url = "https://doi.org/10.1126/science.281.5380.1173",
    doi = "10.1126/science.281.5380.1173",
    openalex = "W2120485330",
    references = "briggs1994decay, doi1010160009254187901653, doi101016s0065211308602667, doi101017s0094837300009994, doi101098rsta19840036, doi101098rstb19950029, doi101126science27052401319, doi101139e85204, doi105860choice300309, openalexw2754161204"
}

Abstract This paper presents new ideas on the Early Palaeozoic geography and tectonic history of the Iapetus Ocean involved in the formation of the northern Appalachian-British Caledonide Orogen. Based on an extensive compilation of data along the length of the orogen, particularly using well-preserved relationships in Newfoundland as a template, we show that this orogen may have experienced a very complicated tectonic evolution that resembles parts of the present west and southwest Pacific Ocean in its tectonic complexities. Closure of the west and southwest Pacific Ocean by forward modelling of the oblique collision between Australia and Asia shows that transpressional flattening and non-coaxial strain during terminal collision may impose a deceptively simple linearity and zonation to the resultant orogen and, hence, may produce a linear orogen like the Appalachian-Caledonian Belt. Oceanic elements may preserve along-strike coherency for up to several thousands of kilometres, but excision and strike-slip duplication, as a result of oblique convergence and terminal collisional processes, is expected to obscure elucidation of the intricacies of their accretion and collisional processes. Applying these lessons to the northern Appalachian-Caledonian belt, we rely principally on critical relationships preserved in different parts of the orogen to constrain tectonic models of kinematically-related rock assemblages. The rift-drift transition, and opening of the Iapetus Ocean took place between c. 590–550 Ma. Opening of Iapetus was temporally and spatially related to final closure of the Brazilide Ocean and amalgamation of Gondwanaland. During the Early Ordovician, the Laurentian margin experienced obduction of young, supra-subduction-zone oceanic lithosphere along the length of the northern Appalachian-British Caledonian Belt. Remnants of this lithosphere are best preserved in western Newfoundland and are referred to as the Baie Verte Oceanic Tract. Convergence between Laurentia and the Baie Verte Oceanic Tract was probably dextrally oblique. Slab break-off and a subsequent subduction polarity reversal produced a continental magmatic arc, the Notre Dame Arc, on the edge of the composite Laurentian margin. The Notre Dame Arc was mainly active during the late Tremadoc-Caradoc interval and was flanked by a southeast- or south-facing accretionary complex, the Annieopsquotch Accretionary Tract. Southerly drift of Laurentia to intermediate latitudes of c. 20–25°S was associated with the compressive (Andean) nature of the arc and the accompanying backthrusting of the already-accreted Baie Verte Oceanic Tract further onto the Laurentian foreland. Equivalents of the Notre Dame Arc and its forearc elements in the British Isles have been preserved as independent slices in the Midland Valley and possibly the Northern Belt of the Southern Uplands. During the late Tremadoc (c. 485 Ma), the passive margin on the eastern side of Iapetus also experienced obduction of primitive oceanic arc lithosphere. This arc is referred to as the Penobscot Arc. The eastern passive margin was built upon a Gondwanan fragment (Ganderia) that rifted off Amazonia during the Early Ordovician and probably travelled together with the Avalonian terranes as one microcontinent. The departure of Ganderia and Avalonia from Gondwana opened the Rheic Ocean. Equivalents of the Penobscot Arc may be preserved in New Brunswick and Maine, Leinster in eastern Ireland, and Anglesey in Wales. An arc-polarity reversal along the Ganderian margin after the soft Penobscot collision produced a new arc: the west-facing Popelogan-Victoria Arc, which probably formed a continuous arc system with the Bronson Hill Arc in New England. The Popelogan-Victoria Arc transgressed from a continental to an oceanic substrate from southern to northeastern Newfoundland. Rapid roll-back rifted the Popelogan-Victoria Arc away from Ganderia during the late Arenig (c. 473 Ma) and opened a wide back-arc basin; the Tetagouche-Exploits back-arc basin. The Popelogan-Victoria Arc was accreted sinistrally oblique to the Notre Dame Arc and, by implication, Laurentia during the Late Ordovician. After accretion, the northwestward-dipping subduction zone stepped eastwards into the Tetagouche-Exploits back-arc basin. Equivalents of the Popelogan-Victoria Arc in the British Isles may be preserved as small remnants in the Longford Down Inlier in Ireland. The Longford Down Arc is not preserved in Scotland, although its presence has been inferred there on the tenuous basis of arc detritus. The suture between the Notre Dame Arc and the Popelogan-Victoria-Longford Down Arc system is the Red Indian Line in the Northern Appalachians, but in the British Isles the position is not clear. The fault-bounded Grangegeeth Arc terrane in eastern Ireland, immediately to the south of the Longford Down inlier, may be a displaced piece of the Popelogan-Victoria-Longford Down Arc system. Diachronous closure of the Tetagouche-Exploits basin during the Ashgill to the Wenlock finally caused the collision between Ganderia/Avalonia and Laurentia, whereas the Lake District Arc is related to an earlier closure of the Tornquist Sea between Baltica and Avalonia. After arrival of Avalonia at the Laurentian margin, continuous, dextral oblique convergence between Gondwana and Laurentia was accommodated by another northwest-dipping subduction zone, this time in the Rheic Ocean. The Acadian orogeny in both North America and the British Isles occurred in the Early to Mid-Devonian and is probably related to the collision of Gondwana and/or peri-Gondwanan elements (Meguma, Armorica etc.) with the northern continents.

@article{doi101144gslsp19981430117,
    author = "van Staal, Cees R. and Dewey, John and Niocaill, Conall Mac and McKerrow, W. S.",
    title = "The Cambrian-Silurian tectonic evolution of the northern Appalachians and British Caledonides: history of a complex, west and southwest Pacific-type segment of Iapetus",
    year = "1998",
    journal = "Geological Society London Special Publications",
    abstract = "Abstract This paper presents new ideas on the Early Palaeozoic geography and tectonic history of the Iapetus Ocean involved in the formation of the northern Appalachian-British Caledonide Orogen. Based on an extensive compilation of data along the length of the orogen, particularly using well-preserved relationships in Newfoundland as a template, we show that this orogen may have experienced a very complicated tectonic evolution that resembles parts of the present west and southwest Pacific Ocean in its tectonic complexities. Closure of the west and southwest Pacific Ocean by forward modelling of the oblique collision between Australia and Asia shows that transpressional flattening and non-coaxial strain during terminal collision may impose a deceptively simple linearity and zonation to the resultant orogen and, hence, may produce a linear orogen like the Appalachian-Caledonian Belt. Oceanic elements may preserve along-strike coherency for up to several thousands of kilometres, but excision and strike-slip duplication, as a result of oblique convergence and terminal collisional processes, is expected to obscure elucidation of the intricacies of their accretion and collisional processes. Applying these lessons to the northern Appalachian-Caledonian belt, we rely principally on critical relationships preserved in different parts of the orogen to constrain tectonic models of kinematically-related rock assemblages. The rift-drift transition, and opening of the Iapetus Ocean took place between c. 590–550 Ma. Opening of Iapetus was temporally and spatially related to final closure of the Brazilide Ocean and amalgamation of Gondwanaland. During the Early Ordovician, the Laurentian margin experienced obduction of young, supra-subduction-zone oceanic lithosphere along the length of the northern Appalachian-British Caledonian Belt. Remnants of this lithosphere are best preserved in western Newfoundland and are referred to as the Baie Verte Oceanic Tract. Convergence between Laurentia and the Baie Verte Oceanic Tract was probably dextrally oblique. Slab break-off and a subsequent subduction polarity reversal produced a continental magmatic arc, the Notre Dame Arc, on the edge of the composite Laurentian margin. The Notre Dame Arc was mainly active during the late Tremadoc-Caradoc interval and was flanked by a southeast- or south-facing accretionary complex, the Annieopsquotch Accretionary Tract. Southerly drift of Laurentia to intermediate latitudes of c. 20–25°S was associated with the compressive (Andean) nature of the arc and the accompanying backthrusting of the already-accreted Baie Verte Oceanic Tract further onto the Laurentian foreland. Equivalents of the Notre Dame Arc and its forearc elements in the British Isles have been preserved as independent slices in the Midland Valley and possibly the Northern Belt of the Southern Uplands. During the late Tremadoc (c. 485 Ma), the passive margin on the eastern side of Iapetus also experienced obduction of primitive oceanic arc lithosphere. This arc is referred to as the Penobscot Arc. The eastern passive margin was built upon a Gondwanan fragment (Ganderia) that rifted off Amazonia during the Early Ordovician and probably travelled together with the Avalonian terranes as one microcontinent. The departure of Ganderia and Avalonia from Gondwana opened the Rheic Ocean. Equivalents of the Penobscot Arc may be preserved in New Brunswick and Maine, Leinster in eastern Ireland, and Anglesey in Wales. An arc-polarity reversal along the Ganderian margin after the soft Penobscot collision produced a new arc: the west-facing Popelogan-Victoria Arc, which probably formed a continuous arc system with the Bronson Hill Arc in New England. The Popelogan-Victoria Arc transgressed from a continental to an oceanic substrate from southern to northeastern Newfoundland. Rapid roll-back rifted the Popelogan-Victoria Arc away from Ganderia during the late Arenig (c. 473 Ma) and opened a wide back-arc basin; the Tetagouche-Exploits back-arc basin. The Popelogan-Victoria Arc was accreted sinistrally oblique to the Notre Dame Arc and, by implication, Laurentia during the Late Ordovician. After accretion, the northwestward-dipping subduction zone stepped eastwards into the Tetagouche-Exploits back-arc basin. Equivalents of the Popelogan-Victoria Arc in the British Isles may be preserved as small remnants in the Longford Down Inlier in Ireland. The Longford Down Arc is not preserved in Scotland, although its presence has been inferred there on the tenuous basis of arc detritus. The suture between the Notre Dame Arc and the Popelogan-Victoria-Longford Down Arc system is the Red Indian Line in the Northern Appalachians, but in the British Isles the position is not clear. The fault-bounded Grangegeeth Arc terrane in eastern Ireland, immediately to the south of the Longford Down inlier, may be a displaced piece of the Popelogan-Victoria-Longford Down Arc system. Diachronous closure of the Tetagouche-Exploits basin during the Ashgill to the Wenlock finally caused the collision between Ganderia/Avalonia and Laurentia, whereas the Lake District Arc is related to an earlier closure of the Tornquist Sea between Baltica and Avalonia. After arrival of Avalonia at the Laurentian margin, continuous, dextral oblique convergence between Gondwana and Laurentia was accommodated by another northwest-dipping subduction zone, this time in the Rheic Ocean. The Acadian orogeny in both North America and the British Isles occurred in the Early to Mid-Devonian and is probably related to the collision of Gondwana and/or peri-Gondwanan elements (Meguma, Armorica etc.) with the northern continents.",
    url = "https://doi.org/10.1144/gsl.sp.1998.143.01.17",
    doi = "10.1144/gsl.sp.1998.143.01.17",
    openalex = "W1992871671",
    references = "doi1010160012825296000086, doi101029jb077i023p04432, doi101038001534a0, doi101038224125a0, doi101038279590a0, doi101111j1365246x1990tb06579x, doi101126science25250111409, doi1011300016760619921041621szieft23co2, doi101130dnaggnaf2, doi101144gslmem19900120101, doi10230730067723"
}

INTRODUCTION 1. SETTING THE SCENE 2. THE DISCOVERY OF THE BURGESS SHALE 3. JOURNEY TO THE BURGESS SHALE 4. THE SEARCH FOR NEW BURGESS SHALES 5. THE SIGNIFICANCE OF THE BURGESS SHALE 6. THE ORIGIN OF PHYLA 7. OTHER WORLDS 8. THE LAST WORD ACKNOWLEDGEMENTS APPENDIX 1: FURTHER READING APPENDIX 2: EXHIBITIONS APPENDIX 3: LOCALITIES GLOSSARY INDEX.

@book{openalexw2134978213,
    author = "Conway, Morris",
    title = "The crucible of creation: the Burgess Shale and the rise of animals",
    year = "1998",
    booktitle = "Oxford University Press eBooks",
    abstract = "INTRODUCTION 1. SETTING THE SCENE 2. THE DISCOVERY OF THE BURGESS SHALE 3. JOURNEY TO THE BURGESS SHALE 4. THE SEARCH FOR NEW BURGESS SHALES 5. THE SIGNIFICANCE OF THE BURGESS SHALE 6. THE ORIGIN OF PHYLA 7. OTHER WORLDS 8. THE LAST WORD ACKNOWLEDGEMENTS APPENDIX 1: FURTHER READING APPENDIX 2: EXHIBITIONS APPENDIX 3: LOCALITIES GLOSSARY INDEX.",
    openalex = "W2134978213"
}

Five new bivalved arthropods are described from the Lower Cambrian Chengjiang fauna, Yunnan, China. All of them are rare in the fauna, represented by one or two individuals among thousands of specimens. Four of the five new taxa are preserved with soft parts that show a clear distinction between them. The new taxa provide new important information concerning the soft bodied and limb characters of the early bivalved arthropods. A significant lesson is that, not knowing any soft parts, it is virtually impossible to place systematically a new type of bivalved carapace. It is often impossible even to tell if it is a crustacean or not. A second antenna in the shape of a “great appendage” is identified for the first time among the bivalved arthropods. The new taxa include representatives of the order Pectocaridida, the families Pectocarididae, Clypecarididae and Occacarididae, the genera and species Pectocaris spatiosa, Clypecaris pteroidea, Occacaris oviformis, Forfexicaris valida and Yunnanocaris megista.

@article{doi101017s002233600002758x,
    author = "Hou, Xianguang",
    title = "New rare bivalved arthropods from the Lower Cambrian Chengjiang fauna, Yunnan, China",
    year = "1999",
    journal = "Journal of Paleontology",
    abstract = "Five new bivalved arthropods are described from the Lower Cambrian Chengjiang fauna, Yunnan, China. All of them are rare in the fauna, represented by one or two individuals among thousands of specimens. Four of the five new taxa are preserved with soft parts that show a clear distinction between them. The new taxa provide new important information concerning the soft bodied and limb characters of the early bivalved arthropods. A significant lesson is that, not knowing any soft parts, it is virtually impossible to place systematically a new type of bivalved carapace. It is often impossible even to tell if it is a crustacean or not. A second antenna in the shape of a “great appendage” is identified for the first time among the bivalved arthropods. The new taxa include representatives of the order Pectocaridida, the families Pectocarididae, Clypecarididae and Occacarididae, the genera and species Pectocaris spatiosa, Clypecaris pteroidea, Occacaris oviformis, Forfexicaris valida and Yunnanocaris megista.",
    url = "https://doi.org/10.1017/s002233600002758x",
    doi = "10.1017/s002233600002758x",
    openalex = "W2341789411",
    references = "doi101016003101829390065q, doi10108011035899509546213, doi101098rstb19780005, doi101098rstb19810007, doi101111j146364091991tb00303x, doi101111j150239311990tb01373x, doi101826182003769311997, doi1023072992562, openalexw2205767785"
}

An updated reconstruction of the body plan, functional anatomy and life attitude of the bradoriid arthropod Kunmingella is proposed, based on new fossil specimens with preserved soft parts found in the lower Cambrian of Chengjiang and Haikou (Yunnan, SW China) and on previous evidence. The animal has a single pair of short antennae pointing towards the front (a setal pattern indicates a possible sensory function). The following set of seven appendages (each composed of a 5-segmented endopod and a leaf-like exopod fringed with setae) is poorly differentiated, except the first three pairs (with possible rake-like endopodial outgrowths, smaller exopods) and the last pair of appendages (endopod with longer and more slender podomeres). The endopods are interpreted as walking legs with a possible role in handling food particles (marginal outgrowth with setae). The leaf-like exopods may have had a respiratory function. The trunk end is short, pointed, flanked with furcal-like rami and projects beyond the posterior margin of the carapace. The attachment of the body to the exoskeleton is probably cephalic and apparently lacks any well-developed adductor muscle system. The inferred life attitude of Kunmingella (e.g. crawling on the surface of the sediment) was that of a dorsoventrally flattened arthropod capped by a folded dorsal shield (ventral gape at least 120°), thus resembling the living ostracode Manawa. The animal was also probably able to close its carapace as a response to environmental stress or to survive unfavourable conditions (e.g. buried in sediment). The anterior lobes of the valves are likely to have accommodated visual organs (possibly lensless receptors perceiving ambient light through the translucent head shield). Preserved eggs or embryos suggest a possible ventral brood care. The presence of Kunmingella in coprolites and its numerical abundance in Chengjiang sediment indicate that bradoriids constituted an important source of food for larger predators. Kunmingella differs markedly from the representatives of the crown group Crustacea (extant and Cambrian taxa) and from the stem group derivatives of Crustacea (exemplified by phosphatocopids and some ‘Orsten’ taxa) in showing no major sign of limb specialization (e.g. related to feeding strategies). Although it resembles other Chengjiang euarthropods in important aspects of its body plan (e.g. uniramous antennae, endopod/exopod configuration), Kunmingella possesses several features (e.g. antennal morphology, post-antennular appendages with 5-segmented endopods) which support the view that bradoriids may be very early derivatives of the stem line Crustacea.

@article{doi101111j150239311999tb00547x,
    author = "Shu, Degan and Vannier, Jean and Luo, Huilin and Chen, Ling and Zhang, Xingliang and Hu, Shixue",
    title = "Anatomy and lifestyle of Kunmingella (Arthropoda, Bradoriida) from the Chengjiang fossil Lagerstätte (lower Cambrian; Southwest China)",
    year = "1999",
    journal = "Lethaia",
    abstract = "An updated reconstruction of the body plan, functional anatomy and life attitude of the bradoriid arthropod Kunmingella is proposed, based on new fossil specimens with preserved soft parts found in the lower Cambrian of Chengjiang and Haikou (Yunnan, SW China) and on previous evidence. The animal has a single pair of short antennae pointing towards the front (a setal pattern indicates a possible sensory function). The following set of seven appendages (each composed of a 5-segmented endopod and a leaf-like exopod fringed with setae) is poorly differentiated, except the first three pairs (with possible rake-like endopodial outgrowths, smaller exopods) and the last pair of appendages (endopod with longer and more slender podomeres). The endopods are interpreted as walking legs with a possible role in handling food particles (marginal outgrowth with setae). The leaf-like exopods may have had a respiratory function. The trunk end is short, pointed, flanked with furcal-like rami and projects beyond the posterior margin of the carapace. The attachment of the body to the exoskeleton is probably cephalic and apparently lacks any well-developed adductor muscle system. The inferred life attitude of Kunmingella (e.g. crawling on the surface of the sediment) was that of a dorsoventrally flattened arthropod capped by a folded dorsal shield (ventral gape at least 120°), thus resembling the living ostracode Manawa. The animal was also probably able to close its carapace as a response to environmental stress or to survive unfavourable conditions (e.g. buried in sediment). The anterior lobes of the valves are likely to have accommodated visual organs (possibly lensless receptors perceiving ambient light through the translucent head shield). Preserved eggs or embryos suggest a possible ventral brood care. The presence of Kunmingella in coprolites and its numerical abundance in Chengjiang sediment indicate that bradoriids constituted an important source of food for larger predators. Kunmingella differs markedly from the representatives of the crown group Crustacea (extant and Cambrian taxa) and from the stem group derivatives of Crustacea (exemplified by phosphatocopids and some ‘Orsten’ taxa) in showing no major sign of limb specialization (e.g. related to feeding strategies). Although it resembles other Chengjiang euarthropods in important aspects of its body plan (e.g. uniramous antennae, endopod/exopod configuration), Kunmingella possesses several features (e.g. antennal morphology, post-antennular appendages with 5-segmented endopods) which support the view that bradoriids may be very early derivatives of the stem line Crustacea.",
    url = "https://doi.org/10.1111/j.1502-3931.1999.tb00547.x",
    doi = "10.1111/j.1502-3931.1999.tb00547.x",
    openalex = "W1989069995",
    references = "briggs1994decay, doi101016003101827190040x, doi101017s002233600002758x, doi101098rstb19910094, doi101144gsjgs15061035, doi101163193724087x00054, doi101826182003741571989, doi101826182003769311997, doi1023073515467, doi105962bhltitle41372, openalexw2134978213, openalexw2754161204, xianguang1999new"
}

Trying to review the Cambrian diversity of Crustacea, it became necessary to first characterize the Crustacea as a monophylum with a reconstruction of the ground pattern and autapomorphies of its stem species. Some of the major evolutionary developments toward the crown group, Eucrustacea, are also illuminated. The view presented is founded largely on minute three-dimensional, phosphatized fossils from the Swedish ‘Orsten’, a special type of bituminous Cambrian limestone rock, which have been studied since about 15 years now in co-operation with the discoverer of the ‘Orsten’ material, Klaus Müller from Bonn. With respect to the lowermost Cambrian record of the Phosphatocopina, the possible sister group of Eucrustacea and most abundant in the ‘Orsten’ material, it seems evident that Crustacea must have developed well before the Cambrian and had diversified into all major descendent lines before the end of this time period. The missing record, particularly of the Malacostraca (those records noted so far can be clearly falsified) is interpreted as simply due to the small preservational window we have into the Cambrian world so far. In fact, there are only two major sources: the flat fossils in the millimetre to centimetre range from Lower to Upper Middle Cambrian Burgess Shale type of localities, and the minute 3D-preserved fossils from Lower to Upper Cambrian ‘Orsten’ localities. The evident origin of the Crustacea well down in the Pre-Cambrian is, in my view, a further challenge to the idea of a “Cambrian explosion”.

@incollection{doi1011639789004630543003,
    author = "Waloßek, Dieter",
    title = "On the Cambrian Diversity of Crustacea",
    year = "1999",
    abstract = "Trying to review the Cambrian diversity of Crustacea, it became necessary to first characterize the Crustacea as a monophylum with a reconstruction of the ground pattern and autapomorphies of its stem species. Some of the major evolutionary developments toward the crown group, Eucrustacea, are also illuminated. The view presented is founded largely on minute three-dimensional, phosphatized fossils from the Swedish ‘Orsten’, a special type of bituminous Cambrian limestone rock, which have been studied since about 15 years now in co-operation with the discoverer of the ‘Orsten’ material, Klaus Müller from Bonn. With respect to the lowermost Cambrian record of the Phosphatocopina, the possible sister group of Eucrustacea and most abundant in the ‘Orsten’ material, it seems evident that Crustacea must have developed well before the Cambrian and had diversified into all major descendent lines before the end of this time period. The missing record, particularly of the Malacostraca (those records noted so far can be clearly falsified) is interpreted as simply due to the small preservational window we have into the Cambrian world so far. In fact, there are only two major sources: the flat fossils in the millimetre to centimetre range from Lower to Upper Middle Cambrian Burgess Shale type of localities, and the minute 3D-preserved fossils from Lower to Upper Cambrian ‘Orsten’ localities. The evident origin of the Crustacea well down in the Pre-Cambrian is, in my view, a further challenge to the idea of a “Cambrian explosion”.",
    url = "https://doi.org/10.1163/9789004630543\_003",
    doi = "10.1163/9789004630543\_003",
    openalex = "W4383481311"
}

The Cambrian radiation is one of the most exciting and controversial events in the fossil record. It was marked by a sudden abundance of shells, the first steep rise in plots of diversity through time, and the appearance of the fabulous soft‐bodied fossils of the Burgess Shale in British Columbia and elsewhere in the world. The Cambrian radiation was also the subject of Steve Gould's Wonderful Life and Simon Conway Morris's Crucible of Creation.. The Ecology of the Cambrian Radiation is a long‐awaited compilation that tackles one of the more impenetrable parts of the story. Interpretations of ecology are, after all, characteristically equivocal in rocks of this age.

@article{doi101029eo082i024p0026802,
    author = "Briggs, Derek E. G.",
    title = "The Ecology of the Cambrian Radiation",
    year = "2001",
    journal = "Eos",
    abstract = "The Cambrian radiation is one of the most exciting and controversial events in the fossil record. It was marked by a sudden abundance of shells, the first steep rise in plots of diversity through time, and the appearance of the fabulous soft‐bodied fossils of the Burgess Shale in British Columbia and elsewhere in the world. The Cambrian radiation was also the subject of Steve Gould's Wonderful Life and Simon Conway Morris's Crucible of Creation.. The Ecology of the Cambrian Radiation is a long‐awaited compilation that tackles one of the more impenetrable parts of the story. Interpretations of ecology are, after all, characteristically equivocal in rocks of this age.",
    url = "https://doi.org/10.1029/eo082i024p00268-02",
    doi = "10.1029/eo082i024p00268-02",
    openalex = "W1619317983"
}

A new bivalved arthropod is described from the Lower Cambrian (?Upper Atdabanian) Buen Formation of North Greenland. Pauloterminus spinodorsalis gen. et sp. nov. possesses a bivalved carapace that covers the head, which has a single pair of antennae, and anteriormost thorax. No mouthparts are visible. The five‐segmented abdomen was limbless and terminated in a telson plus a pair of large, lobate uropods. A suite of at least six biramous thoracic limbs are present: the short endopods are made up of small, serial podomeres, while the exopods are lobate and may have functioned as gills as well as in swimming. Partially infilled guts are occasionally visible, suggesting that this animal may have been a sediment feeder. It is compared to other Cambrian bivalved arthropods, especially the waptiids Chuandianella ovata from the Lower Cambrian Chengjiang fauna (China) and Waptia fieldensis from the Middle Cambrian Burgess Shale (British Columbia). Of these three animals, the Greenland and Chinese taxa appear to be the most closely related. P. spinodorsalis possesses many typical arthropod features, but it also demonstrates more primitive characters that are more reminiscent of the lobopodians.

@article{doi1011111475498300229,
    author = "Taylor, Rod S.",
    title = "A New Bivalved Arthropod from the Early Cambrian Sirius Passet Fauna, North Greenland",
    year = "2002",
    journal = "Palaeontology",
    abstract = "A new bivalved arthropod is described from the Lower Cambrian (?Upper Atdabanian) Buen Formation of North Greenland. Pauloterminus spinodorsalis gen. et sp. nov. possesses a bivalved carapace that covers the head, which has a single pair of antennae, and anteriormost thorax. No mouthparts are visible. The five‐segmented abdomen was limbless and terminated in a telson plus a pair of large, lobate uropods. A suite of at least six biramous thoracic limbs are present: the short endopods are made up of small, serial podomeres, while the exopods are lobate and may have functioned as gills as well as in swimming. Partially infilled guts are occasionally visible, suggesting that this animal may have been a sediment feeder. It is compared to other Cambrian bivalved arthropods, especially the waptiids Chuandianella ovata from the Lower Cambrian Chengjiang fauna (China) and Waptia fieldensis from the Middle Cambrian Burgess Shale (British Columbia). Of these three animals, the Greenland and Chinese taxa appear to be the most closely related. P. spinodorsalis possesses many typical arthropod features, but it also demonstrates more primitive characters that are more reminiscent of the lobopodians.",
    url = "https://doi.org/10.1111/1475-4983.00229",
    doi = "10.1111/1475-4983.00229",
    openalex = "W1964895651"
}

The shell structure of the Lower Cambrian Mickwitzia, a bilaterally symmetrical bivalve hitherto doubtfully assigned to the Brachiopoda, confirms that the genus shares characters with linguliform brachiopods. The columnar lamination of its organophosphatic shell is homologous with that characterizing acrotretides. The shell, however, is also pervaded by striated apatitic tubes indistinguishable from those permeating the sclerites of the problematic organophosphatic, laminar–shelled Micrina which is close to Halkieria. No crown group brachiopods have such tubes that are presumed to have contained setae. The presence of both these features in the Mickwitzia shell suggests that the stock is a stem group brachiopod with a halkieriid ancestry.

@article{doi1011111475498300265,
    author = "Holmer, Lars E. and Skovsted, Christian B. and Williams, Alwyn",
    title = "A Stem Group Brachiopod From The Lower Cambrian: Support For A Micrina (Halkieriid) Ancestry",
    year = "2002",
    journal = "Palaeontology",
    abstract = "The shell structure of the Lower Cambrian Mickwitzia, a bilaterally symmetrical bivalve hitherto doubtfully assigned to the Brachiopoda, confirms that the genus shares characters with linguliform brachiopods. The columnar lamination of its organophosphatic shell is homologous with that characterizing acrotretides. The shell, however, is also pervaded by striated apatitic tubes indistinguishable from those permeating the sclerites of the problematic organophosphatic, laminar–shelled Micrina which is close to Halkieria. No crown group brachiopods have such tubes that are presumed to have contained setae. The presence of both these features in the Mickwitzia shell suggests that the stock is a stem group brachiopod with a halkieriid ancestry.",
    url = "https://doi.org/10.1111/1475-4983.00265",
    doi = "10.1111/1475-4983.00265",
    openalex = "W2080950328"
}

The Burgess Shale arthropod Leanchoilia superlata Walcott 1912, commonly preserves a three-dimensional axial structure generally interpreted as gut contents. Thin-section examination shows this instead to be phosphatized biserially repeated midgut glands, including exceptional preservation of subcellular features. The preferential mineralization of these structures is related to their unusually high chemical reactivity and probably to an internal source of phosphate. Sub-millimetric lineations previously interpreted as annular musculature are in fact planar, sometimes radially arranged, subdivisions of these glands. Ventral rows of isolated phosphate patches appear to represent the same tissue. In extant arthropods, extensively developed midgut glands are related to a rich but infrequent diet with a primary function in storage. Their conspicuous occurrence in unambiguous fossil predators such as Sidneyia and Laggania (Anomalocaris) suggests they served a similar role in the Cambrian; by extension, their conspicuous occurrence in Leanchoilia suggests it was a predator or scavenger. Phosphatized midguts with a structure essentially indistinguishable from that of Leanchoilia are also found in Burgess Shale Odaraia, Canadaspis, Perspicaris, Sidneyia, Anomalocaris, and Opabinia. All are characterized by a distinctive sub-millimetric arrangement of planar elements that is not found in extant arthropods or trilobites, suggesting they diverged before the last common ancestor of extant forms; i.e., they represent stem-group arthropods. Three-dimensionally preserved guts are widely preserved in the Lower Cambrian Chengjiang biota but, unlike those in the Burgess Shale, appear to be filled with sediment. Although generally interpreted as evidence of deposit feeding, the form of these structures points to early permineralization of (sediment-free) midgut glands that were subsequently altered to clay minerals. There is no evidence of deposit feeding in the Chengjiang; indeed, there is a case to be made for deposit feeding not being generally exploited generally until after the Cambrian. Fossils with three-dimensionally preserved axes from the Lower Cambrian Sirius Passet biota have been interpreted as lobopodians; however, most of the putative lobopodian features find alternative interpretations as aspects of Leanchoilia -type midgut glands. Although Kerygmachela is reliably identified as a stem-group arthropod, its phylogenetic position remains unresolved owing to the non-preservation of critical external features and to the plesiomorphic nature of its Leanchoilia -type midgut.

@article{doi1016660094837320020280155lgatio20co2,
    author = "Butterfield, Nicholas J.",
    title = "Leanchoilia guts and the interpretation of three-dimensional structures in Burgess Shale-type fossils",
    year = "2002",
    journal = "Paleobiology",
    abstract = "The Burgess Shale arthropod Leanchoilia superlata Walcott 1912, commonly preserves a three-dimensional axial structure generally interpreted as gut contents. Thin-section examination shows this instead to be phosphatized biserially repeated midgut glands, including exceptional preservation of subcellular features. The preferential mineralization of these structures is related to their unusually high chemical reactivity and probably to an internal source of phosphate. Sub-millimetric lineations previously interpreted as annular musculature are in fact planar, sometimes radially arranged, subdivisions of these glands. Ventral rows of isolated phosphate patches appear to represent the same tissue. In extant arthropods, extensively developed midgut glands are related to a rich but infrequent diet with a primary function in storage. Their conspicuous occurrence in unambiguous fossil predators such as Sidneyia and Laggania (Anomalocaris) suggests they served a similar role in the Cambrian; by extension, their conspicuous occurrence in Leanchoilia suggests it was a predator or scavenger. Phosphatized midguts with a structure essentially indistinguishable from that of Leanchoilia are also found in Burgess Shale Odaraia, Canadaspis, Perspicaris, Sidneyia, Anomalocaris, and Opabinia. All are characterized by a distinctive sub-millimetric arrangement of planar elements that is not found in extant arthropods or trilobites, suggesting they diverged before the last common ancestor of extant forms; i.e., they represent stem-group arthropods. Three-dimensionally preserved guts are widely preserved in the Lower Cambrian Chengjiang biota but, unlike those in the Burgess Shale, appear to be filled with sediment. Although generally interpreted as evidence of deposit feeding, the form of these structures points to early permineralization of (sediment-free) midgut glands that were subsequently altered to clay minerals. There is no evidence of deposit feeding in the Chengjiang; indeed, there is a case to be made for deposit feeding not being generally exploited generally until after the Cambrian. Fossils with three-dimensionally preserved axes from the Lower Cambrian Sirius Passet biota have been interpreted as lobopodians; however, most of the putative lobopodian features find alternative interpretations as aspects of Leanchoilia -type midgut glands. Although Kerygmachela is reliably identified as a stem-group arthropod, its phylogenetic position remains unresolved owing to the non-preservation of critical external features and to the plesiomorphic nature of its Leanchoilia -type midgut.",
    url = "https://doi.org/10.1666/0094-8373(2002)028<0155:lgatio>2.0.co;2",
    doi = "10.1666/0094-8373(2002)028<0155:lgatio>2.0.co;2",
    openalex = "W2175470899",
    references = "doi1010079789401149044, doi101017s002233600002758x, doi10103708944105154544, doi101038001534a0, doi101038114085a0, doi10103835318, doi10103846965, doi101086284623, doi101086415511, doi101098rstb19750033, doi101098rstb19780005, doi101098rstb19810007, doi101098rstb19810164, doi101098rstb19830020, doi101098rstb19850096, doi101111j150239311995tb01587x, doi101126science28153801173, doi101826182003769311997, doi104095103458, doi105281zenodo15992748, müller1983crustacea, openalexw2242001249, openalexw3127114020, openalexw659399033, xianguang1999new"
}

Black shales of the basal Lower Cambrian Niutitang Formation, southeast China, host a regionally distributed concordant, several centimeter-thick, sulfide layer which displays extreme metal enrichment, i.e., Mo-NiSe-Re-Os-As-Hg-Sb >1,000 times enriched and Ag-Au-Pt-Pd >100 times enriched over bulk continental crust. Mineable portions have about 5.5 wt percent Mo, 3.5 wt percent Ni, and 1 g/t PGE + Au. A six-point 187 Os/ 188 Os versus 187 Re/ 188 Os isochron on molybdenum-nickel ore samples defines an age of 541 ± 16 Ma (2σ) with an initial 187 Os/ 188 Os ratio of 0.78 ± 0.19. This age is in agreement with the depositional age of the black shale host; the initial ratio is close to present-day seawater. The sulfide layer/average seawater metal ratio is on the order of 10 6 to 10 8, about 10 to 100 times higher than that for the black shale host and for average metalliferous black shale. Synsedimentary metal enrichment from seawater under anoxic (sulfate-reducing) conditions appears likely but requires an unusually low sedimentation rate and/or high replenishment rate of fresh seawater to the marine basin. The paleogeographic setting of the Lower Cambrian continental margin of the Yangtze craton indicates local basins controlled by synsedimentary rifting. Stagnant water episodically replenished by upwelling oxidized seawater is thought to be responsible for the formation of the polymetallic sulfide layer and of phosphorite, barite, and sapropelic “stone coal” (combustible black shale) beds.

@article{doi102113gsecongeo9751051,
    author = "Mao, Jingwen and Lehmann, Bernd and Du, Andao and Zhang, Guoliang and Ma, Dongsheng and Wang, Yan and Zeng, Min and Kerrich, R.",
    title = "Re-Os Dating of Polymetallic Ni-Mo-PGE-Au Mineralization in Lower Cambrian Black Shales of South China and Its Geologic Significance",
    year = "2002",
    journal = "Economic Geology",
    abstract = "Black shales of the basal Lower Cambrian Niutitang Formation, southeast China, host a regionally distributed concordant, several centimeter-thick, sulfide layer which displays extreme metal enrichment, i.e., Mo-NiSe-Re-Os-As-Hg-Sb >1,000 times enriched and Ag-Au-Pt-Pd >100 times enriched over bulk continental crust. Mineable portions have about 5.5 wt percent Mo, 3.5 wt percent Ni, and 1 g/t PGE + Au. A six-point 187 Os/ 188 Os versus 187 Re/ 188 Os isochron on molybdenum-nickel ore samples defines an age of 541 ± 16 Ma (2σ) with an initial 187 Os/ 188 Os ratio of 0.78 ± 0.19. This age is in agreement with the depositional age of the black shale host; the initial ratio is close to present-day seawater. The sulfide layer/average seawater metal ratio is on the order of 10 6 to 10 8, about 10 to 100 times higher than that for the black shale host and for average metalliferous black shale. Synsedimentary metal enrichment from seawater under anoxic (sulfate-reducing) conditions appears likely but requires an unusually low sedimentation rate and/or high replenishment rate of fresh seawater to the marine basin. The paleogeographic setting of the Lower Cambrian continental margin of the Yangtze craton indicates local basins controlled by synsedimentary rifting. Stagnant water episodically replenished by upwelling oxidized seawater is thought to be responsible for the formation of the polymetallic sulfide layer and of phosphorite, barite, and sapropelic “stone coal” (combustible black shale) beds.",
    url = "https://doi.org/10.2113/gsecongeo.97.5.1051",
    doi = "10.2113/gsecongeo.97.5.1051",
    openalex = "W2097935007",
    references = "doi101016s0031018201002085, doi101017s0016756800155815"
}

The uniramous ‘great appendages’ of several arthropods from the Early to Middle Cambrian are a characteristic pair of pre-oral limbs, which served for prey capture. It has been assumed that the morphological differences between the ‘great-appendage’ arthropods indicate that raptorial antero-ventral and anteriorly pointing appendages evolved more than once in arthropod phylogeny. One set of Cambrian ‘great-appendage’ arthropods has, however, very similar short antero-ventral appendages with a peduncle of two segments angled against each other (elbowed) and with stout distally or medio-distally directed spines or long flexible flagellate spines on each of the four distal segments. Moreover, the head appendages of all these forms comprise the ‘great appendages’ and three pairs of biramous limbs. To this set of taxa we can add a new form from the Lower Cambrian Maotianshan Shale of southern China, Haikoucaris ercaiensis n. gen. and n. sp. It is known from three specimens, possibly being little abundant in the faunal community. It can be distinguished from all other taxa by the prominence of the proximal claw segment of its ‘great appendages’ and by only three distal spines (one on each of the distal segments). The similarity of the short, spiky ‘great appendages’ of Haikoucaris with the chelicera of the Chelicerata leads us to hypothesize that this particular type of ‘great appendages’ was the actual precursor of the chelicera. Homeobox gene and developmental data recently demonstrated the homology between the antenna of ateloceratans and the antennula of crustaceans on one side and the chelicera of chelicerates on the other. To this we add palaeontological evidence for the homology between the chelicerae of chelicerates and the ‘short great appendages’ of certain Cambrian arthropods, which leads us to hypothesize that the evolutionary path went from the ‘short great appendages’, by progressive compaction, toward the chelicera with only a two-spined chela. The new form from China is regarded as the possible latest offshoot, whereas the other ‘great appendages’ arthropods with similar short grasping limbs were derivatives of the stem lineage of the crown-group Chelicerata. Consequently, the chelicera with a chela with one fixed and one mobile finger is an autapomorphy of the crown group of Chelicerata, whereas a raptorial, but more limb-like antenna, with more distal spine-bearing segments, characterized the ground pattern of Chelicerata. Further taxa having ‘great appendages’, including the large Anomalocarididae, are also discussed in the light of their possible affinities to the Chelicerata and possible monophyly of all of these arthropods with raptorial anterior appendages.

@article{doi10108000241160410004764,
    author = "Chen, Junyuan and Waloszek, Dieter and Maas, Andreas",
    title = "A new ‘great‐appendage’ arthropod from the Lower Cambrian of China and homology of chelicerate chelicerae and raptorial antero‐ventral appendages",
    year = "2004",
    journal = "Lethaia",
    abstract = "The uniramous ‘great appendages’ of several arthropods from the Early to Middle Cambrian are a characteristic pair of pre-oral limbs, which served for prey capture. It has been assumed that the morphological differences between the ‘great-appendage’ arthropods indicate that raptorial antero-ventral and anteriorly pointing appendages evolved more than once in arthropod phylogeny. One set of Cambrian ‘great-appendage’ arthropods has, however, very similar short antero-ventral appendages with a peduncle of two segments angled against each other (elbowed) and with stout distally or medio-distally directed spines or long flexible flagellate spines on each of the four distal segments. Moreover, the head appendages of all these forms comprise the ‘great appendages’ and three pairs of biramous limbs. To this set of taxa we can add a new form from the Lower Cambrian Maotianshan Shale of southern China, Haikoucaris ercaiensis n. gen. and n. sp. It is known from three specimens, possibly being little abundant in the faunal community. It can be distinguished from all other taxa by the prominence of the proximal claw segment of its ‘great appendages’ and by only three distal spines (one on each of the distal segments). The similarity of the short, spiky ‘great appendages’ of Haikoucaris with the chelicera of the Chelicerata leads us to hypothesize that this particular type of ‘great appendages’ was the actual precursor of the chelicera. Homeobox gene and developmental data recently demonstrated the homology between the antenna of ateloceratans and the antennula of crustaceans on one side and the chelicera of chelicerates on the other. To this we add palaeontological evidence for the homology between the chelicerae of chelicerates and the ‘short great appendages’ of certain Cambrian arthropods, which leads us to hypothesize that the evolutionary path went from the ‘short great appendages’, by progressive compaction, toward the chelicera with only a two-spined chela. The new form from China is regarded as the possible latest offshoot, whereas the other ‘great appendages’ arthropods with similar short grasping limbs were derivatives of the stem lineage of the crown-group Chelicerata. Consequently, the chelicera with a chela with one fixed and one mobile finger is an autapomorphy of the crown group of Chelicerata, whereas a raptorial, but more limb-like antenna, with more distal spine-bearing segments, characterized the ground pattern of Chelicerata. Further taxa having ‘great appendages’, including the large Anomalocarididae, are also discussed in the light of their possible affinities to the Chelicerata and possible monophyly of all of these arthropods with raptorial anterior appendages.",
    url = "https://doi.org/10.1080/00241160410004764",
    doi = "10.1080/00241160410004764",
    openalex = "W1763189032",
    references = "doi1010079789401149044, doi101017s002233600002758x, doi101038337695c0, doi101038417271a, doi101046j1525142x200202034x, doi101073pnas951810665, doi101073pnas951810671, doi101098rspb19980385, doi101098rstb19810033, doi1011111475498300244, doi101111j150239311990tb01373x, doi1016660094837320020280155lgatio20co2, doi101826182003769311997, doi104095103458, doi105281zenodo16490103, doi105860choice395182, dzik1988the, openalexw2240758963, xianguang1999new"
}

In this study, we illustrate an exceptionally well-preserved Haikouichthys ercaicunensis from the Lower Cambrian Chengjiang fauna that displays complete single dorsal, ventral and caudal fins. This 530-million-year old vertebrate is fish-shaped and characterized by a single median fin-fold, which is an essential trait of the initial vertebrate chordates. The radially orientated ray-like structures in its dorsal fin somewhat resemble but are probably not real radials seen in basal vertebrates, such as hagfishes and lampreys. The unique design of primitive fins and fin structures provides additional insights into the early evolution of vertebrates.

@article{doi101111j14209101200400741x,
    author = "Zhang, X.-G. and Hou, Xianguang",
    title = "Evidence for a single median fin-fold and tail in the Lower Cambrian vertebrate, Haikouichthys ercaicunensis",
    year = "2004",
    journal = "Journal of Evolutionary Biology",
    abstract = "In this study, we illustrate an exceptionally well-preserved Haikouichthys ercaicunensis from the Lower Cambrian Chengjiang fauna that displays complete single dorsal, ventral and caudal fins. This 530-million-year old vertebrate is fish-shaped and characterized by a single median fin-fold, which is an essential trait of the initial vertebrate chordates. The radially orientated ray-like structures in its dorsal fin somewhat resemble but are probably not real radials seen in basal vertebrates, such as hagfishes and lampreys. The unique design of primitive fins and fin structures provides additional insights into the early evolution of vertebrates.",
    url = "https://doi.org/10.1111/j.1420-9101.2004.00741.x",
    doi = "10.1111/j.1420-9101.2004.00741.x",
    openalex = "W2144594244",
    references = "doi101111j150239311998tb00509x"
}

@article{doi101016jpalaeo200306001,
    author = "Steiner, Michael and Zhu, Maoyan and Zhao, Yuanlong and Erdtmann, Bernd-Dietrich",
    title = "Lower Cambrian Burgess Shale-type fossil associations of South China",
    year = "2005",
    journal = "Palaeogeography Palaeoclimatology Palaeoecology",
    url = "https://doi.org/10.1016/j.palaeo.2003.06.001",
    doi = "10.1016/j.palaeo.2003.06.001",
    openalex = "W2022462295",
    references = "doi101016s0031018201002085, doi101017s002233600002758x, doi101017s0022336000037057, doi101017s0094837300009994, doi10103846965, doi101111j150239311995tb01587x, doi1011300091761319940220179pcbgsr23co2, doi101826182003769311997, doi1018814epiiugs1995v18i12003, doi1023072992562, openalexw1573076930, openalexw3127114020, openalexw650377807, xianguang1999new"
}

The fossil record plays a key role in reconstructing deep evolutionary relationships through its documentation of the early diverging stem groups leading to extant phyla. In the middle Cambrian Burgess Shale, two famously problematic worms, Odontogriphus and Wiwaxia, have recently been reinterpreted as stem-group molluscs based on their shared expression of a putative radula and putative ctenidia in Odontogriphus. More detailed analysis of these fossil structures, however, reveals pronounced anatomical and histological discrepancies with molluscan analogues, such that they are more reliably interpreted as primitive features of the superphylum Lophotrochozoa. In the absence of any obviously derived characters, Odontogriphus could be placed in the stem group of the Lophotrochozoa or on the stem of any of its constituent phyla, whereas the dorsal covering of chaetae in Wiwaxia identifies it as a stem-group polychaete. Despite their close relationship, these two jawed, segmented worms could conceivably represent the early stages of two separate phyla.

@article{doi101002bies20507,
    author = "Butterfield, Nicholas J.",
    title = "Hooking some stem‐group “worms”: fossil lophotrochozoans in the Burgess Shale",
    year = "2006",
    journal = "BioEssays",
    abstract = "The fossil record plays a key role in reconstructing deep evolutionary relationships through its documentation of the early diverging stem groups leading to extant phyla. In the middle Cambrian Burgess Shale, two famously problematic worms, Odontogriphus and Wiwaxia, have recently been reinterpreted as stem-group molluscs based on their shared expression of a putative radula and putative ctenidia in Odontogriphus. More detailed analysis of these fossil structures, however, reveals pronounced anatomical and histological discrepancies with molluscan analogues, such that they are more reliably interpreted as primitive features of the superphylum Lophotrochozoa. In the absence of any obviously derived characters, Odontogriphus could be placed in the stem group of the Lophotrochozoa or on the stem of any of its constituent phyla, whereas the dorsal covering of chaetae in Wiwaxia identifies it as a stem-group polychaete. Despite their close relationship, these two jawed, segmented worms could conceivably represent the early stages of two separate phyla.",
    url = "https://doi.org/10.1002/bies.20507",
    doi = "10.1002/bies.20507",
    openalex = "W1981738126",
    references = "doi101007bf00226666"
}

Abstract A fauna of brachiopods and small shelly fossils from the Lower Cambrian Harkless Formation of Esmeraldina County in southern Nevada is described. The brachiopod Kyrshabaktella sp. provides the first unequivocal record of lingulids in the Lower Cambrian of the Great Basin. The shells of Kyrshabaktella sp. are fragmentary, but otherwise well preserved and an acrotretid-like columnar shell structure is demonstrated. The phosphatic tubular fossil Hyolithellus insolitus is described from North America for the first time and Sphenothallus sp. provides the oldest record of this problematic genus in Laurentian strata. Other faunal elements include two additional linguliform brachiopods, echinoderm ossicles and sponge spicules.

@article{doi10108011035890601284327,
    author = "Skovsted, Christian B. and Holmer, Lars E.",
    title = "The Lower Cambrian brachiopod Kyrshabaktella and associated shelly fossils from the Harkless Formation, southern Nevada",
    year = "2006",
    journal = "GFF",
    abstract = "Abstract A fauna of brachiopods and small shelly fossils from the Lower Cambrian Harkless Formation of Esmeraldina County in southern Nevada is described. The brachiopod Kyrshabaktella sp. provides the first unequivocal record of lingulids in the Lower Cambrian of the Great Basin. The shells of Kyrshabaktella sp. are fragmentary, but otherwise well preserved and an acrotretid-like columnar shell structure is demonstrated. The phosphatic tubular fossil Hyolithellus insolitus is described from North America for the first time and Sphenothallus sp. provides the oldest record of this problematic genus in Laurentian strata. Other faunal elements include two additional linguliform brachiopods, echinoderm ossicles and sponge spicules.",
    url = "https://doi.org/10.1080/11035890601284327",
    doi = "10.1080/11035890601284327",
    openalex = "W2055796612",
    references = "doi101080037454809494387, doi101080037454809496570, doi103133pp483f, doi105479si009638011395227, doi105962bhltitle13172, doi105962bhltitle13182"
}

Abstract A new genus and species of a Middle Cambrian stem group brachiopod, Acanthotretella spinosa n. gen. and n. sp., is described from the Burgess Shale Formation. Most of the 42 specimens studied came from the Greater Phyllopod bed (Walcott Quarry) and were collected from five bed assemblages, each representing a single obrution event. Specimens are probably preserved within their original habitat. In contrast to all brachiopods known from the Burgess Shale, the shells of the new stem group brachiopod are often deformed and do not show signs of brittle breakage, which suggests that the valves were originally either entirely organic in composition or, more likely, had just a minor mineral component. Acanthotretella spinosa differs from all the other described Cambrian brachiopods in that it is covered by long, slender and possibly partly mineralized spines that are posteriorly inclined at an oblique angle away from the anterior margin. The spines penetrate the shell and are mainly comparable with the thorn‐like organic objects that have been inferred from early siphonotretoid brachiopods. The pedicle was slender and was composed of a central coelomic region and emerged from an apical foramen at the end of an internal pedicle tube. The finding of a pedicle attached to the macrobenthic algae Dictyophycus and other epibenthos implies that A. spinosa did not have an infaunal mode of life. The visceral region and interior characters are poorly preserved.

@article{doi101111j14636395200600241x,
    author = "Holmer, Lars E. and Caron, Jean‐Bernard",
    title = "A spinose stem group brachiopod with pedicle from the Middle Cambrian Burgess Shale",
    year = "2006",
    journal = "Acta Zoologica",
    abstract = "Abstract A new genus and species of a Middle Cambrian stem group brachiopod, Acanthotretella spinosa n. gen. and n. sp., is described from the Burgess Shale Formation. Most of the 42 specimens studied came from the Greater Phyllopod bed (Walcott Quarry) and were collected from five bed assemblages, each representing a single obrution event. Specimens are probably preserved within their original habitat. In contrast to all brachiopods known from the Burgess Shale, the shells of the new stem group brachiopod are often deformed and do not show signs of brittle breakage, which suggests that the valves were originally either entirely organic in composition or, more likely, had just a minor mineral component. Acanthotretella spinosa differs from all the other described Cambrian brachiopods in that it is covered by long, slender and possibly partly mineralized spines that are posteriorly inclined at an oblique angle away from the anterior margin. The spines penetrate the shell and are mainly comparable with the thorn‐like organic objects that have been inferred from early siphonotretoid brachiopods. The pedicle was slender and was composed of a central coelomic region and emerged from an apical foramen at the end of an internal pedicle tube. The finding of a pedicle attached to the macrobenthic algae Dictyophycus and other epibenthos implies that A. spinosa did not have an infaunal mode of life. The visceral region and interior characters are poorly preserved.",
    url = "https://doi.org/10.1111/j.1463-6395.2006.00241.x",
    doi = "10.1111/j.1463-6395.2006.00241.x",
    openalex = "W2156029888",
    references = "doi101111j14636395200500211x, doi105962bhltitle14915"
}

The remarkable brachiopod Xianshanella haikouensis, from the Early Cambrian Chengjiang Lagerstätte, was briefly reported based on only two extraordinarily preserved specimens. Details of valve interiors remain unknown due to a lack of available material. We herein reillustrate the holotype of X. haikouensis, and, on the basis of many additional specimens from the type locality, provide further information on this brachiopod taxon, including shell ornamentation, a U-shaped digestive tract, mantle canal systems, lophophores, muscle scars, and well-defined visceral areas in the valves. This exceptional brachiopod is characterized by a biconvex, rounded, knob-shaped shell lacking visible pseudointerarea in the valves, an elongate and muscular pedicle, and, especially, its possession of exceptional setal fringes. A restudy of a number of new specimens justifies assigning Xianshanella to the family Obolidae. The elongate and horny setae of X. haikouensis, coupled with the massive pedicle in many cases with its end attached to shells of other animals, indicate that this species was an epibenthic, sessile suspension feeder, attached by a pedicle.

@article{doi1016660022336020060800203ndotrc20co2,
    author = "Zhang, Zhifei and Shu, Degan and Han, Jian and Liu, Jianni",
    title = "NEW DATA ON THE RARE CHENGJIANG (LOWER CAMBRIAN, SOUTH CHINA) LINGULOID BRACHIOPOD XIANSHANELLA HAIKOUENSIS",
    year = "2006",
    journal = "Journal of Paleontology",
    abstract = "The remarkable brachiopod Xianshanella haikouensis, from the Early Cambrian Chengjiang Lagerstätte, was briefly reported based on only two extraordinarily preserved specimens. Details of valve interiors remain unknown due to a lack of available material. We herein reillustrate the holotype of X. haikouensis, and, on the basis of many additional specimens from the type locality, provide further information on this brachiopod taxon, including shell ornamentation, a U-shaped digestive tract, mantle canal systems, lophophores, muscle scars, and well-defined visceral areas in the valves. This exceptional brachiopod is characterized by a biconvex, rounded, knob-shaped shell lacking visible pseudointerarea in the valves, an elongate and muscular pedicle, and, especially, its possession of exceptional setal fringes. A restudy of a number of new specimens justifies assigning Xianshanella to the family Obolidae. The elongate and horny setae of X. haikouensis, coupled with the massive pedicle in many cases with its end attached to shells of other animals, indicate that this species was an epibenthic, sessile suspension feeder, attached by a pedicle.",
    url = "https://doi.org/10.1666/0022-3360(2006)080[0203:ndotrc]2.0.co;2",
    doi = "10.1666/0022-3360(2006)080[0203:ndotrc]2.0.co;2",
    openalex = "W2175497786",
    references = "doi10108000222935608697572, doi101080037454809494387, doi101080037454809496570"
}

Abstract The degree to which the original community composition of the Middle Cambrian Burgess Shale was altered through transport and decay and how taphonomic conditions varied through time and across taxa is poorly understood. To address these issues, variation in fossil preservation was analyzed through a vertical succession of 26 bed assemblages, each representing a single obrution event, within the 7-m-thick Greater Phyllopod Bed of the Walcott Quarry. More than 50,000 specimens belonging to 158 genera—mostly benthic, monospecific and nonbiomineralized—were included in this analysis. The decay gradient of the polychaete Burgessochaeta setigera was used as a taphonomic threshold to estimate how far decay had proceeded in each bed assemblage. Qualitative comparisons of the degree of preservation of 15 species, representing an array of different body plans, demonstrate that all bed assemblages contain a mix of articulated and in situ dissociated or completely dissociated organisms interpreted respectively as census- and time-averaged assemblages. Furthermore: (1) most organisms studied were preserved within their habitat and only slightly disturbed during burial; (2) most decay processes took place prior to burial and resulted in disarticulation of organisms at the time of burial; (3) the degree of disarticulation was variable within individuals of the same population and between populations; and (4) early mineralization of tissues across all body plans occurred soon after burial. Canonical correspondence analysis summarizes the apparent variations in the amount of preburial decay, or time averaging, across species, individuals, and bed assemblages. The effect of time averaging, however, must have been limited because rarefaction curves reveal no link between decay and species richness. This suggests that decay is not an important community controlling factor. Overall, our data suggest that transport was trivial and the traditional distinction between a pre- and postslide environment is unnecessary. It is likely that all specimens present at the time of burial would have been preserved independent of their original tissue composition and degree of preburial decay. The presence of extensive sheets of Morania confluens, a putative benthic cyanobacterium, in most bed assemblages suggests that it: (1) provided a stable substrate and food source for a number of benthic metazoans, and (2) played a possible role in the preservation of nonbiomineralized animals, acting as a barrier in maintaining local anoxic pore-water conditions.

@article{doi102110palo2003p05070r,
    author = "Caron, Jean‐Bernard and Jackson, Donald A.",
    title = "TAPHONOMY OF THE GREATER PHYLLOPOD BED COMMUNITY, BURGESS SHALE",
    year = "2006",
    journal = "Palaios",
    abstract = "Abstract The degree to which the original community composition of the Middle Cambrian Burgess Shale was altered through transport and decay and how taphonomic conditions varied through time and across taxa is poorly understood. To address these issues, variation in fossil preservation was analyzed through a vertical succession of 26 bed assemblages, each representing a single obrution event, within the 7-m-thick Greater Phyllopod Bed of the Walcott Quarry. More than 50,000 specimens belonging to 158 genera—mostly benthic, monospecific and nonbiomineralized—were included in this analysis. The decay gradient of the polychaete Burgessochaeta setigera was used as a taphonomic threshold to estimate how far decay had proceeded in each bed assemblage. Qualitative comparisons of the degree of preservation of 15 species, representing an array of different body plans, demonstrate that all bed assemblages contain a mix of articulated and in situ dissociated or completely dissociated organisms interpreted respectively as census- and time-averaged assemblages. Furthermore: (1) most organisms studied were preserved within their habitat and only slightly disturbed during burial; (2) most decay processes took place prior to burial and resulted in disarticulation of organisms at the time of burial; (3) the degree of disarticulation was variable within individuals of the same population and between populations; and (4) early mineralization of tissues across all body plans occurred soon after burial. Canonical correspondence analysis summarizes the apparent variations in the amount of preburial decay, or time averaging, across species, individuals, and bed assemblages. The effect of time averaging, however, must have been limited because rarefaction curves reveal no link between decay and species richness. This suggests that decay is not an important community controlling factor. Overall, our data suggest that transport was trivial and the traditional distinction between a pre- and postslide environment is unnecessary. It is likely that all specimens present at the time of burial would have been preserved independent of their original tissue composition and degree of preburial decay. The presence of extensive sheets of Morania confluens, a putative benthic cyanobacterium, in most bed assemblages suggests that it: (1) provided a stable substrate and food source for a number of benthic metazoans, and (2) played a possible role in the preservation of nonbiomineralized animals, acting as a barrier in maintaining local anoxic pore-water conditions.",
    url = "https://doi.org/10.2110/palo.2003.p05-070r",
    doi = "10.2110/palo.2003.p05-070r",
    openalex = "W2112215208",
    references = "doi101016jpalaeo200303001, doi101017cbo9780511623332, doi101038114085a0, doi101038scientificamerican0779122, doi101086282541, doi101098rstb19810164, doi1011300091761319950231079isbapo23co2, doi1023071934145, doi1023071938672, doi1023071940179, doi105860choice273873, openalexw1579996152, openalexw1587627133, openalexw2764433274"
}

Author: Lehmann, B. et al.; Genre: Journal Article; Finally published: 2007; Keywords: Cambrian, black shale, anoxic environments, molybdenum isotopes, China; Title: Highly metalliferous carbonaceous shale and Early Cambrian seawater

@article{doi101130g23543a1,
    author = "Lehmann, Bernd and Nägler, Thomas F. and Holland, Heinrich and Wille, Martin and Mao, Jingwen and Pan, Jiayong and Ma, Dongsheng and Dulski, Peter",
    title = "Highly metalliferous carbonaceous shale and Early Cambrian seawater",
    year = "2007",
    journal = "Geology",
    abstract = "Author: Lehmann, B. et al.; Genre: Journal Article; Finally published: 2007; Keywords: Cambrian, black shale, anoxic environments, molybdenum isotopes, China; Title: Highly metalliferous carbonaceous shale and Early Cambrian seawater",
    url = "https://doi.org/10.1130/g23543a.1",
    doi = "10.1130/g23543a.1",
    openalex = "W2148077486",
    references = "doi101016s0031018201002085"
}

Naraoiids, defined as lightly sclerotized arthropods with a dimidiate tergum of two sclerites separated by a single transverse articulation, have been found in the Cambrian and Silurian. During the Cambrian they had a wide distribution coinciding with trilobite realms. This pattern may be related to the breakup of a Neoproterozoic supercontinent, probably Pannotia, which implies that naraoiids originated before the Cambrian “explosion.” Based on new observations on the original material from the Burgess Shale (Middle Cambrian, British Columbia), Naraoia halia is reconsidered as a valid species. The validity is further confirmed by a new record of the occurrence of this species in the Chengjiang Lagerstätte (Lower Cambrian, China). In addition, some structures of N. compacta of the Burgess Shale have been reinterpreted. Two more naraoiid species are redescribed in detail from the Chengjiang Lagerstätte on the basis of more than 1,000 well-preserved specimens. Naraoia spinosa shows dimorphism and Misszhouia longicaudata exhibits geographical variation in the overall shape of the dorsal exoskeleton. Naraoiids may have a protaspis-like larva, but the previously assigned protaspis has proven to be a separate taxon, Primicaris. In dorsal view, naraoiids resemble a giant “degree 0” meraspis (i.e., without thorax), and could have originated from different heterochronic processes, neoteny or hypermorphosis. Naraoiids are generally accepted as vagrant benthos. A predatory/scavenging life mode is supported by functional morphology and recent analogues. A healed injury in M. longicaudata suggests that they could be the prey of larger predators, most likely anomalocaridids. We suggest that differences in exopod composition might represent evolutionary changes through the Early–Middle Cambrian. The monophyly of the Naraoiidae is not firmly established. Similarity to liwiids, supposed to be the close relatives of naraoiids, is limited to overall shape. We exclude naraoiids from the Trilobita, though there do exist a number of similarities between them.

@article{doi101666060821,
    author = "Zhang, X.-L. and Shu, Degan and Erwin, Douglas H.",
    title = "Cambrian Naraoiids (Arthropoda): Morphology, Ontogeny, Systematics, and Evolutionary Relationships",
    year = "2007",
    journal = "Journal of Paleontology",
    abstract = "Naraoiids, defined as lightly sclerotized arthropods with a dimidiate tergum of two sclerites separated by a single transverse articulation, have been found in the Cambrian and Silurian. During the Cambrian they had a wide distribution coinciding with trilobite realms. This pattern may be related to the breakup of a Neoproterozoic supercontinent, probably Pannotia, which implies that naraoiids originated before the Cambrian “explosion.” Based on new observations on the original material from the Burgess Shale (Middle Cambrian, British Columbia), Naraoia halia is reconsidered as a valid species. The validity is further confirmed by a new record of the occurrence of this species in the Chengjiang Lagerstätte (Lower Cambrian, China). In addition, some structures of N. compacta of the Burgess Shale have been reinterpreted. Two more naraoiid species are redescribed in detail from the Chengjiang Lagerstätte on the basis of more than 1,000 well-preserved specimens. Naraoia spinosa shows dimorphism and Misszhouia longicaudata exhibits geographical variation in the overall shape of the dorsal exoskeleton. Naraoiids may have a protaspis-like larva, but the previously assigned protaspis has proven to be a separate taxon, Primicaris. In dorsal view, naraoiids resemble a giant “degree 0” meraspis (i.e., without thorax), and could have originated from different heterochronic processes, neoteny or hypermorphosis. Naraoiids are generally accepted as vagrant benthos. A predatory/scavenging life mode is supported by functional morphology and recent analogues. A healed injury in M. longicaudata suggests that they could be the prey of larger predators, most likely anomalocaridids. We suggest that differences in exopod composition might represent evolutionary changes through the Early–Middle Cambrian. The monophyly of the Naraoiidae is not firmly established. Similarity to liwiids, supposed to be the close relatives of naraoiids, is limited to overall shape. We exclude naraoiids from the Trilobita, though there do exist a number of similarities between them.",
    url = "https://doi.org/10.1666/06-082.1",
    doi = "10.1666/06-082.1",
    openalex = "W2173000958",
    references = "doi101017s000632310000548x, doi101017s000632319800512x, doi1011300016760619971090016onpgat23co2, doi1011300091761319950230407scirpo23co2, doi1015159780691207278, doi105860choice273873, doi105860choice341536, doi105962bhltitle156765, doi107208chicago97802262565730010001, openalexw1497041718"
}

The morphology of Tuzoia is reinterpreted in the light of abundant new specimens from the Middle Cambrian Burgess Shale (British Columbia, Canada) and Kaili (Guizhou, China) Lagerstätten. Tuzoia was a very large (up to 180 mm long) bivalved arthropod with a nonmineralized domelike carapace strengthened by prominent pointed features and often flanked by a lateral ridge bearing a spiny frill. The reticulate pattern of Tuzoia is comparable with that of present-day crustaceans (e.g., myodocope ostracods) and is interpreted as a structural compromise between exoskeletal lightness and high resistance to mechanical stress. Tuzoia had a pair of large, stalked, spherical, possibly compound eyes facing forward. Flagella-like antennae protruded through the anterior notch. No other appendages are known except possible filamentous setae underlying the carapace. Tuzoia typically occurs as laterally (lc) or dorsoventrally (dvc) compacted carapaces or single valves. Each type (lc or dvc) emphasizes particular aspects of the morphology (e.g., spiny lateral ridge, ventral margin) that were often interpreted as specific differences by previous authors. A revision of Tuzoia validates only 7 of the 23 named species. Tuzoia is placed tentatively within a group of large bivalved arthropods along with Isoxys and the possible ancestors of Thylacocephala (Lower Cambrian–Upper Cretaceous). In the Middle Cambrian, Tuzoia occurs across Laurentia, South and North China, and the Perigondwanan area (Bohemia) within a relatively narrow subtropical belt, indicating a high dispersal capability and possible latitudinal control on its distribution. Functional morphology, taphonomy, and the distributional pattern indicate that Tuzoia was a free-swimming arthropod.

@article{doi101666pleo050701,
    author = "Vannier, Jean and Caron, Jean‐Bernard and Yuan, Jinliang and Briggs, Derek E. G. and Collins, Desmond and Zhao, Yuanlong and Zhu, Maoyan",
    title = "TUZOIA: MORPHOLOGY AND LIFESTYLE OF A LARGE BIVALVED ARTHROPOD OF THE CAMBRIAN SEAS",
    year = "2007",
    journal = "Journal of Paleontology",
    abstract = "The morphology of Tuzoia is reinterpreted in the light of abundant new specimens from the Middle Cambrian Burgess Shale (British Columbia, Canada) and Kaili (Guizhou, China) Lagerstätten. Tuzoia was a very large (up to 180 mm long) bivalved arthropod with a nonmineralized domelike carapace strengthened by prominent pointed features and often flanked by a lateral ridge bearing a spiny frill. The reticulate pattern of Tuzoia is comparable with that of present-day crustaceans (e.g., myodocope ostracods) and is interpreted as a structural compromise between exoskeletal lightness and high resistance to mechanical stress. Tuzoia had a pair of large, stalked, spherical, possibly compound eyes facing forward. Flagella-like antennae protruded through the anterior notch. No other appendages are known except possible filamentous setae underlying the carapace. Tuzoia typically occurs as laterally (lc) or dorsoventrally (dvc) compacted carapaces or single valves. Each type (lc or dvc) emphasizes particular aspects of the morphology (e.g., spiny lateral ridge, ventral margin) that were often interpreted as specific differences by previous authors. A revision of Tuzoia validates only 7 of the 23 named species. Tuzoia is placed tentatively within a group of large bivalved arthropods along with Isoxys and the possible ancestors of Thylacocephala (Lower Cambrian–Upper Cretaceous). In the Middle Cambrian, Tuzoia occurs across Laurentia, South and North China, and the Perigondwanan area (Bohemia) within a relatively narrow subtropical belt, indicating a high dispersal capability and possible latitudinal control on its distribution. Functional morphology, taphonomy, and the distributional pattern indicate that Tuzoia was a free-swimming arthropod.",
    url = "https://doi.org/10.1666/pleo05070.1",
    doi = "10.1666/pleo05070.1",
    openalex = "W2176042563",
    references = "doi101016s0031018203003006, doi101016s0031018203003079, doi101038114085a0, doi10103835106514, doi101130gsab49195, doi1016660094837320020280155lgatio20co2, doi101826182003769311997, doi102110palo2003p05070r, doi105962bhltitle7419, openalexw1573076930, openalexw2754161204"
}

@incollection{crossref2008cambrian,
    title = "Cambrian",
    year = "2008",
    booktitle = "Encyclopedia of Genetics, Genomics, Proteomics and Informatics",
    url = "https://doi.org/10.1007/978-1-4020-6754-9\_2226",
    doi = "10.1007/978-1-4020-6754-9\_2226",
    pages = "255-255"
}

Although Cambrian Burgess Shale–type (BST) biotas are fundamental to understanding the radiation of metazoans, the nature of their extraordinary preservation remains controversial. There remains disagreement about the importance of the role of early mineral replication of soft tissues versus the conservation of primary organic remains. Most prior work focused on soft-bodied fossils from the two most important BST biotas, those of the Burgess Shale (Canada) and Maotianshan Shale (Chengjiang, China). Fossils from these two deposits do not provide ideal candidates for specimen-level taphonomic study because they have been altered: the Burgess Shale by greenschist facies metamorphism and the Maotianshan Shale by intensive subsurface weathering. Elemental mapping of soft-bodied fossils from 11 other BST deposits worldwide demonstrates that BST preservation represents a single major taphonomic pathway that may share a common cause wherever it occurs. The conservation of organic tissues, and not early authigenic mineralization, is the primary mechanism responsible for the preservation of BST assemblages. Early authigenic mineral replacement preserves certain anatomical features of some specimens, but the preservation of non-biomineralized BST fossils requires suppression of the processes that normally lead to the degradation of organic remains in marine environments.

@article{doi101130g24961a1,
    author = "Gaines, Robert R. and Briggs, Derek E. G. and Yuanlong, Zhao",
    title = "Cambrian Burgess Shale–type deposits share a common mode of fossilization",
    year = "2008",
    journal = "Geology",
    abstract = "Although Cambrian Burgess Shale–type (BST) biotas are fundamental to understanding the radiation of metazoans, the nature of their extraordinary preservation remains controversial. There remains disagreement about the importance of the role of early mineral replication of soft tissues versus the conservation of primary organic remains. Most prior work focused on soft-bodied fossils from the two most important BST biotas, those of the Burgess Shale (Canada) and Maotianshan Shale (Chengjiang, China). Fossils from these two deposits do not provide ideal candidates for specimen-level taphonomic study because they have been altered: the Burgess Shale by greenschist facies metamorphism and the Maotianshan Shale by intensive subsurface weathering. Elemental mapping of soft-bodied fossils from 11 other BST deposits worldwide demonstrates that BST preservation represents a single major taphonomic pathway that may share a common cause wherever it occurs. The conservation of organic tissues, and not early authigenic mineralization, is the primary mechanism responsible for the preservation of BST assemblages. Early authigenic mineral replacement preserves certain anatomical features of some specimens, but the preservation of non-biomineralized BST fossils requires suppression of the processes that normally lead to the degradation of organic remains in marine environments.",
    url = "https://doi.org/10.1130/g24961a.1",
    doi = "10.1130/g24961a.1",
    openalex = "W2162666312",
    references = "briggs2003the, doi101016jchemgeo200409003, doi101016jpalaeo200306001, doi101016jpalaeo200407034, doi101017s0094837300009994, doi101038114085a0, doi101093icb431166, doi101098rstb19810007, doi101111j14754983200700656x, doi101111j150239311995tb01587x, doi101126science28153801173, doi101130g206401, doi101139e06012, doi1016660094837320020280155lgatio20co2, doi102517prpsj771, openalexw2527820321, openalexw2912219260, openalexw3127114020"
}

Morris, Simon Conway, Peel, John S. (2008): The earliest annelids: Lower Cambrian polychaetes from the Sirius Passet Lagerstätte, Peary Land, North Greenland. Acta Palaeontologica Polonica 53 (1): 137-148, DOI: 10.4202/app.2008.0110, URL: http://www.app.pan.pl/article/item/app53-137.html

@article{doi104202app20080110,
    author = "Morris, Simon Conway and Peel, John S.",
    title = "The Earliest Annelids: Lower Cambrian Polychaetes from the Sirius Passet Lagerstätte, Peary Land, North Greenland",
    year = "2008",
    journal = "Acta Palaeontologica Polonica",
    abstract = "Morris, Simon Conway, Peel, John S. (2008): The earliest annelids: Lower Cambrian polychaetes from the Sirius Passet Lagerstätte, Peary Land, North Greenland. Acta Palaeontologica Polonica 53 (1): 137-148, DOI: 10.4202/app.2008.0110, URL: http://www.app.pan.pl/article/item/app53-137.html",
    url = "https://doi.org/10.4202/app.2008.0110",
    doi = "10.4202/app.2008.0110",
    openalex = "W2095644294",
    references = "doi101038345802a0, doi10108003115517908565437"
}

Abstract: Abundant material from a new quarry excavated in the lower Cambrian Emu Bay Shale (Kangaroo Island, South Australia) and, particularly, the preservation of soft‐bodied features previously unknown from this Burgess Shale‐type locality, permit the revision of two bivalved arthropod taxa described in the late 1970s, Isoxys communis and Tuzoia australis. The collections have also produced fossils belonging to two new species: Isoxys glaessneri and Tuzoia sp. Among the soft parts preserved in these taxa are stalked eyes, digestive structures and cephalic and trunk appendages, rivalling in quality and quantity those described from better‐known Lagerstätten, notably the lower Cambrian Chengjiang fauna of China and the middle Cambrian Burgess Shale of Canada.

@article{doi101111j14754983200900914x,
    author = "García‐Bellido, Diego C. and Paterson, John R. and Edgecombe, Gregory D. and Jago, J. B. and Gehlîng, James G. and Lee, Michael S. Y.",
    title = "The bivalved arthropods Isoxys and Tuzoia with soft‐part preservation from the Lower Cambrian Emu Bay Shale Lagerstätte (Kangaroo Island, Australia)",
    year = "2009",
    journal = "Palaeontology",
    abstract = "Abstract: Abundant material from a new quarry excavated in the lower Cambrian Emu Bay Shale (Kangaroo Island, South Australia) and, particularly, the preservation of soft‐bodied features previously unknown from this Burgess Shale‐type locality, permit the revision of two bivalved arthropod taxa described in the late 1970s, Isoxys communis and Tuzoia australis. The collections have also produced fossils belonging to two new species: Isoxys glaessneri and Tuzoia sp. Among the soft parts preserved in these taxa are stalked eyes, digestive structures and cephalic and trunk appendages, rivalling in quality and quantity those described from better‐known Lagerstätten, notably the lower Cambrian Chengjiang fauna of China and the middle Cambrian Burgess Shale of Canada.",
    url = "https://doi.org/10.1111/j.1475-4983.2009.00914.x",
    doi = "10.1111/j.1475-4983.2009.00914.x",
    openalex = "W2008588765",
    references = "doi10100797894017363743, doi101016003101829390065q, doi101016jpalwor200610014, doi101080002411600750053862, doi10108003115517908565437, doi101111j14754983200700649x, doi1016660022336020030770674ansftp20co2, doi1016660094837320020280155lgatio20co2, doi101666pleo050701, doi101826182003769311997, doi104202app20080110, doi104202app20090024, doi105860choice416546, doi105962bhltitle14915, openalexw1573076930, openalexw3127114020"
}

Abstract: The lower Cambrian Emu Bay Shale on Kangaroo Island, South Australia, contains the only known Cambrian Burgess Shale‐type biota in Australia. Two new lamellipedian arthropods, Emucaris fava gen. et sp. nov. and Kangacaris zhangi gen. et sp. nov., from the Emu Bay Shale Lagerstätte are described as monotypic genera that are resolved cladistically as a monophyletic group that is sister to Naraoiidae + Liwiidae and classified within the Nektaspida as a new family Emucarididae. Shared derived characters of Emucarididae involve a bipartite, elongate hypostome and elongation of the pygidium relative to the cephalic shield and very short thorax. A monophyletic Liwiidae is composed of Liwia and the Ordovician Tariccoia + Soomaspis but excludes Buenaspis, and even the membership of Buenaspis in Nektaspida is contradicted amongst the shortest cladograms. New morphological interpretations favour affinities of Kwanyinaspis with Conciliterga rather than with Aglaspidida, and Phytophilaspis with Petalopleura.

@article{doi101111j14754983201000932x,
    author = "Paterson, John R. and Edgecombe, Gregory D. and García‐Bellido, Diego C. and Jago, J. B. and Gehlîng, James G.",
    title = "Nektaspid arthropods from the Lower Cambrian Emu Bay Shale Lagerstätte, South Australia, with a reassessment of lamellipedian relationships",
    year = "2010",
    journal = "Palaeontology",
    abstract = "Abstract: The lower Cambrian Emu Bay Shale on Kangaroo Island, South Australia, contains the only known Cambrian Burgess Shale‐type biota in Australia. Two new lamellipedian arthropods, Emucaris fava gen. et sp. nov. and Kangacaris zhangi gen. et sp. nov., from the Emu Bay Shale Lagerstätte are described as monotypic genera that are resolved cladistically as a monophyletic group that is sister to Naraoiidae + Liwiidae and classified within the Nektaspida as a new family Emucarididae. Shared derived characters of Emucarididae involve a bipartite, elongate hypostome and elongation of the pygidium relative to the cephalic shield and very short thorax. A monophyletic Liwiidae is composed of Liwia and the Ordovician Tariccoia + Soomaspis but excludes Buenaspis, and even the membership of Buenaspis in Nektaspida is contradicted amongst the shortest cladograms. New morphological interpretations favour affinities of Kwanyinaspis with Conciliterga rather than with Aglaspidida, and Phytophilaspis with Petalopleura.",
    url = "https://doi.org/10.1111/j.1475-4983.2010.00932.x",
    doi = "10.1111/j.1475-4983.2010.00932.x",
    openalex = "W2152987321",
    references = "doi10108003115510508619300, doi101666060821, doi105962bhltitle14915"
}

Abstract: The complex history of description of the anomalocaridids has partly been caused by the fragmentary nature of these fossils. Frontal appendages and mouth parts are more readily preserved than whole-body assemblages, so the earliest work on these animals examined these structures in isolation. After several decades of research, these disarticulated elements were assembled together to reconstruct the anomalocaridid body plan, and a total of three Burgess Shale genera, Anomalocaris, Laggania and Hurdia, were described in full. Here we present new frontal appendage material of additional anomalocaridid taxa from the 'Middle' Cambrian (Series 3) Burgess Shale Formation in Canada, showing that the diversity of anomalocaridids in this locality is even higher than previously thought. Material includes Amplectobelua stephenensis sp. nov., the first known occurrence of this genus outside of China; Caryosyntrips serratus gen. et sp. nov., which is similar to the Anomalocaris appendage but has a straighter outline and a different arrangement of spines; and an appendage that may be either the Laggania appendage or a third morph of the Hurdia appendage. The new anomalocaridid material is contemporaneous with the previously described taxa Anomalocaris, Laggania, and Hurdia, and the differences in morphology between the frontal appendages may reflect different feeding strategies. The stratigraphically lowest locality, S7 on Mount Stephen, yields material from all anomalocaridid taxa, but the assemblages in the younger quarries on Fossil Ridge are dominated by Anomalocaris and Hurdia only. © The Palaeontological Association.

@article{doi101111j14754983201000955x,
    author = "Daley, Allison C. and Budd, Graham E.",
    title = "New anomalocaridid appendages from the Burgess Shale, Canada",
    year = "2010",
    journal = "Palaeontology",
    abstract = "Abstract: The complex history of description of the anomalocaridids has partly been caused by the fragmentary nature of these fossils. Frontal appendages and mouth parts are more readily preserved than whole-body assemblages, so the earliest work on these animals examined these structures in isolation. After several decades of research, these disarticulated elements were assembled together to reconstruct the anomalocaridid body plan, and a total of three Burgess Shale genera, Anomalocaris, Laggania and Hurdia, were described in full. Here we present new frontal appendage material of additional anomalocaridid taxa from the 'Middle' Cambrian (Series 3) Burgess Shale Formation in Canada, showing that the diversity of anomalocaridids in this locality is even higher than previously thought. Material includes Amplectobelua stephenensis sp. nov., the first known occurrence of this genus outside of China; Caryosyntrips serratus gen. et sp. nov., which is similar to the Anomalocaris appendage but has a straighter outline and a different arrangement of spines; and an appendage that may be either the Laggania appendage or a third morph of the Hurdia appendage. The new anomalocaridid material is contemporaneous with the previously described taxa Anomalocaris, Laggania, and Hurdia, and the differences in morphology between the frontal appendages may reflect different feeding strategies. The stratigraphically lowest locality, S7 on Mount Stephen, yields material from all anomalocaridid taxa, but the assemblages in the younger quarries on Fossil Ridge are dominated by Anomalocaris and Hurdia only. © The Palaeontological Association.",
    url = "https://doi.org/10.1111/j.1475-4983.2010.00955.x",
    doi = "10.1111/j.1475-4983.2010.00955.x",
    openalex = "W2102369866",
    references = "doi101666pleo050701, openalexw2601410785"
}

Molecular and morphological evidence unite the hemichordates and echinoderms as the Ambulacraria, but their earliest history remains almost entirely conjectural. This is on account of the morphological disparity of the ambulacrarians and a paucity of obvious stem-groups. We describe here a new taxon Herpetogaster collinsi gen. et sp. nov. from the Burgess Shale (Middle Cambrian) Lagerstätte. This soft-bodied vermiform animal has a pair of elongate dendritic oral tentacles, a flexible stolon with an attachment disc, and a re-curved trunk with at least 13 segments that is directed dextrally. A differentiated but un-looped gut is enclosed in a sac suspended by mesenteries. It consists of a short pharynx, a conspicuous lenticular stomach, followed by a narrow intestine sub-equal in length. This new taxon, together with the Lower Cambrian Phlogites and more intriguingly the hitherto enigmatic discoidal eldoniids (Cambrian-Devonian), form a distinctive clade (herein the cambroernids). Although one hypothesis of their relationships would look to the lophotrochozoans (specifically the entoprocts), we suggest that the evidence is more consistent with their being primitive deuterostomes, with specific comparisons being made to the pterobranch hemichordates and pre-radial echinoderms. On this basis some of the earliest ambulacrarians are interpreted as soft-bodied animals with a muscular stalk, and possessing prominent tentacles.

@article{doi101371journalpone0009586,
    author = "Caron, Jean-Bernard and Conway Morris, Simon and Shu, Degan",
    title = "Tentaculate fossils from the Cambrian of Canada (British Columbia) and China (Yunnan) interpreted as primitive deuterostomes.",
    year = "2010",
    journal = "PloS one",
    abstract = "Molecular and morphological evidence unite the hemichordates and echinoderms as the Ambulacraria, but their earliest history remains almost entirely conjectural. This is on account of the morphological disparity of the ambulacrarians and a paucity of obvious stem-groups. We describe here a new taxon Herpetogaster collinsi gen. et sp. nov. from the Burgess Shale (Middle Cambrian) Lagerstätte. This soft-bodied vermiform animal has a pair of elongate dendritic oral tentacles, a flexible stolon with an attachment disc, and a re-curved trunk with at least 13 segments that is directed dextrally. A differentiated but un-looped gut is enclosed in a sac suspended by mesenteries. It consists of a short pharynx, a conspicuous lenticular stomach, followed by a narrow intestine sub-equal in length. This new taxon, together with the Lower Cambrian Phlogites and more intriguingly the hitherto enigmatic discoidal eldoniids (Cambrian-Devonian), form a distinctive clade (herein the cambroernids). Although one hypothesis of their relationships would look to the lophotrochozoans (specifically the entoprocts), we suggest that the evidence is more consistent with their being primitive deuterostomes, with specific comparisons being made to the pterobranch hemichordates and pre-radial echinoderms. On this basis some of the earliest ambulacrarians are interpreted as soft-bodied animals with a muscular stalk, and possessing prominent tentacles.",
    url = "https://pmc.ncbi.nlm.nih.gov/articles/PMC2833208/",
    doi = "10.1371/journal.pone.0009586",
    openalex = "W2023015944",
    pmcid = "PMC2833208",
    pmid = "20221405",
    references = "doi101038nature06614, doi101098rspb20090896, doi101111j175348871981tb06752x, doi101126science9231776, doi101126science972526482b, doi1023071483846, doi1023073390, doi105860choice273873, openalexw1904943263, openalexw3104090091, openalexw645459046"
}

Palaeoscolecidan worms are an important component of many Lower Palaeozoic marine assemblages, with notable occurrences in a number of Burgess Shale-type Fossil-Lagersttten. In addition to material from the lower Cambrian Kinzers Formation and Latham Shale, we also describe two new palaeoscolecidan taxa from the lower Cambrian Sirius Passet Fossil-Lagersttte of North Greenland: Chalazoscolex pharkus gen. et sp. nov and Xystoscolex boreogyrus gen. et sp. nov. These palaeoscolecidans appear to be the oldest known (Cambrian Series 2, Stage 3) soft-bodied examples, being somewhat older than the diverse assemblages from the Chengjiang Fossil-Lagersttte of China. In the Sirius Passet taxa the body is composed of a spinose introvert (or proboscis), trunk with ornamentation that includes regions bearing cuticular ridges and sclerites, and a caudal zone with prominent circles of sclerites. The taxa are evidently quite closely related; generic differentiation is based on degree of trunk ornamentation, details of introvert structure and nature of the caudal region. The worms were probably infaunal or semi-epifaunal; gut contents suggest that at least X. boreogyrus may have preyed on the arthropod Isoxys.

@article{doi104202app20090058,
    author = "Morris, Simon Conway and Peel, John S.",
    title = "New Palaeoscolecidan Worms from the Lower Cambrian: Sirius Passet, Latham Shale and Kinzers Shale",
    year = "2010",
    journal = "Acta Palaeontologica Polonica",
    abstract = "Palaeoscolecidan worms are an important component of many Lower Palaeozoic marine assemblages, with notable occurrences in a number of Burgess Shale-type Fossil-Lagersttten. In addition to material from the lower Cambrian Kinzers Formation and Latham Shale, we also describe two new palaeoscolecidan taxa from the lower Cambrian Sirius Passet Fossil-Lagersttte of North Greenland: Chalazoscolex pharkus gen. et sp. nov and Xystoscolex boreogyrus gen. et sp. nov. These palaeoscolecidans appear to be the oldest known (Cambrian Series 2, Stage 3) soft-bodied examples, being somewhat older than the diverse assemblages from the Chengjiang Fossil-Lagersttte of China. In the Sirius Passet taxa the body is composed of a spinose introvert (or proboscis), trunk with ornamentation that includes regions bearing cuticular ridges and sclerites, and a caudal zone with prominent circles of sclerites. The taxa are evidently quite closely related; generic differentiation is based on degree of trunk ornamentation, details of introvert structure and nature of the caudal region. The worms were probably infaunal or semi-epifaunal; gut contents suggest that at least X. boreogyrus may have preyed on the arthropod Isoxys.",
    url = "https://doi.org/10.4202/app.2009.0058",
    doi = "10.4202/app.2009.0058",
    openalex = "W2049746512",
    references = "doi101016jpalwor200610016, doi101038326181a0, doi101038387489a0, doi101038nature06614, doi101098rstb19950029, doi1011111475498300229, doi101130gsab49195, doi103140bullgeosci1158, doi104202app20080110, doi105860choice416546, doi107312zhur10612, openalexw2134978213"
}

Hu, Shixue, Zhang, Zhifei, Holmer, Lars E., Skovsted, Christian B. (2010): Soft-part preservation in a linguliform brachiopod from the lower Cambrian Wulongqing Formation (Guanshan Fauna) of Yunnan, South China. Acta Palaeontologica Polonica 55 (3): 495-505, DOI: 10.4202/app.2009.1106, URL: http://dx.doi.org/10.4202/app.2009.1106

@article{doi104202app20091106,
    author = "Hu, Shixue and Zhang, Zhifei and Holmer, Lars E. and Skovsted, Christian B.",
    title = "Soft-Part Preservation in a Linguliform Brachiopod from the Lower Cambrian Wulongqing Formation (Guanshan Fauna) of Yunnan, South China",
    year = "2010",
    journal = "Acta Palaeontologica Polonica",
    abstract = "Hu, Shixue, Zhang, Zhifei, Holmer, Lars E., Skovsted, Christian B. (2010): Soft-part preservation in a linguliform brachiopod from the lower Cambrian Wulongqing Formation (Guanshan Fauna) of Yunnan, South China. Acta Palaeontologica Polonica 55 (3): 495-505, DOI: 10.4202/app.2009.1106, URL: http://dx.doi.org/10.4202/app.2009.1106",
    url = "https://doi.org/10.4202/app.2009.1106",
    doi = "10.4202/app.2009.1106",
    openalex = "W2079480991",
    references = "doi101017s0094837300002979"
}

A restudy of the Burgess Shale arthropod Emeraldella brocki suggests novel interpretations of its morphology. We show that the morphology is more plesiomorphic than previously assumed, particularly regarding tagmosis. The cephalon probably only incorporates three limb-bearing postantennular segments. The trunk is not differentiated and consists of 12 tergite-bearing segments and a styliform telson. Limb structure is generally similar to that of other artiopods except for a tripartite exopod and a high degree of differentiation of podomere proportions along the body. A phylogenetic analysis of 20 fossil arthropod taxa based on 36 characters renders E. brocki as a basal taxon within a monophyletic group that comprises all artiopods included. Autapomorphies of this taxon are a filiform antennula and a bilobate exopod that carries lamellae proximally. Trilobites are nested within a group of artiopods sharing a pygidium. Agnostus pisiformis is retrieved as the sister taxon to the stem-lineage crustacean Oelandocaris oelandica, and both constitute the sister taxon of Artiopoda. ‘Great appendage’ arthropods, traditionally included in the Arachnomorpha, are retrieved as sister to the Crustacea sensu lato + Artiopoda clade, which contradicts the arachnomorph concept.

@article{doi101080147720192011566634,
    author = "Stein, Martin and Selden, Paul A.",
    title = "A restudy of the Burgess Shale (Cambrian) arthropod Emeraldella brocki and reassessment of its affinities",
    year = "2011",
    journal = "Journal of Systematic Palaeontology",
    abstract = "A restudy of the Burgess Shale arthropod Emeraldella brocki suggests novel interpretations of its morphology. We show that the morphology is more plesiomorphic than previously assumed, particularly regarding tagmosis. The cephalon probably only incorporates three limb-bearing postantennular segments. The trunk is not differentiated and consists of 12 tergite-bearing segments and a styliform telson. Limb structure is generally similar to that of other artiopods except for a tripartite exopod and a high degree of differentiation of podomere proportions along the body. A phylogenetic analysis of 20 fossil arthropod taxa based on 36 characters renders E. brocki as a basal taxon within a monophyletic group that comprises all artiopods included. Autapomorphies of this taxon are a filiform antennula and a bilobate exopod that carries lamellae proximally. Trilobites are nested within a group of artiopods sharing a pygidium. Agnostus pisiformis is retrieved as the sister taxon to the stem-lineage crustacean Oelandocaris oelandica, and both constitute the sister taxon of Artiopoda. ‘Great appendage’ arthropods, traditionally included in the Arachnomorpha, are retrieved as sister to the Crustacea sensu lato + Artiopoda clade, which contradicts the arachnomorph concept.",
    url = "https://doi.org/10.1080/14772019.2011.566634",
    doi = "10.1080/14772019.2011.566634",
    openalex = "W2149698609",
    references = "doi10108003115510508619300, doi10108011035890809452772, doi101098rstb19810033, doi101111j10963642200900562x, doi101666060821, doi104095103458, openalexw2240758963"
}

Abstract: We redescribe the morphology of Yohoia tenuis (Chelicerata sensu lato) from the Cambrian Burgess Shale Lagerstätte. The morphology of the most anterior, prominent, so‐called great appendage changes throughout ontogeny. While its principal morphology remains unaltered, the length ratios of certain parts of the great appendage change significantly. Furthermore, it possesses a special jack‐knifing mechanism, i.e. an elbow joint: the articulation between the distal one of the two peduncle elements and the most proximal of the four spine‐bearing claw elements. This morphology might have enabled the animal to hunt like a modern spearer‐type mantis shrimp, an analogy enhanced by the similarly large and protruding eyes. For comparison, details of specimens of selected other great‐appendage arthropods from the Lower Cambrian Chengjiang Lagerstätte have been investigated using fluorescence microscopy. This revealed that the morphology of the great appendage of Y. tenuis is much like that of the Chengjiang species Fortiforceps foliosa and Jianfengia multisegmentalis. The morphology of the great appendage of the latter is even more similar to the morphology developed in early developmental stages of Y. tenuis, while the morphology of the great appendage of F. foliosa is more similar to that of later developmental stages of Y. tenuis. The arrangement of the elbow joint supports the view that the great appendage evolved into the chelicera of Chelicerata sensu stricto, as similar joints are found in various ingroup taxa such as Xiphosura, Opiliones or Palpigradi. With this, it also supports the interpretation of the great appendage to be homologous with the first appendage of other arthropods.

@article{doi101111j14754983201101124x,
    author = "Haug, Joachim T. and Waloszek, Dieter and Maas, Andreas and Liu, Yu and Haug, Carolin",
    title = "Functional morphology, ontogeny and evolution of mantis shrimp‐like predators in the Cambrian",
    year = "2011",
    journal = "Palaeontology",
    abstract = "Abstract: We redescribe the morphology of Yohoia tenuis (Chelicerata sensu lato) from the Cambrian Burgess Shale Lagerstätte. The morphology of the most anterior, prominent, so‐called great appendage changes throughout ontogeny. While its principal morphology remains unaltered, the length ratios of certain parts of the great appendage change significantly. Furthermore, it possesses a special jack‐knifing mechanism, i.e. an elbow joint: the articulation between the distal one of the two peduncle elements and the most proximal of the four spine‐bearing claw elements. This morphology might have enabled the animal to hunt like a modern spearer‐type mantis shrimp, an analogy enhanced by the similarly large and protruding eyes. For comparison, details of specimens of selected other great‐appendage arthropods from the Lower Cambrian Chengjiang Lagerstätte have been investigated using fluorescence microscopy. This revealed that the morphology of the great appendage of Y. tenuis is much like that of the Chengjiang species Fortiforceps foliosa and Jianfengia multisegmentalis. The morphology of the great appendage of the latter is even more similar to the morphology developed in early developmental stages of Y. tenuis, while the morphology of the great appendage of F. foliosa is more similar to that of later developmental stages of Y. tenuis. The arrangement of the elbow joint supports the view that the great appendage evolved into the chelicera of Chelicerata sensu stricto, as similar joints are found in various ingroup taxa such as Xiphosura, Opiliones or Palpigradi. With this, it also supports the interpretation of the great appendage to be homologous with the first appendage of other arthropods.",
    url = "https://doi.org/10.1111/j.1475-4983.2011.01124.x",
    doi = "10.1111/j.1475-4983.2011.01124.x",
    openalex = "W1562077884",
    references = "doi101007s0042700600854, doi101016jasd200501005, doi101017s002233600002758x, doi101038428819a, doi10108010635150390218330, doi10108011035890809452772, doi10108011035899509546213, doi101098rspb20090361, doi101098rstb19830020, doi101111j10963642200700284x, doi101111j10963642200900562x, doi101111j14754983200700649x, doi101111j14754983200900914x, doi101111j150239311999tb00547x, doi101126science1169514, doi101139e06012, doi101146annureven10010165000525, doi101242jeb01831, doi101666060171, doi101826182000751171987, doi1023072992562, doi1023073515467, doi104095103458, doi105281zenodo15992748, doi105281zenodo16490103, doi105860choice416546, doi105962bhltitle14915, doi105962bhltitle156765, maas2003morphology, openalexw2240758963, xianguang1999new"
}

The Middle Cambrian Pikaia gracilens (Walcott) has an iconic position as a Cambrian chordate, but until now no detailed description has been available. Here on the basis of the 114 available specimens we review its anatomy, confirm its place in the chordates and explore with varying degrees of confidence its relationships to both extant and extinct chordates and other deuterostomes. The body of Pikaia is fusiform, laterally compressed and possesses about 100 myomeres. The head is small, bilobed and bears two narrow tentacles. There is no evidence for eyes. Apart from a thin dorsal fin (without finrays) and a series of at least nine bilaterally arranged appendages with possible pharyngeal pores at the anterior end, there are no other external features. In addition to the musculature the internal anatomy includes an alimentary canal, the anterior of which forms a prominent lenticular unit that is almost invariably preserved in positive relief. The cavity is interpreted as pharyngeal, implying that the mouth itself was almost terminal. The posterior extension of the gut is unclear although the anus appears to have been terminal. The most prominent internal structure is a reflectively preserved unit, possibly hollow, termed here the dorsal organ. Although formerly interpreted as a notochord its position and size make this less likely. Its original function remains uncertain, but it could have formed a storage organ. Ventral to the dorsal organ a narrower strand of tissue is interpreted as representing the nerve chord and notochord. In addition to these structures, there is also evidence for a vascular system, including a ventral blood vessel. The position of Pikaia in the chordates is largely based on the presence of sigmoidal myomeres, and the more tentative identification of a notochord. In many other respects, Pikaia differs from the expected nature of primitive chordates, especially as revealed in amphioxus and the Cambrian record (including Cathaymyrus, Haikouichthys, Metaspriggina, Myllokunmingia, and Zhongxiniscus). Whilst the possibility that Pikaia is simply convergent on the chordates cannot be dismissed, we prefer to build a scenario that regards Pikaia as the most stem-ward of the chordates with links to the phylogenetically controversial yunnanozoans. This hypothesis has implications for the evolution of the myomeres, notochord and gills. Finally, the wealth of material of Pikaia indicates that, although by definition there must be some sort of taphonomic imprint, the consistency of preservational details allows a reliable reconstruction of the anatomy and does not significantly erode phylogenetically relevant characters.

@article{doi101111j1469185x201200220x,
    author = "Morris, Simon Conway and Caron, Jean‐Bernard",
    title = "Pikaia gracilens Walcott, a stem‐group chordate from the Middle Cambrian of British Columbia",
    year = "2012",
    journal = "Biological reviews/Biological reviews of the Cambridge Philosophical Society",
    abstract = "The Middle Cambrian Pikaia gracilens (Walcott) has an iconic position as a Cambrian chordate, but until now no detailed description has been available. Here on the basis of the 114 available specimens we review its anatomy, confirm its place in the chordates and explore with varying degrees of confidence its relationships to both extant and extinct chordates and other deuterostomes. The body of Pikaia is fusiform, laterally compressed and possesses about 100 myomeres. The head is small, bilobed and bears two narrow tentacles. There is no evidence for eyes. Apart from a thin dorsal fin (without finrays) and a series of at least nine bilaterally arranged appendages with possible pharyngeal pores at the anterior end, there are no other external features. In addition to the musculature the internal anatomy includes an alimentary canal, the anterior of which forms a prominent lenticular unit that is almost invariably preserved in positive relief. The cavity is interpreted as pharyngeal, implying that the mouth itself was almost terminal. The posterior extension of the gut is unclear although the anus appears to have been terminal. The most prominent internal structure is a reflectively preserved unit, possibly hollow, termed here the dorsal organ. Although formerly interpreted as a notochord its position and size make this less likely. Its original function remains uncertain, but it could have formed a storage organ. Ventral to the dorsal organ a narrower strand of tissue is interpreted as representing the nerve chord and notochord. In addition to these structures, there is also evidence for a vascular system, including a ventral blood vessel. The position of Pikaia in the chordates is largely based on the presence of sigmoidal myomeres, and the more tentative identification of a notochord. In many other respects, Pikaia differs from the expected nature of primitive chordates, especially as revealed in amphioxus and the Cambrian record (including Cathaymyrus, Haikouichthys, Metaspriggina, Myllokunmingia, and Zhongxiniscus). Whilst the possibility that Pikaia is simply convergent on the chordates cannot be dismissed, we prefer to build a scenario that regards Pikaia as the most stem-ward of the chordates with links to the phylogenetically controversial yunnanozoans. This hypothesis has implications for the evolution of the myomeres, notochord and gills. Finally, the wealth of material of Pikaia indicates that, although by definition there must be some sort of taphonomic imprint, the consistency of preservational details allows a reliable reconstruction of the anatomy and does not significantly erode phylogenetically relevant characters.",
    url = "https://doi.org/10.1111/j.1469-185x.2012.00220.x",
    doi = "10.1111/j.1469-185x.2012.00220.x",
    openalex = "W1973056168",
    references = "barrington1937vi, doi1010160012825272900724, doi101017s0006323199005472, doi10103846965, doi101038nature01264, doi101038nature02709, doi101038nature04336, doi101038nature06967, doi101093icb431166, doi101111j14697998200800497x, doi101126science1194167, doi101666061301, openalexw2134978213"
}

Burgess Shale-type deposits provide invaluable insights into the early evolution of body plans and the ecological structure of Cambrian communities, but a number of species, continue to defy phylogenetic interpretations. Here we extend this list to include a new soft-bodied animal, Siphusauctum gregarium n. gen. and n. sp., from the Tulip Beds (Campsite Cliff Shale Member, Burgess Shale Formation) of Mount Stephen (Yoho National Park, British Columbia). With 1,133 specimens collected, S. gregarium is clearly the most abundant animal from this locality.This stalked animal (reaching at least 20 cm in length), has a large ovoid calyx connected to a narrow bilayered stem and a small flattened or bulb-like holdfast. The calyx is enclosed by a flexible sheath with six small openings at the base, and a central terminal anus near the top encircled by indistinct openings. A prominent organ, represented by six radially symmetrical segments with comb-like elements, surrounds an internal body cavity with a large stomach, conical median gut and straight intestine. Siphusauctum gregarium was probably an active filter-feeder, with water passing through the calyx openings, capturing food particles with its comb-like elements. It often occurs in large assemblages on single bedding planes suggesting a gregarious lifestyle, with the animal living in high tier clusters. These were probably buried en masse more or less in-situ by rapid mud flow events.Siphusauctum gregarium resembles Dinomischus, another Cambrian enigmatic stalked animal. Principal points of comparison include a long stem with a calyx containing a visceral mass and bract-like elements, and a similar lifestyle albeit occupying different tiering levels. The presence in both animals of a digestive tract with a potential stomach and anus suggest a grade of organization within bilaterians, but relationships with extant phyla are not straightforward. Thus, the broader affinities of S. gregarium remain largely unconstrained.

@article{doi101371journalpone0029233,
    author = "O’Brien, Lorna J. and Caron, Jean‐Bernard",
    title = "A New Stalked Filter-Feeder from the Middle Cambrian Burgess Shale, British Columbia, Canada",
    year = "2012",
    journal = "PLoS ONE",
    abstract = "Burgess Shale-type deposits provide invaluable insights into the early evolution of body plans and the ecological structure of Cambrian communities, but a number of species, continue to defy phylogenetic interpretations. Here we extend this list to include a new soft-bodied animal, Siphusauctum gregarium n. gen. and n. sp., from the Tulip Beds (Campsite Cliff Shale Member, Burgess Shale Formation) of Mount Stephen (Yoho National Park, British Columbia). With 1,133 specimens collected, S. gregarium is clearly the most abundant animal from this locality.This stalked animal (reaching at least 20 cm in length), has a large ovoid calyx connected to a narrow bilayered stem and a small flattened or bulb-like holdfast. The calyx is enclosed by a flexible sheath with six small openings at the base, and a central terminal anus near the top encircled by indistinct openings. A prominent organ, represented by six radially symmetrical segments with comb-like elements, surrounds an internal body cavity with a large stomach, conical median gut and straight intestine. Siphusauctum gregarium was probably an active filter-feeder, with water passing through the calyx openings, capturing food particles with its comb-like elements. It often occurs in large assemblages on single bedding planes suggesting a gregarious lifestyle, with the animal living in high tier clusters. These were probably buried en masse more or less in-situ by rapid mud flow events.Siphusauctum gregarium resembles Dinomischus, another Cambrian enigmatic stalked animal. Principal points of comparison include a long stem with a calyx containing a visceral mass and bract-like elements, and a similar lifestyle albeit occupying different tiering levels. The presence in both animals of a digestive tract with a potential stomach and anus suggest a grade of organization within bilaterians, but relationships with extant phyla are not straightforward. Thus, the broader affinities of S. gregarium remain largely unconstrained.",
    url = "https://doi.org/10.1371/journal.pone.0029233",
    doi = "10.1371/journal.pone.0029233",
    openalex = "W2091763056",
    references = "doi101016jpalaeo200705023, doi101017s000632310000548x, doi101093icb431166, doi101111j14754983200700656x, doi101126science1169514, doi101371journalpone0009586, doi1016660094837320020280155lgatio20co2, doi1023072992562, doi105860choice273873, openalexw2754161204, openalexw3127114020"
}

Present-day ecosystems host a huge variety of organisms that interact and transfer mass and energy via a cascade of trophic levels. When and how this complex machinery was established remains largely unknown. Although exceptionally preserved biotas clearly show that Early Cambrian animals had already acquired functionalities that enabled them to exploit a wide range of food resources, there is scant direct evidence concerning their diet and exact trophic relationships. Here I describe the gut contents of Ottoia prolifica, an abundant priapulid worm from the middle Cambrian (Stage 5) Burgess Shale biota. I identify the undigested exoskeletal remains of a wide range of small invertebrates that lived at or near the water sediment interface such as hyolithids, brachiopods, different types of arthropods, polychaetes and wiwaxiids. This set of direct fossil evidence allows the first detailed reconstruction of the diet of a 505-million-year-old animal. Ottoia was a dietary generalist and had no strict feeding regime. It fed on both living individuals and decaying organic matter present in its habitat. The feeding behavior of Ottoia was remarkably simple, reduced to the transit of food through an eversible pharynx and a tubular gut with limited physical breakdown and no storage. The recognition of generalist feeding strategies, exemplified by Ottoia, reveals key-aspects of modern-style trophic complexity in the immediate aftermath of the Cambrian explosion. It also shows that the middle Cambrian ecosystem was already too complex to be understood in terms of simple linear dynamics and unique pathways.

@article{doi101371journalpone0052200,
    author = "Vannier, Jean",
    title = "Gut Contents as Direct Indicators for Trophic Relationships in the Cambrian Marine Ecosystem",
    year = "2012",
    journal = "PLoS ONE",
    abstract = "Present-day ecosystems host a huge variety of organisms that interact and transfer mass and energy via a cascade of trophic levels. When and how this complex machinery was established remains largely unknown. Although exceptionally preserved biotas clearly show that Early Cambrian animals had already acquired functionalities that enabled them to exploit a wide range of food resources, there is scant direct evidence concerning their diet and exact trophic relationships. Here I describe the gut contents of Ottoia prolifica, an abundant priapulid worm from the middle Cambrian (Stage 5) Burgess Shale biota. I identify the undigested exoskeletal remains of a wide range of small invertebrates that lived at or near the water sediment interface such as hyolithids, brachiopods, different types of arthropods, polychaetes and wiwaxiids. This set of direct fossil evidence allows the first detailed reconstruction of the diet of a 505-million-year-old animal. Ottoia was a dietary generalist and had no strict feeding regime. It fed on both living individuals and decaying organic matter present in its habitat. The feeding behavior of Ottoia was remarkably simple, reduced to the transit of food through an eversible pharynx and a tubular gut with limited physical breakdown and no storage. The recognition of generalist feeding strategies, exemplified by Ottoia, reveals key-aspects of modern-style trophic complexity in the immediate aftermath of the Cambrian explosion. It also shows that the middle Cambrian ecosystem was already too complex to be understood in terms of simple linear dynamics and unique pathways.",
    url = "https://doi.org/10.1371/journal.pone.0052200",
    doi = "10.1371/journal.pone.0052200",
    openalex = "W2088717921",
    references = "doi1010079781461501619, doi101016jpalaeo200705023, doi101073pnas0903474106, doi10108000241160410004764, doi101098rspb20090361, doi101098rstb19810164, doi101098rstb20140313, doi101111j14610248200400606x, doi101111j14754983200700656x, doi101146annurevearth33092203122519, doi101371journalpbio0060102, doi101371journalpone0029233, doi101666060821, doi102110palo2003p05070r, doi102110palo2009p09004r, openalexw1573076930, openalexw2604533467, openalexw2754161204, openalexw2912219260, openalexw659399033"
}

In Cambrian fossil Lagerstätten like the Burgess Shale, exceptionally preserved arthropods constitute a large part of the taxonomic diversity, providing opportunities to study the early evolution of this phylum in detail. The anomalocaridids, large presumed pelagic predators, are particularly relevant owing to their unique combination of morphological characters and basal position in the arthropod stem lineage. Although isolated elements and fragmented specimens were first discovered over 100 years ago, subsequent findings of more complete bodies of Anomalocaris and Peytoia, especially in the 1980s, allowed for a better understanding of these enigmatic forms. Their evolutionary significance as stem group arthropods was further clarified by the recent discovery of a third anomalocaridid taxon, Hurdia. Here, examination of hundreds of Hurdia specimens from different stratigraphical layers within the Burgess Shale and Stephen Formation, combined with statistical analyses, provides a detailed description of the taphonomy, morphology and diversity of the genus and further elucidates anomalocaridid systematics. Hurdia is distinguished from other anomalocaridids in having mouthparts with extra rows of teeth, a large frontal carapace complex and diminutive swimming flaps with prominent setal structures. The two original species, H. victoria Walcott, 1912 and H. triangulata Walcott, 1912, are confirmed based on morphometric outline analyses of the frontal carapace components combined with stratigraphical evidence; a third species, Hurdia dentata Simonetta & Delle Cave, 1975, is synonymized with H. victoria. Morphology, preservation and stratigraphical distribution suggest that H. victoria and H. triangulata share the same type of frontal appendage; a second type of appendage, previously assigned to Hurdia (Morph A), belongs to Peytoia nathorsti. These and other morphological differences between the anomalocaridids may reflect different feeding strategies. Appendages and mouthparts of Hurdia indet. sp. are also identified from the Spence Shale Member of Utah, making Hurdia and Anomalocaris the most common and globally distributed anomalocaridid taxa.

@article{doi101080147720192012732723,
    author = "Daley, Allison C. and Budd, Graham E. and Caron, Jean‐Bernard",
    title = "Morphology and systematics of the anomalocaridid arthropod Hurdia from the Middle Cambrian of British Columbia and Utah",
    year = "2013",
    journal = "Journal of Systematic Palaeontology",
    abstract = "In Cambrian fossil Lagerstätten like the Burgess Shale, exceptionally preserved arthropods constitute a large part of the taxonomic diversity, providing opportunities to study the early evolution of this phylum in detail. The anomalocaridids, large presumed pelagic predators, are particularly relevant owing to their unique combination of morphological characters and basal position in the arthropod stem lineage. Although isolated elements and fragmented specimens were first discovered over 100 years ago, subsequent findings of more complete bodies of Anomalocaris and Peytoia, especially in the 1980s, allowed for a better understanding of these enigmatic forms. Their evolutionary significance as stem group arthropods was further clarified by the recent discovery of a third anomalocaridid taxon, Hurdia. Here, examination of hundreds of Hurdia specimens from different stratigraphical layers within the Burgess Shale and Stephen Formation, combined with statistical analyses, provides a detailed description of the taphonomy, morphology and diversity of the genus and further elucidates anomalocaridid systematics. Hurdia is distinguished from other anomalocaridids in having mouthparts with extra rows of teeth, a large frontal carapace complex and diminutive swimming flaps with prominent setal structures. The two original species, H. victoria Walcott, 1912 and H. triangulata Walcott, 1912, are confirmed based on morphometric outline analyses of the frontal carapace components combined with stratigraphical evidence; a third species, Hurdia dentata Simonetta \& Delle Cave, 1975, is synonymized with H. victoria. Morphology, preservation and stratigraphical distribution suggest that H. victoria and H. triangulata share the same type of frontal appendage; a second type of appendage, previously assigned to Hurdia (Morph A), belongs to Peytoia nathorsti. These and other morphological differences between the anomalocaridids may reflect different feeding strategies. Appendages and mouthparts of Hurdia indet. sp. are also identified from the Spence Shale Member of Utah, making Hurdia and Anomalocaris the most common and globally distributed anomalocaridid taxa.",
    url = "https://doi.org/10.1080/14772019.2012.732723",
    doi = "10.1080/14772019.2012.732723",
    openalex = "W2095162853",
    references = "doi10100797894009919727, doi1010160146664x8290034x, doi101016jpalaeo200902013, doi101038114085a0, doi10108003115519608619475, doi101093sysbio34159, doi101242jcss2935309, doi101371journalpone0029233, doi101666pleo050701, doi101826182003769311997, doi1023072413345, doi1023072992562, doi104202app20090058, doi105281zenodo16273729"
}

Lagerstätten from the Precambrian–Cambrian transition have traditionally been a relatively untapped resource for understanding the paleoecology of the “Cambrian explosion.” This quantitative paleoecological study is based on 10,238 fossil specimens belonging to 100 animal species, 11 phyla, and 15 ecological categories from the lower Cambrian (Series 2, Stage 3) Chengjiang biota (Mafang locality near Haikou, Yunnan Province, China). Fossils were systematically collected within a 2.5-meter-thick sequence divided into ten stratigraphic intervals. Each interval represents an induced time-averaged assemblage of various event (obrution) beds of unknown duration. Overall, the different fossil assemblages are taxonomically and ecologically similar, suggesting the presence of a single community type recurring throughout the Mafang section. The Mafang community is dominated by epibenthic vagile hunters or scavengers, sessile suspension feeders, and infaunal vagile hunters or scavengers represented primarily by arthropods, brachiopods, and priapulids, respectively. Most species have low abundance and low occurrence frequencies, whereas a few species are numerically abundant and occur frequently. Overall, in structure and ecology the Mafang community is comparable to the Middle Cambrian (Series 3, Stage 5) Burgess Shale biota (Walcott Quarry, Yoho National Park, British Columbia, Canada). This suggests that, despite variations in species identity within taxonomic and ecological groups, the structure and ecology of Cambrian Burgess Shale-type communities remained relatively stable until at least the Middle Cambrian (Series 3, Stage 5) in subtidal to relatively deep-water offshore settings in siliciclastic soft-substrate environments.

@article{doi10166612056,
    author = "Zhao, Fangchen and Caron, Jean‐Bernard and Bottjer, David J. and Hu, Shixue and Yin, Zongjun and Zhu, Maoyan",
    title = "Diversity and species abundance patterns of the Early Cambrian (Series 2, Stage 3) Chengjiang Biota from China",
    year = "2013",
    journal = "Paleobiology",
    abstract = "Lagerstätten from the Precambrian–Cambrian transition have traditionally been a relatively untapped resource for understanding the paleoecology of the “Cambrian explosion.” This quantitative paleoecological study is based on 10,238 fossil specimens belonging to 100 animal species, 11 phyla, and 15 ecological categories from the lower Cambrian (Series 2, Stage 3) Chengjiang biota (Mafang locality near Haikou, Yunnan Province, China). Fossils were systematically collected within a 2.5-meter-thick sequence divided into ten stratigraphic intervals. Each interval represents an induced time-averaged assemblage of various event (obrution) beds of unknown duration. Overall, the different fossil assemblages are taxonomically and ecologically similar, suggesting the presence of a single community type recurring throughout the Mafang section. The Mafang community is dominated by epibenthic vagile hunters or scavengers, sessile suspension feeders, and infaunal vagile hunters or scavengers represented primarily by arthropods, brachiopods, and priapulids, respectively. Most species have low abundance and low occurrence frequencies, whereas a few species are numerically abundant and occur frequently. Overall, in structure and ecology the Mafang community is comparable to the Middle Cambrian (Series 3, Stage 5) Burgess Shale biota (Walcott Quarry, Yoho National Park, British Columbia, Canada). This suggests that, despite variations in species identity within taxonomic and ecological groups, the structure and ecology of Cambrian Burgess Shale-type communities remained relatively stable until at least the Middle Cambrian (Series 3, Stage 5) in subtidal to relatively deep-water offshore settings in siliciclastic soft-substrate environments.",
    url = "https://doi.org/10.1666/12056",
    doi = "10.1666/12056",
    openalex = "W2165047391",
    references = "doi10103846965, doi101038nature01264, doi101086321317, doi101111j1469185x201200220x, doi101111pala12042, doi101126science1189910, doi101126science1206375, doi101666061301, doi1018901119521, doi102110palo2009p09004r, doi1023071934145, doi105860choice416546, doi105860choice421547, openalexw2183707334"
}

In 1909 Charles Walcott discovered the remarkable soft-bodied animal fauna of the Middle Cambrian age Burgess Shale in British Columbia. These fossils have become the iconic representation of the astonishing expansion of animal diversity during the Cambrian, including the first appearance in the fossil record of essentially all living phyla, known as the “Cambrian explosion.” Although the Burgess Shale biota is the public face of the Cambrian explosion, even appearing on a 1995 cover of Time, it is only a small part of the story (and somewhat late in the tale). Most readers will be familiar with the Cambrian explosion through Stephen Jay Gould’s 1989 book Wonderful Life (1989) or perhaps Martin Brasier’s more recent Darwin’s Lost World (2009). Both of these books were written to reach a general audience. What has been lacking to date is a more technical book, aimed at students and professionals, which summarizes and introduces the tremendous amount of research that this episode of earth history has received in the last 25 years. The Cambrian Explosion: The Construction of Animal Biodiversity by Douglas H Erwin and James W Valentine more than fills this need. It will become required reading for anyone who wants to understand the multiple lines of evidence, from geology, geochemistry, paleontology, genetics, phylogenetics, comparative morphology, and ecology, that have to be integrated to understand one of the most important episodes in the history of life. The authors, both paleontologists, are deeply respected authorities on evolution and the Cambrian fossil record, with a welldeserved reputation for innovative approaches. This book necessarily covers a tremendous amount of ground; the forty-two pages of references demonstrate the depth and breadth of scholarship that the authors summarize. The first section covers the geological context of the explosion, stretching back to the Snowball Earth episodes of the Cryogenian. This includes summaries of the current status of the absolute and relative time scales for this period and what geochemical proxies reveal about ocean chemistry, including oxygenation states and changes in the carbon cycle. The latter is unfortunately the weakest part of the book; there is very poor integration between figures (which come from external sources) and text; the figure captions and labels are inadequate. The book hits its stride in the next section. It begins with a brief review of phylogenetics and of living metazoan morphology and relationships, a subject Valentine explored in more depth in his comprehensive earlier book, On the Origin of Phyla (2004). This is followed

@article{doi105860choice510294,
    title = "The Cambrian explosion: the construction of animal biodiversity",
    year = "2013",
    journal = "Choice Reviews Online",
    abstract = "In 1909 Charles Walcott discovered the remarkable soft-bodied animal fauna of the Middle Cambrian age Burgess Shale in British Columbia. These fossils have become the iconic representation of the astonishing expansion of animal diversity during the Cambrian, including the first appearance in the fossil record of essentially all living phyla, known as the “Cambrian explosion.” Although the Burgess Shale biota is the public face of the Cambrian explosion, even appearing on a 1995 cover of Time, it is only a small part of the story (and somewhat late in the tale). Most readers will be familiar with the Cambrian explosion through Stephen Jay Gould’s 1989 book Wonderful Life (1989) or perhaps Martin Brasier’s more recent Darwin’s Lost World (2009). Both of these books were written to reach a general audience. What has been lacking to date is a more technical book, aimed at students and professionals, which summarizes and introduces the tremendous amount of research that this episode of earth history has received in the last 25 years. The Cambrian Explosion: The Construction of Animal Biodiversity by Douglas H Erwin and James W Valentine more than fills this need. It will become required reading for anyone who wants to understand the multiple lines of evidence, from geology, geochemistry, paleontology, genetics, phylogenetics, comparative morphology, and ecology, that have to be integrated to understand one of the most important episodes in the history of life. The authors, both paleontologists, are deeply respected authorities on evolution and the Cambrian fossil record, with a welldeserved reputation for innovative approaches. This book necessarily covers a tremendous amount of ground; the forty-two pages of references demonstrate the depth and breadth of scholarship that the authors summarize. The first section covers the geological context of the explosion, stretching back to the Snowball Earth episodes of the Cryogenian. This includes summaries of the current status of the absolute and relative time scales for this period and what geochemical proxies reveal about ocean chemistry, including oxygenation states and changes in the carbon cycle. The latter is unfortunately the weakest part of the book; there is very poor integration between figures (which come from external sources) and text; the figure captions and labels are inadequate. The book hits its stride in the next section. It begins with a brief review of phylogenetics and of living metazoan morphology and relationships, a subject Valentine explored in more depth in his comprehensive earlier book, On the Origin of Phyla (2004). This is followed",
    url = "https://doi.org/10.5860/choice.51-0294",
    doi = "10.5860/choice.51-0294",
    openalex = "W303205006",
    references = "doi105962bhltitle66379"
}

@misc{crossref2014cambrian,
    title = "CAMBRIAN",
    year = "2014",
    booktitle = "Encyclopedia of Environmental Change",
    url = "https://doi.org/10.4135/9781446247501.n532",
    doi = "10.4135/9781446247501.n532"
}

Burgess Shale-type fossil assemblages provide a unique record of animal life in the immediate aftermath of the so-called “Cambrian explosion.” While most soft-bodied faunas in the rock record were conserved by mineral replication of soft tissues, Burgess Shale-type preservation involved the conservation of whole assemblages of soft-bodied animals as primary carbonaceous remains, often preserved in extraordinary anatomical detail. Burgess Shale-type preservation resulted from a combination of influences operating at both local and global scales that acted to drastically slow microbial degradation in the early burial environment, resulting in incomplete decomposition and the conservation of soft-bodied animals, many of which are otherwise unknown from the fossil record. While Burgess Shale-type fossil assemblages are primarily restricted to early and middle Cambrian strata (Series 2–3), their anomalous preservation is a pervasive phenomenon that occurs widely in mudstone successions deposited on multiple paleocontinents. Herein, circumstances that led to the preservation of Burgess Shale-type fossils in Cambrian strata worldwide are reviewed. A three-tiered rank classification of the more than 50 Burgess Shale-type deposits now known is proposed and is used to consider the hierarchy of controls that regulated the operation of Burgess Shale-type preservation in space and time, ultimately determining the total number of preserved taxa and the fidelity of preservation in each deposit. While Burgess Shale-type preservation is a unique taphonomic mode that ultimately was regulated by the influence of global seawater chemistry upon the early diagenetic environment, physical depositional (biostratinomic) controls are shown to have been critical in determining the total number of taxa preserved in fossil assemblages, and hence, in regulating many of the important differences among Burgess Shale-type deposits.

@article{doi101017s1089332600002837,
    author = "Gaines, Robert R.",
    title = "Burgess Shale-type Preservation and its Distribution in Space and Time",
    year = "2014",
    journal = "The Paleontological Society Papers",
    abstract = "Burgess Shale-type fossil assemblages provide a unique record of animal life in the immediate aftermath of the so-called “Cambrian explosion.” While most soft-bodied faunas in the rock record were conserved by mineral replication of soft tissues, Burgess Shale-type preservation involved the conservation of whole assemblages of soft-bodied animals as primary carbonaceous remains, often preserved in extraordinary anatomical detail. Burgess Shale-type preservation resulted from a combination of influences operating at both local and global scales that acted to drastically slow microbial degradation in the early burial environment, resulting in incomplete decomposition and the conservation of soft-bodied animals, many of which are otherwise unknown from the fossil record. While Burgess Shale-type fossil assemblages are primarily restricted to early and middle Cambrian strata (Series 2–3), their anomalous preservation is a pervasive phenomenon that occurs widely in mudstone successions deposited on multiple paleocontinents. Herein, circumstances that led to the preservation of Burgess Shale-type fossils in Cambrian strata worldwide are reviewed. A three-tiered rank classification of the more than 50 Burgess Shale-type deposits now known is proposed and is used to consider the hierarchy of controls that regulated the operation of Burgess Shale-type preservation in space and time, ultimately determining the total number of preserved taxa and the fidelity of preservation in each deposit. While Burgess Shale-type preservation is a unique taphonomic mode that ultimately was regulated by the influence of global seawater chemistry upon the early diagenetic environment, physical depositional (biostratinomic) controls are shown to have been critical in determining the total number of taxa preserved in fossil assemblages, and hence, in regulating many of the important differences among Burgess Shale-type deposits.",
    url = "https://doi.org/10.1017/s1089332600002837",
    doi = "10.1017/s1089332600002837",
    openalex = "W3021781741",
    references = "briggs2003the, doi1010160016703784900899, doi101016jchemgeo200409003, doi101016jchemgeo200602012, doi101016jgca200511032, doi101016jpalaeo200306001, doi101016jpalaeo200407034, doi101016jpalaeo200705023, doi101016jpalaeo201003048, doi101016jpalaeo201202009, doi101017s1089332600002795, doi101038296643a0, doi101038nature08745, doi101038nature09038, doi101038nature10689, doi101038ncomms4210, doi101038ncomms4560, doi101073pnas1111784109, doi10108001490458709385971, doi101111j14754983200700656x, doi101126science1206375, doi101126science2224620163, doi1011300091761319950231079isbapo23co2, doi101130g206401, doi101130g24961a1, doi101139e06012, doi101146annurevearth33031504103001, doi102110palo2003p05070r, doi102110palo2009p09004r, doi102475ajs2929659"
}

Knowledge of the early evolution of fish largely depends on soft-bodied material from the Lower (Series 2) Cambrian period of South China. Owing to the rarity of some of these forms and a general lack of comparative material from other deposits, interpretations of various features remain controversial, as do their wider relationships amongst post-Cambrian early un-skeletonized jawless vertebrates. Here we redescribe Metaspriggina on the basis of new material from the Burgess Shale and exceptionally preserved material collected near Marble Canyon, British Columbia, and three other Cambrian Burgess Shale-type deposits from Laurentia. This primitive fish displays unambiguous vertebrate features: a notochord, a pair of prominent camera-type eyes, paired nasal sacs, possible cranium and arcualia, W-shaped myomeres, and a post-anal tail. A striking feature is the branchial area with an array of bipartite bars. Apart from the anterior-most bar, which appears to be slightly thicker, each is associated with externally located gills, possibly housed in pouches. Phylogenetic analysis places Metaspriggina as a basal vertebrate, apparently close to the Chengjiang taxa Haikouichthys and Myllokunmingia, demonstrating also that this primitive group of fish was cosmopolitan during Lower-Middle Cambrian times (Series 2-3). However, the arrangement of the branchial region in Metaspriggina has wider implications for reconstructing the morphology of the primitive vertebrate. Each bipartite bar is identified as being respectively equivalent to an epibranchial and ceratobranchial. This configuration suggests that a bipartite arrangement is primitive and reinforces the view that the branchial basket of lampreys is probably derived. Other features of Metaspriggina, including the external position of the gills and possible absence of a gill opposite the more robust anterior-most bar, are characteristic of gnathostomes and so may be primitive within vertebrates.

@article{doi101038nature13414,
    author = "Morris, Simon Conway and Caron, Jean-Bernard",
    title = "A primitive fish from the Cambrian of North America.",
    year = "2014",
    journal = "Nature",
    abstract = "Knowledge of the early evolution of fish largely depends on soft-bodied material from the Lower (Series 2) Cambrian period of South China. Owing to the rarity of some of these forms and a general lack of comparative material from other deposits, interpretations of various features remain controversial, as do their wider relationships amongst post-Cambrian early un-skeletonized jawless vertebrates. Here we redescribe Metaspriggina on the basis of new material from the Burgess Shale and exceptionally preserved material collected near Marble Canyon, British Columbia, and three other Cambrian Burgess Shale-type deposits from Laurentia. This primitive fish displays unambiguous vertebrate features: a notochord, a pair of prominent camera-type eyes, paired nasal sacs, possible cranium and arcualia, W-shaped myomeres, and a post-anal tail. A striking feature is the branchial area with an array of bipartite bars. Apart from the anterior-most bar, which appears to be slightly thicker, each is associated with externally located gills, possibly housed in pouches. Phylogenetic analysis places Metaspriggina as a basal vertebrate, apparently close to the Chengjiang taxa Haikouichthys and Myllokunmingia, demonstrating also that this primitive group of fish was cosmopolitan during Lower-Middle Cambrian times (Series 2-3). However, the arrangement of the branchial region in Metaspriggina has wider implications for reconstructing the morphology of the primitive vertebrate. Each bipartite bar is identified as being respectively equivalent to an epibranchial and ceratobranchial. This configuration suggests that a bipartite arrangement is primitive and reinforces the view that the branchial basket of lampreys is probably derived. Other features of Metaspriggina, including the external position of the gills and possible absence of a gill opposite the more robust anterior-most bar, are characteristic of gnathostomes and so may be primitive within vertebrates.",
    url = "https://pubmed.ncbi.nlm.nih.gov/24919146/",
    doi = "10.1038/nature13414",
    openalex = "W2085054285",
    pmid = "24919146",
    references = "doi101016jydbio201208026, doi10103846965, doi101038nature01264, doi101038nature05150, doi101038nature10276, doi101038ncomms4210, doi101098rspb20022104, doi101111j14209101200400741x, doi101111j1469185x201200220x, doi101666061301, openalexw2886616075"
}

Recent description of the oral cone of Anomalocaris canadensis from the Burgess Shale (Cambrian Series 3, Stage 5) highlighted significant differences from published accounts of this iconic species, and prompts a new evaluation of its morphology as a whole. All known specimens of A. canadensis, including previously unpublished material, were examined with the aim of providing a cohesive morphological description of this stem lineage arthropod. In contrast to previous descriptions, the dorsal surface of the head is shown to be covered by a small, oval carapace in close association with paired stalked eyes, and the ventral surface bears only the triradial oral cone, with no evidence of a hypostome or an anterior sclerite. The frontal appendages reveal new details of the arthrodial membranes and a narrower cross-section in dorsal view than previously reconstructed. The posterior body region reveals a complex suite of digestive, respiratory, and locomotory characters that include a differentiated foregut and hindgut, a midgut with paired glands, gill-like setal blades, and evidence of muscle bundles and struts that presumably supported the swimming movement of the body flaps. The tail fan includes a central blade in addition to the previously described three pairs of lateral blades. Some of these structures have not been identified in other anomalocaridids, making Anomalocaris critical for understanding the functional morphology of the group as a whole and corroborating its arthropod affinities.

@article{doi10166613067,
    author = "Daley, Allison C. and Edgecombe, Gregory D.",
    title = "Morphology of Anomalocaris canadensis from the Burgess Shale",
    year = "2014",
    journal = "Journal of Paleontology",
    abstract = "Recent description of the oral cone of Anomalocaris canadensis from the Burgess Shale (Cambrian Series 3, Stage 5) highlighted significant differences from published accounts of this iconic species, and prompts a new evaluation of its morphology as a whole. All known specimens of A. canadensis, including previously unpublished material, were examined with the aim of providing a cohesive morphological description of this stem lineage arthropod. In contrast to previous descriptions, the dorsal surface of the head is shown to be covered by a small, oval carapace in close association with paired stalked eyes, and the ventral surface bears only the triradial oral cone, with no evidence of a hypostome or an anterior sclerite. The frontal appendages reveal new details of the arthrodial membranes and a narrower cross-section in dorsal view than previously reconstructed. The posterior body region reveals a complex suite of digestive, respiratory, and locomotory characters that include a differentiated foregut and hindgut, a midgut with paired glands, gill-like setal blades, and evidence of muscle bundles and struts that presumably supported the swimming movement of the body flaps. The tail fan includes a central blade in addition to the previously described three pairs of lateral blades. Some of these structures have not been identified in other anomalocaridids, making Anomalocaris critical for understanding the functional morphology of the group as a whole and corroborating its arthropod affinities.",
    url = "https://doi.org/10.1666/13-067",
    doi = "10.1666/13-067",
    openalex = "W2112125066",
    references = "doi10108011035899509546213, doi101080147720192012732723, doi101098rspb20121958, doi101111j10963642200900562x, doi101111j14754983201101124x, doi101371journalpone0029233, doi101666121121, doi105281zenodo16490103"
}

@article{doi101016jearscirev201510015,
    author = "Topper, Timothy P. and Strotz, Luke C. and Holmer, Lars E. and Caron, Jean‐Bernard",
    title = "Survival on a soft seafloor: life strategies of brachiopods from the Cambrian Burgess Shale",
    year = "2015",
    journal = "Earth-Science Reviews",
    url = "https://doi.org/10.1016/j.earscirev.2015.10.015",
    doi = "10.1016/j.earscirev.2015.10.015",
    openalex = "W2203283574",
    references = "doi101016jpalaeo200902013, doi101016s0012825202001319, doi101017s0094837300003778, doi101046j14610248200300530x, doi101086283553, doi101111j14636395200500211x, doi101126science1103960, doi101126science13134091292, doi1012019781315140919, doi101214aoms1177704472, doi101371journalpone0029233, doi1018637jssv064i04, doi105479si009638011395227, doi105860choice284524"
}

Abstract The stem‐group priapulid Ottoia Walcott, 1911, is the most abundant worm in the mid‐Cambrian Burgess Shale, but has not been unambiguously demonstrated elsewhere. High‐resolution electron and optical microscopy of macroscopic Burgess Shale specimens reveals the detailed anatomy of its robust hooks, spines and pharyngeal teeth, establishing the presence of two species: Ottoia prolifica Walcott, 1911, and Ottoia tricuspida sp. nov. Direct comparison of these sclerotized elements with a suite of shale‐hosted mid‐to‐late Cambrian microfossils extends the range of ottoiid priapulids throughout the middle to upper Cambrian strata of the Western Canada Sedimentary Basin. Ottoiid priapulids represented an important component of Cambrian ecosystems: they occur in a range of lithologies and thrived in shallow water as well as in the deep‐water setting of the Burgess Shale. A wider survey of Burgess Shale macrofossils reveals specific characters that diagnose priapulid sclerites more generally, establishing the affinity of a wide range of Small Carbonaceous Fossils and demonstrating the prominent role of priapulids in Cambrian seas.

@article{doi101111pala12168,
    author = "Smith, Martin R. and Harvey, Thomas H. P. and Butterfield, Nicholas J.",
    title = "The macro‐ and microfossil record of the Cambrian priapulid Ottoia",
    year = "2015",
    journal = "Palaeontology",
    abstract = "Abstract The stem‐group priapulid Ottoia Walcott, 1911, is the most abundant worm in the mid‐Cambrian Burgess Shale, but has not been unambiguously demonstrated elsewhere. High‐resolution electron and optical microscopy of macroscopic Burgess Shale specimens reveals the detailed anatomy of its robust hooks, spines and pharyngeal teeth, establishing the presence of two species: Ottoia prolifica Walcott, 1911, and Ottoia tricuspida sp. nov. Direct comparison of these sclerotized elements with a suite of shale‐hosted mid‐to‐late Cambrian microfossils extends the range of ottoiid priapulids throughout the middle to upper Cambrian strata of the Western Canada Sedimentary Basin. Ottoiid priapulids represented an important component of Cambrian ecosystems: they occur in a range of lithologies and thrived in shallow water as well as in the deep‐water setting of the Burgess Shale. A wider survey of Burgess Shale macrofossils reveals specific characters that diagnose priapulid sclerites more generally, establishing the affinity of a wide range of Small Carbonaceous Fossils and demonstrating the prominent role of priapulids in Cambrian seas.",
    url = "https://doi.org/10.1111/pala.12168",
    doi = "10.1111/pala.12168",
    openalex = "W2128901068",
    references = "doi101016jpalaeo200705023, doi101017s000632310000548x, doi101111j1469185x1999tb00046x, doi101111j14754983200700656x, doi101126science2464928339, doi101126science28153801173, doi101130g308291, doi101130g325801, doi103140bullgeosci1280, doi105860choice416546, openalexw1573076930"
}

Recent fossil discoveries from the lower Cambrian Emu Bay Shale (EBS) on Kangaroo Island, South Australia, have provided critical insights into the tempo of the Cambrian explosion of animals, such as the origin and seemingly rapid evolution of arthropod compound eyes, as well as extending the geographical ranges of several groups to the East Gondwanan margin, supporting close faunal affinities with South China. The EBS also holds great potential for broadening knowledge on taphonomic pathways involved in the exceptional preservation of fossils in Cambrian Konservat-Lagerstätten. EBS fossils display a range of taphonomic modes for a variety of soft tissues, especially phosphatization and pyritization, in some cases recording a level of anatomical detail that is absent from most Cambrian Konservat-Lagerstätten.

@article{doi101144jgs2015083,
    author = "Paterson, John R. and García‐Bellido, Diego C. and Jago, J. B. and Gehlîng, James G. and Lee, Michael S. Y. and Edgecombe, Gregory D.",
    title = "The Emu Bay Shale Konservat-Lagerstätte: a view of Cambrian life from East Gondwana",
    year = "2015",
    journal = "Journal of the Geological Society",
    abstract = "Recent fossil discoveries from the lower Cambrian Emu Bay Shale (EBS) on Kangaroo Island, South Australia, have provided critical insights into the tempo of the Cambrian explosion of animals, such as the origin and seemingly rapid evolution of arthropod compound eyes, as well as extending the geographical ranges of several groups to the East Gondwanan margin, supporting close faunal affinities with South China. The EBS also holds great potential for broadening knowledge on taphonomic pathways involved in the exceptional preservation of fossils in Cambrian Konservat-Lagerstätten. EBS fossils display a range of taphonomic modes for a variety of soft tissues, especially phosphatization and pyritization, in some cases recording a level of anatomical detail that is absent from most Cambrian Konservat-Lagerstätten.",
    url = "https://doi.org/10.1144/jgs2015-083",
    doi = "10.1144/jgs2015-083",
    openalex = "W2174796179",
    references = "doi101007978148992427812, doi101016b9780444594259000196, doi101016jearscirev201303008, doi101016jgr200708001, doi101016jpalaeo200705023, doi101016jpalwor200610014, doi101017s1089332600002837, doi101038ncomms3485, doi101038ncomms4210, doi101073pnas1111784109, doi101073pnas1400547111, doi10108003115517908565437, doi101111j14754983200900914x, doi101130g206401, doi101130g24961a1, doi101144m382, doi10120197802031805703, doi101371journalpone0009586, doi101666050701, doi10166612056, doi101666pleo050701, doi102110palo2003p05070r, doi102110palo2009p09004r, doi104202app20100080"
}

We herein describe Surusicaris elegans gen. et sp. nov. (in Isoxyidae, amended), a middle (Series 3, Stage 5) Cambrian bivalved arthropod from the new Burgess Shale deposit of Marble Canyon (Kootenay National Park, British Columbia). Surusicaris exhibits 12 simple, partly undivided biramous trunk limbs with long tripartite caeca, which may illustrate a plesiomorphic "fused" condition of exopod and endopod. We construe also that the head is made of five somites (= four segments), including two eyes, one pair of anomalocaridid-like frontalmost appendages, and three pairs of poorly sclerotized uniramous limbs. This fossil may therefore be a candidate for illustrating the origin of the plesiomorphic head condition in euarthropods, and questions the significance of the "two-segmented head" in, e.g., fuxianhuiids. The frontalmost appendage in isoxyids is intriguingly disparate, bearing similarities with both dinocaridids and euarthropods. In order to evaluate the relative importance of bivalved arthropods, such as Surusicaris, in the hypothetical structuro-functional transition between the dinocaridid frontal appendage and the pre-oral-arguably deutocerebral-appendage of euarthropods, we chose a phenetic approach and computed morphospace occupancy for the frontalmost appendages of 36 stem and crown taxa. Results show different levels of evolutionary decoupling between frontalmost appendage disparity and body plans. Variance is greatest in dinocaridids and "stem bivalved" arthropods, but these groups do not occupy the morphospace homogeneously. Rather, the diversity of frontalmost appendages in "stem bivalved" arthropods, distinct in its absence of clear clustering, is found to link the morphologies of "short great appendages," chelicerae and antennules. This find fits the hypothesis of an increase in disparity of the deutocerebral appendage prior to its diversification in euarthropods, and possibly corresponds to its original time of development. The analysis of this pattern, however, is sensitive to the-still unclear-extent of polyphyly of the "stem bivalved" taxa.

@article{doi101371journalpone0124979,
    author = "Aria, Cédric and Caron, Jean‐Bernard",
    title = "Cephalic and Limb Anatomy of a New Isoxyid from the Burgess Shale and the Role of “Stem Bivalved Arthropods” in the Disparity of the Frontalmost Appendage",
    year = "2015",
    journal = "PLoS ONE",
    abstract = {We herein describe Surusicaris elegans gen. et sp. nov. (in Isoxyidae, amended), a middle (Series 3, Stage 5) Cambrian bivalved arthropod from the new Burgess Shale deposit of Marble Canyon (Kootenay National Park, British Columbia). Surusicaris exhibits 12 simple, partly undivided biramous trunk limbs with long tripartite caeca, which may illustrate a plesiomorphic "fused" condition of exopod and endopod. We construe also that the head is made of five somites (= four segments), including two eyes, one pair of anomalocaridid-like frontalmost appendages, and three pairs of poorly sclerotized uniramous limbs. This fossil may therefore be a candidate for illustrating the origin of the plesiomorphic head condition in euarthropods, and questions the significance of the "two-segmented head" in, e.g., fuxianhuiids. The frontalmost appendage in isoxyids is intriguingly disparate, bearing similarities with both dinocaridids and euarthropods. In order to evaluate the relative importance of bivalved arthropods, such as Surusicaris, in the hypothetical structuro-functional transition between the dinocaridid frontal appendage and the pre-oral-arguably deutocerebral-appendage of euarthropods, we chose a phenetic approach and computed morphospace occupancy for the frontalmost appendages of 36 stem and crown taxa. Results show different levels of evolutionary decoupling between frontalmost appendage disparity and body plans. Variance is greatest in dinocaridids and "stem bivalved" arthropods, but these groups do not occupy the morphospace homogeneously. Rather, the diversity of frontalmost appendages in "stem bivalved" arthropods, distinct in its absence of clear clustering, is found to link the morphologies of "short great appendages," chelicerae and antennules. This find fits the hypothesis of an increase in disparity of the deutocerebral appendage prior to its diversification in euarthropods, and possibly corresponds to its original time of development. The analysis of this pattern, however, is sensitive to the-still unclear-extent of polyphyly of the "stem bivalved" taxa.},
    url = "https://doi.org/10.1371/journal.pone.0124979",
    doi = "10.1371/journal.pone.0124979",
    openalex = "W637097716",
    references = "doi1010160016703793904512, doi10108003610917408548446, doi10108003610927408827101, doi101098rstb20140313, doi1011111475498300229, doi101146annurevecolsys281129, doi101666121121, doi1023072346830, doi1023072528823, doi1023073498751, doi104202app20090024, openalexw2242001249, openalexw2764433274, openalexw659399033"
}

The feeding ecology of the 505-million-year-old arthropod Sidneyia inexpectans from the middle Cambrian (Series 3, Stage 5) Burgess Shale fauna (British Columbia, Canada) is revealed by three lines of evidence: the structure of its digestive system, the fossilized contents of its gut and the functional anatomy of its appendages. The digestive tract of Sidneyia is straight, tubular and relatively narrow in the trunk region. It is enlarged into a pear-shaped area in the cephalic region and stretches notably to form a large pocket in the abdomen. The mouth is ventral, posteriorly directed and leads to the midgut via a short tubular structure interpreted as the oesophagus. Anteriorly, three pairs of glands with internal, branching tubular structures open into the digestive tract. These glands have equivalents in various Cambrian arthropod taxa (e.g. naraoiids) and modern arthropods. Their primary function was most likely to digest and assimilate food. The abdominal pocket of Sidneyia concentrates undigested skeletal elements and various residues. It is interpreted here as the functional analogue of the stercoral pocket of some extant terrestrial arachnids (e.g. Araneae, Solifugae), whose primary function is to store food residuals and excretory material until defecation. Analysis of the gut contents indicates that Sidneyia fed largely on small ptychopariid trilobites, brachiopods, possibly agnostids, worms and other undetermined animals. Sidneyia was primarily a durophagous carnivore with predatory and/or scavenging habits, feeding on small invertebrates that lived at the water-sediment interface. There is no evidence for selective feeding. Its food items (e.g. living prey or dead material) were grasped and manipulated ventrally by its anterior appendages, then macerated into ingestible fragments and conveyed to the mouth via the converging action of strong molar-like gnathobases. Digestion probably took place within the anterior midgut via enzymes secreted in the glands. Residues were transported through the digestive tract into the abdominal pocket. The storage of faeces suggests infrequent feeding. The early diagenetic three-dimensional preservation of the digestive glands and abdominal pocket may be due to the capacity of Sidneyia to store Phosphorus and Calcium (e.g. spherites) in its digestive tissues during life as do, for example, modern horseshoe crabs.

@article{doi101016jasd201509003,
    author = "Zacaï, Axelle and Vannier, Jean and Lerosey-Aubril, Rudy",
    title = "Reconstructing the diet of a 505-million-year-old arthropod: Sidneyia inexpectans from the Burgess Shale fauna.",
    year = "2016",
    journal = "Arthropod structure \& development",
    abstract = "The feeding ecology of the 505-million-year-old arthropod Sidneyia inexpectans from the middle Cambrian (Series 3, Stage 5) Burgess Shale fauna (British Columbia, Canada) is revealed by three lines of evidence: the structure of its digestive system, the fossilized contents of its gut and the functional anatomy of its appendages. The digestive tract of Sidneyia is straight, tubular and relatively narrow in the trunk region. It is enlarged into a pear-shaped area in the cephalic region and stretches notably to form a large pocket in the abdomen. The mouth is ventral, posteriorly directed and leads to the midgut via a short tubular structure interpreted as the oesophagus. Anteriorly, three pairs of glands with internal, branching tubular structures open into the digestive tract. These glands have equivalents in various Cambrian arthropod taxa (e.g. naraoiids) and modern arthropods. Their primary function was most likely to digest and assimilate food. The abdominal pocket of Sidneyia concentrates undigested skeletal elements and various residues. It is interpreted here as the functional analogue of the stercoral pocket of some extant terrestrial arachnids (e.g. Araneae, Solifugae), whose primary function is to store food residuals and excretory material until defecation. Analysis of the gut contents indicates that Sidneyia fed largely on small ptychopariid trilobites, brachiopods, possibly agnostids, worms and other undetermined animals. Sidneyia was primarily a durophagous carnivore with predatory and/or scavenging habits, feeding on small invertebrates that lived at the water-sediment interface. There is no evidence for selective feeding. Its food items (e.g. living prey or dead material) were grasped and manipulated ventrally by its anterior appendages, then macerated into ingestible fragments and conveyed to the mouth via the converging action of strong molar-like gnathobases. Digestion probably took place within the anterior midgut via enzymes secreted in the glands. Residues were transported through the digestive tract into the abdominal pocket. The storage of faeces suggests infrequent feeding. The early diagenetic three-dimensional preservation of the digestive glands and abdominal pocket may be due to the capacity of Sidneyia to store Phosphorus and Calcium (e.g. spherites) in its digestive tissues during life as do, for example, modern horseshoe crabs.",
    url = "https://pubmed.ncbi.nlm.nih.gov/26410799/",
    doi = "10.1016/j.asd.2015.09.003",
    pmid = "26410799"
}

was an active swimming predator of soft prey items, using its anterior appendages for food capture and manipulation, and also potentially for clinging to epibenthic substrates.

@article{doi101098rsos172206,
    author = "Vannier, Jean and Aria, Cédric and Taylor, Rod S. and Caron, Jean‐Bernard",
    title = "Waptia fieldensis Walcott, a mandibulate arthropod from the middle Cambrian Burgess Shale",
    year = "2018",
    journal = "Royal Society Open Science",
    abstract = "was an active swimming predator of soft prey items, using its anterior appendages for food capture and manipulation, and also potentially for clinging to epibenthic substrates.",
    url = "https://doi.org/10.1098/rsos.172206",
    doi = "10.1098/rsos.172206",
    openalex = "W2809290942",
    references = "doi1010079780387771014, doi101016jcub201511020, doi101038417271a, doi101038nature08742, doi101046j1525142x200202034x, doi101080106351501753462876, doi101093sysbiosys029, doi101098rspb20100590, doi1011111475498300229, doi10118617429994729, doi101186s1286201710887, doi101371journalpone0124979, doi1023073515467"
}

Burgess Shale-type (BST) fossilization of carbonaceous remains that are ordinarily lost to decay is critical to our understanding of the early evolution of complex life. Sediment composition, particularly the abundance of certain clay minerals, has been invoked as a significant factor in BST fossilization. X-ray diffraction data for 213 Cambrian shales from 19 sedimentary successions on four continents provide the first comprehensive test of the association of clay mineral assemblages with BST fossils. Samples containing BST fossils yield mineralogical compositions that form a subset within the range represented by samples containing only fossil mineralized skeletons. Logistic regression and classification tree methods reveal that BST fossils are more likely to be found in sediments rich in berthierine/chamosite and poor in celadonite and illite. This characteristic clay mineralogy probably reflects a high kaolinite/smectite ratio in the original sediment and enhanced iron availability during early diagenesis. Models derived from both methods can predict the occurrence of BST fossils in fossiliferous samples based on clay mineralogy with ~80% accuracy, providing a mineralogical signature that may be useful in refining the search for BST fossils on Earth and beyond.

@article{doi101130g399411,
    author = "Anderson, Ross P. and Tosca, Nicholas J. and Gaines, Robert R. and Koch, Nicolás Mongiardino and Briggs, Derek E. G.",
    title = "A mineralogical signature for Burgess Shale–type fossilization",
    year = "2018",
    journal = "Geology",
    abstract = "Burgess Shale-type (BST) fossilization of carbonaceous remains that are ordinarily lost to decay is critical to our understanding of the early evolution of complex life. Sediment composition, particularly the abundance of certain clay minerals, has been invoked as a significant factor in BST fossilization. X-ray diffraction data for 213 Cambrian shales from 19 sedimentary successions on four continents provide the first comprehensive test of the association of clay mineral assemblages with BST fossils. Samples containing BST fossils yield mineralogical compositions that form a subset within the range represented by samples containing only fossil mineralized skeletons. Logistic regression and classification tree methods reveal that BST fossils are more likely to be found in sediments rich in berthierine/chamosite and poor in celadonite and illite. This characteristic clay mineralogy probably reflects a high kaolinite/smectite ratio in the original sediment and enhanced iron availability during early diagenesis. Models derived from both methods can predict the occurrence of BST fossils in fossiliferous samples based on clay mineralogy with \textasciitilde 80\% accuracy, providing a mineralogical signature that may be useful in refining the search for BST fossils on Earth and beyond.",
    url = "https://doi.org/10.1130/g39941.1",
    doi = "10.1130/g39941.1",
    openalex = "W2790336912",
    references = "doi101016jpalaeo200804014, doi101017s1089332600002837"
}

The chelicerates are a ubiquitous and speciose group of animals that has a considerable ecological effect on modern terrestrial ecosystems-notably as predators of insects and also, for instance, as decomposers1. The fossil record shows that chelicerates diversified early in the marine ecosystems of the Palaeozoic era, by at least the Ordovician period2. However, the timing of chelicerate origins and the type of body plan that characterized the earliest members of this group have remained controversial. Although megacheirans3-5 have previously been interpreted as chelicerate-like, and habeliidans6 (including Sanctacaris7,8) have been suggested to belong to their immediate stem lineage, evidence for the specialized feeding appendages (chelicerae) that are diagnostic of the chelicerates has been lacking. Here we use exceptionally well-preserved and abundant fossil material from the middle Cambrian Burgess Shale (Marble Canyon, British Columbia, Canada) to show that Mollisonia plenovenatrix sp. nov. possessed robust but short chelicerae that were placed very anteriorly, between the eyes. This suggests that chelicerae evolved a specialized feeding function early on, possibly as a modification of short antennules. The head also encompasses a pair of large compound eyes, followed by three pairs of long, uniramous walking legs and three pairs of stout, gnathobasic masticatory appendages; this configuration links habeliidans with euchelicerates ('true' chelicerates, excluding the sea spiders). The trunk ends in a four-segmented pygidium and bears eleven pairs of identical limbs, each of which is composed of three broad lamellate exopod flaps, and endopods are either reduced or absent. These overlapping exopod flaps resemble euchelicerate book gills, although they lack the diagnostic operculum9. In addition, the eyes of M. plenovenatrix were innervated by three optic neuropils, which strengthens the view that a complex malacostracan-like visual system10,11 might have been plesiomorphic for all crown euarthropods. These fossils thus show that chelicerates arose alongside mandibulates12 as benthic micropredators, at the heart of the Cambrian explosion.

@article{doi101038s4158601915254,
    author = "Aria, Cédric and Caron, Jean-Bernard",
    title = "A middle Cambrian arthropod with chelicerae and proto-book gills.",
    year = "2019",
    journal = "Nature",
    abstract = "The chelicerates are a ubiquitous and speciose group of animals that has a considerable ecological effect on modern terrestrial ecosystems-notably as predators of insects and also, for instance, as decomposers1. The fossil record shows that chelicerates diversified early in the marine ecosystems of the Palaeozoic era, by at least the Ordovician period2. However, the timing of chelicerate origins and the type of body plan that characterized the earliest members of this group have remained controversial. Although megacheirans3-5 have previously been interpreted as chelicerate-like, and habeliidans6 (including Sanctacaris7,8) have been suggested to belong to their immediate stem lineage, evidence for the specialized feeding appendages (chelicerae) that are diagnostic of the chelicerates has been lacking. Here we use exceptionally well-preserved and abundant fossil material from the middle Cambrian Burgess Shale (Marble Canyon, British Columbia, Canada) to show that Mollisonia plenovenatrix sp. nov. possessed robust but short chelicerae that were placed very anteriorly, between the eyes. This suggests that chelicerae evolved a specialized feeding function early on, possibly as a modification of short antennules. The head also encompasses a pair of large compound eyes, followed by three pairs of long, uniramous walking legs and three pairs of stout, gnathobasic masticatory appendages; this configuration links habeliidans with euchelicerates ('true' chelicerates, excluding the sea spiders). The trunk ends in a four-segmented pygidium and bears eleven pairs of identical limbs, each of which is composed of three broad lamellate exopod flaps, and endopods are either reduced or absent. These overlapping exopod flaps resemble euchelicerate book gills, although they lack the diagnostic operculum9. In addition, the eyes of M. plenovenatrix were innervated by three optic neuropils, which strengthens the view that a complex malacostracan-like visual system10,11 might have been plesiomorphic for all crown euarthropods. These fossils thus show that chelicerates arose alongside mandibulates12 as benthic micropredators, at the heart of the Cambrian explosion.",
    url = "https://pubmed.ncbi.nlm.nih.gov/31511691/",
    doi = "10.1038/s41586-019-1525-4",
    openalex = "W2972754927",
    pmid = "31511691",
    references = "doi101016jasd201507005, doi101038nature09038, doi101038nature11495, doi101038nature20804, doi101038ncomms4210, doi101073pnas1819366116, doi101080106351501753462876, doi101093sysbiosys029, doi101098rsos172206, doi101111j14754983201101124x, doi101130g24961a1, doi101186s1286201710887, openalexw645459046"
}

Radiodonts, a clade of Cambro-Devonian stem group euarthropods, have classically been regarded as nektonic apex predators. However, many aspects of radiodont morphology and ecology have remained unclear because of the typically fragmentary nature of fossil material. Here, we describe a new hurdiid radiodont based on abundant and exceptionally well-preserved fossils from the Burgess Shale (Marble Canyon area, British Columbia, Canada). Cambroraster falcatus gen. et sp. nov. is characterized by an extra-large horseshoe-shaped head carapace, bearing conspicuous posterolateral spinous processes, and partially covering a short trunk with eight pairs of lateral flaps. Each of the pair of frontal appendages possess five mesially curving rake-like endites equipped with a series of anteriorly directed hooked spines, altogether surrounding the oral cone. This feeding apparatus suggests a micro to macrophagous sediment-sifting feeding ecology. Cambroraster illuminates the evolution of Hurdiidae and evinces the exploitation of the diversifying infauna by these large and specialized nektobenthic carnivores in the aftermath of the Cambrian explosion.

@article{doi101098rspb20191079,
    author = "Moysiuk, J. and Caron, Jean‐Bernard",
    title = "A new hurdiid radiodont from the Burgess Shale evinces the exploitation of Cambrian infaunal food sources",
    year = "2019",
    journal = "Proceedings of the Royal Society B Biological Sciences",
    abstract = "Radiodonts, a clade of Cambro-Devonian stem group euarthropods, have classically been regarded as nektonic apex predators. However, many aspects of radiodont morphology and ecology have remained unclear because of the typically fragmentary nature of fossil material. Here, we describe a new hurdiid radiodont based on abundant and exceptionally well-preserved fossils from the Burgess Shale (Marble Canyon area, British Columbia, Canada). Cambroraster falcatus gen. et sp. nov. is characterized by an extra-large horseshoe-shaped head carapace, bearing conspicuous posterolateral spinous processes, and partially covering a short trunk with eight pairs of lateral flaps. Each of the pair of frontal appendages possess five mesially curving rake-like endites equipped with a series of anteriorly directed hooked spines, altogether surrounding the oral cone. This feeding apparatus suggests a micro to macrophagous sediment-sifting feeding ecology. Cambroraster illuminates the evolution of Hurdiidae and evinces the exploitation of the diversifying infauna by these large and specialized nektobenthic carnivores in the aftermath of the Cambrian explosion.",
    url = "https://doi.org/10.1098/rspb.2019.1079",
    doi = "10.1098/rspb.2019.1079",
    openalex = "W2965739174",
    references = "doi101038nature13486, doi101038nature14256, doi101038s415590160022, doi101080106351501753462876, doi101080147720192012732723, doi101093molbevmsu300, doi101093sysbiosys029, doi1011111475498300080, doi101111j10960031200700161x, doi101126science1169514, doi101371journalpone0124979, doi105860choice420301, openalexw2611511275"
}

Recent investigations on neurological tissues preserved in Cambrian fossils have clarified the phylogenetic affinities and head segmentation in pivotal members of stem-group Euarthropoda. However, palaeoneuroanatomical features are often incomplete or described from single exceptional specimens, raising concerns about the morphological interpretation of fossilized neurological structures and their significance for early euarthropod evolution. Here, we describe the central nervous system (CNS) of the short great-appendage euarthropod Alalcomenaeus based on material from two Cambrian Burgess Shale-type deposits of the American Great Basin, the Pioche Formation (Stage 4) and the Marjum Formation (Drumian). The specimens reveal complementary ventral and lateral views of the CNS, preserved as a dark carbonaceous compression throughout the body. The head features a dorsal brain connected to four stalked ventral eyes, and four pairs of segmental nerves. The first to seventh trunk tergites overlie a ventral nerve cord with seven ganglia, each associated with paired sets of segmental nerve bundles. Posteriorly, the nerve cord features elongate thread-like connectives. The Great Basin fossils strengthen the original description-and broader evolutionary implications-of the CNS in Alalcomenaeus from the early Cambrian (Stage 3) Chengjiang deposit of South China. The spatio-temporal recurrence of fossilized neural tissues in Cambrian Konservat-Lagerstätten across North America (Pioche, Burgess Shale, Marjum) and South China (Chengjiang, Xiaoshiba) indicates that their preservation is consistent with the mechanism of Burgess Shale-type fossilization, without the need to invoke alternative taphonomic pathways or the presence of microbial biofilms.

@article{doi101098rspb20192370,
    author = "Ortega‐Hernández, Javier and Lerosey‐Aubril, Rudy and Pates, Stephen",
    title = "Proclivity of nervous system preservation in Cambrian Burgess Shale-type deposits",
    year = "2019",
    journal = "Proceedings of the Royal Society B Biological Sciences",
    abstract = "Recent investigations on neurological tissues preserved in Cambrian fossils have clarified the phylogenetic affinities and head segmentation in pivotal members of stem-group Euarthropoda. However, palaeoneuroanatomical features are often incomplete or described from single exceptional specimens, raising concerns about the morphological interpretation of fossilized neurological structures and their significance for early euarthropod evolution. Here, we describe the central nervous system (CNS) of the short great-appendage euarthropod Alalcomenaeus based on material from two Cambrian Burgess Shale-type deposits of the American Great Basin, the Pioche Formation (Stage 4) and the Marjum Formation (Drumian). The specimens reveal complementary ventral and lateral views of the CNS, preserved as a dark carbonaceous compression throughout the body. The head features a dorsal brain connected to four stalked ventral eyes, and four pairs of segmental nerves. The first to seventh trunk tergites overlie a ventral nerve cord with seven ganglia, each associated with paired sets of segmental nerve bundles. Posteriorly, the nerve cord features elongate thread-like connectives. The Great Basin fossils strengthen the original description-and broader evolutionary implications-of the CNS in Alalcomenaeus from the early Cambrian (Stage 3) Chengjiang deposit of South China. The spatio-temporal recurrence of fossilized neural tissues in Cambrian Konservat-Lagerstätten across North America (Pioche, Burgess Shale, Marjum) and South China (Chengjiang, Xiaoshiba) indicates that their preservation is consistent with the mechanism of Burgess Shale-type fossilization, without the need to invoke alternative taphonomic pathways or the presence of microbial biofilms.",
    url = "https://doi.org/10.1098/rspb.2019.2370",
    doi = "10.1098/rspb.2019.2370",
    openalex = "W2994943484",
    references = "briggs2003the, doi101038nature10689, doi101038nature11495, doi101038nature13486, doi10108000241160410004764, doi101098rsos172206, doi101098rstb20140313, doi101111j14754983200700656x, doi101111j150239311995tb01587x, doi101126scienceaau8800, doi1016660094837320020280155lgatio20co2, openalexw2138270429"
}

Burgess Shale-type fossil Lagerstätten provide the best evidence for deciphering the biotic patterns and magnitude of the Cambrian explosion. Here, we report a Lagerstätte from South China, the Qingjiang biota (~518 million years old), which is dominated by soft-bodied taxa from a distal shelf setting. The Qingjiang biota is distinguished by pristine carbonaceous preservation of labile organic features, a very high proportion of new taxa (~53%), and preliminary taxonomic diversity that suggests it could rival the Chengjiang and Burgess Shale biotas. Defining aspects of the Qingjiang biota include a high abundance of cnidarians, including both medusoid and polypoid forms; new taxa resembling extant kinorhynchs; and abundant larval or juvenile forms. This distinctive composition holds promise for providing insights into the evolution of Cambrian ecosystems across environmental gradients.

@article{doi101126scienceaau8800,
    author = "Fu, Dongjing and Tong, Guanghui and Dai, Tao and Liu, Wei and Yang, Yuning and Zhang, Yuan and Cui, Linhao and Li, Luoyang and Yun, Hao and Wu, Yu and Sun, Ao and Liu, Cong and Pei, Wenrui and Gaines, Robert R. and Zhang, Xingliang",
    title = "The Qingjiang biota—A Burgess Shale–type fossil Lagerstätte from the early Cambrian of South China",
    year = "2019",
    journal = "Science",
    abstract = "Burgess Shale-type fossil Lagerstätten provide the best evidence for deciphering the biotic patterns and magnitude of the Cambrian explosion. Here, we report a Lagerstätte from South China, the Qingjiang biota (\textasciitilde 518 million years old), which is dominated by soft-bodied taxa from a distal shelf setting. The Qingjiang biota is distinguished by pristine carbonaceous preservation of labile organic features, a very high proportion of new taxa (\textasciitilde 53\%), and preliminary taxonomic diversity that suggests it could rival the Chengjiang and Burgess Shale biotas. Defining aspects of the Qingjiang biota include a high abundance of cnidarians, including both medusoid and polypoid forms; new taxa resembling extant kinorhynchs; and abundant larval or juvenile forms. This distinctive composition holds promise for providing insights into the evolution of Cambrian ecosystems across environmental gradients.",
    url = "https://doi.org/10.1126/science.aau8800",
    doi = "10.1126/science.aau8800",
    openalex = "W2923733494",
    references = "doi1010029781118896372, doi101007s114340140419y, doi1010160016703795000382, doi101016b9780444594259000196, doi101016jearscirev201707017, doi101016jpalwor201510001, doi101017s108933260000276x, doi101038nature11874, doi101038ncomms4210, doi101073pnas1111784109, doi101073pnas1719962115, doi101111j14754983200700656x, doi101130g24961a1, doi101144jgs1582211, doi101144jgs2015083, doi10166612056, doi102110palo2009p09004r"
}

We report the Fandian biota, a new Konservat-Lagerstätte from the Cambrian Stage 3 Yuxiansi and Jiulaodong Formations in Sichuan, South China, with close faunal links to the Chengjiang biota in Yunnan. The biodiversity of the Fandian biota includes total-group euarthropods (radiodonts, bivalved forms, acercostracans, trilobites, non-biomineralized trilobitomorphs), armoured lobopodians, palaeoscolecids, pedunculate brachiopods, hyoliths, chancelloriids, sponges, and filamentous algae. Benthic dwellers dominate the fossil community (e.g. trilobitomorphs, brachiopods, sponges), with rare instances of nektonic (radiodonts, bivalved euarthropods) and infaunal (palaeoscolecids) organisms. The Fandian biota contains soft-bodied taxa that were only known from Chengjiang and Xiaoshiba until now, namely Primicaris (acercostracan), Xandarella (non-trilobite trilobitomorph) and Mafangscolex (palaeoscolecid), expanding the distribution of these previously endemic taxa beyond Yunnan to the northern Yangtze Platform during the Cambrian Stage 3. Our findings provide a more comprehensive understanding of early Cambrian biodiversity that inhabited the Yangtze Platform over a substantially greater palaeobiogeographic distribution than previously considered.

@article{doi101016jearscirev2020103409,
    author = "Du, Kun‐sheng and Ortega‐Hernández, Javier and Yang, Jie and Yang, X. C. and Guo, Qing-hao and Li, Wei and He, Ji-feng and Li, Ke-ren and Du, Jialin and Hou, Jin‐bo and Zhang, Xiguang",
    title = "A new early Cambrian Konservat-Lagerstätte expands the occurrence of Burgess Shale-type deposits on the Yangtze Platform",
    year = "2020",
    journal = "Earth-Science Reviews",
    abstract = "We report the Fandian biota, a new Konservat-Lagerstätte from the Cambrian Stage 3 Yuxiansi and Jiulaodong Formations in Sichuan, South China, with close faunal links to the Chengjiang biota in Yunnan. The biodiversity of the Fandian biota includes total-group euarthropods (radiodonts, bivalved forms, acercostracans, trilobites, non-biomineralized trilobitomorphs), armoured lobopodians, palaeoscolecids, pedunculate brachiopods, hyoliths, chancelloriids, sponges, and filamentous algae. Benthic dwellers dominate the fossil community (e.g. trilobitomorphs, brachiopods, sponges), with rare instances of nektonic (radiodonts, bivalved euarthropods) and infaunal (palaeoscolecids) organisms. The Fandian biota contains soft-bodied taxa that were only known from Chengjiang and Xiaoshiba until now, namely Primicaris (acercostracan), Xandarella (non-trilobite trilobitomorph) and Mafangscolex (palaeoscolecid), expanding the distribution of these previously endemic taxa beyond Yunnan to the northern Yangtze Platform during the Cambrian Stage 3. Our findings provide a more comprehensive understanding of early Cambrian biodiversity that inhabited the Yangtze Platform over a substantially greater palaeobiogeographic distribution than previously considered.",
    url = "https://doi.org/10.1016/j.earscirev.2020.103409",
    doi = "10.1016/j.earscirev.2020.103409",
    openalex = "W3093022371",
    references = "doi101144jgs2019043"
}

Abstract The middle (Wuliuan Stage) Cambrian Burgess Shale is famous for its exceptional preservation of diverse and abundant soft-bodied animals through the “thick” Stephen Formation. However, with the exception of the Walcott Quarry (Fossil Ridge) and the stratigraphically older Tulip Beds (Mount Stephen), which are both in Yoho National Park (British Columbia), quantitative assessments of the Burgess Shale have remained limited. Here we first provide a detailed quantitative overview of the diversity and structure of the Marble Canyon Burgess Shale locality based on 16,438 specimens. Located 40 km southeast of the Walcott Quarry in Kootenay National Park (British Columbia), Marble Canyon represents the youngest site of the “thick” Stephen Formation. We then combine paleoecological data sets from Marble Canyon, Walcott Quarry, Tulip Beds, and Raymond Quarry, which lies approximately 20 m directly above the Walcott Quarry, to yield a combined species abundance data set of 77,179 specimens encompassing 234 species-level taxa. Marble Canyon shows significant temporal changes in both taxonomic and ecological groups, suggesting periods of stasis followed by rapid turnover patterns at local and short temporal scales. At wider geographic and temporal scales, the different Burgess Shale sites occupy distinct areas in multivariate space. Overall, this suggests that the Burgess Shale paleocommunity is far patchier than previously thought and varies at both local and regional scales through the “thick” Stephen Formation. This underscores that our understanding of Cambrian diversity and ecological networks, particularly in early animal ecosystems, remains limited and highly dependent on new discoveries.

@article{doi101017pab201942,
    author = "Nanglu, Karma and Caron, Jean‐Bernard and Gaines, Robert R.",
    title = "The Burgess Shale paleocommunity with new insights from Marble Canyon, British Columbia",
    year = "2020",
    journal = "Paleobiology",
    abstract = "Abstract The middle (Wuliuan Stage) Cambrian Burgess Shale is famous for its exceptional preservation of diverse and abundant soft-bodied animals through the “thick” Stephen Formation. However, with the exception of the Walcott Quarry (Fossil Ridge) and the stratigraphically older Tulip Beds (Mount Stephen), which are both in Yoho National Park (British Columbia), quantitative assessments of the Burgess Shale have remained limited. Here we first provide a detailed quantitative overview of the diversity and structure of the Marble Canyon Burgess Shale locality based on 16,438 specimens. Located 40 km southeast of the Walcott Quarry in Kootenay National Park (British Columbia), Marble Canyon represents the youngest site of the “thick” Stephen Formation. We then combine paleoecological data sets from Marble Canyon, Walcott Quarry, Tulip Beds, and Raymond Quarry, which lies approximately 20 m directly above the Walcott Quarry, to yield a combined species abundance data set of 77,179 specimens encompassing 234 species-level taxa. Marble Canyon shows significant temporal changes in both taxonomic and ecological groups, suggesting periods of stasis followed by rapid turnover patterns at local and short temporal scales. At wider geographic and temporal scales, the different Burgess Shale sites occupy distinct areas in multivariate space. Overall, this suggests that the Burgess Shale paleocommunity is far patchier than previously thought and varies at both local and regional scales through the “thick” Stephen Formation. This underscores that our understanding of Cambrian diversity and ecological networks, particularly in early animal ecosystems, remains limited and highly dependent on new discoveries.",
    url = "https://doi.org/10.1017/pab.2019.42",
    doi = "10.1017/pab.2019.42",
    openalex = "W3008824536",
    references = "doi101016jpalwor200610005, doi101017cbo9780511623332, doi101017s1089332600002837, doi101038nature13414, doi101038ncomms4210, doi101038s4158601915254, doi101111j14429993200501502x, doi101111j14610248200500871x, doi101126science13134091292, doi101146annureves15110184002033, doi101186s1291501602714, doi101371journalpone0029233, doi101371journalpone0052200, doi101371journalpone0124979, doi10166612056, doi1018900012965820020831771tuntob20co2, doi102110palo2003p05070r, doi1023071931600, doi1023071933500, doi1023073071998, doi105860choice421547"
}

Abstract The role of minerals in Burgess Shale–type fossilization is controversial, particularly that of the clay mineral kaolinite. Kaolinite may have formed on carcasses or attached to them as they decayed, stabilizing organic matter. Alternatively, kaolinite may have formed during metamorphism, playing no role in the preservation of soft tissues. Evaluating the formation and taphonomic role of kaolinite is difficult, because the mineralogy of Burgess Shale–type fossils is incompletely known. We used in situ selected-area X-ray diffraction to constrain the mineralogy of fossils from the classic Burgess Shale Formation in British Columbia, Canada. Fossils can be distinguished from the matrix that surrounds them by the presence of dolomite, kaolinite, and pyrite. Chlorite may be more abundant in the matrix. The preferential survival of kaolinite in association with fossils provides evidence of early diagenetic clay-organic interactions that protected the clay from metamorphic transformation. Kaolinite likely played a crucial role in fossilization, inhibiting the growth of heterotrophic bacteria and aiding polymerization of soft tissue biomolecules. This may result in biases in soft-tissue preservation to areas and times where kaolinite was prevalent.

@article{doi101130g480671,
    author = "Anderson, Ross P. and Tosca, Nicholas J. and Saupe, Erin E. and Wade, Jon and Briggs, Derek E. G.",
    title = "Early formation and taphonomic significance of kaolinite associated with Burgess Shale fossils",
    year = "2020",
    journal = "Geology",
    abstract = "Abstract The role of minerals in Burgess Shale–type fossilization is controversial, particularly that of the clay mineral kaolinite. Kaolinite may have formed on carcasses or attached to them as they decayed, stabilizing organic matter. Alternatively, kaolinite may have formed during metamorphism, playing no role in the preservation of soft tissues. Evaluating the formation and taphonomic role of kaolinite is difficult, because the mineralogy of Burgess Shale–type fossils is incompletely known. We used in situ selected-area X-ray diffraction to constrain the mineralogy of fossils from the classic Burgess Shale Formation in British Columbia, Canada. Fossils can be distinguished from the matrix that surrounds them by the presence of dolomite, kaolinite, and pyrite. Chlorite may be more abundant in the matrix. The preferential survival of kaolinite in association with fossils provides evidence of early diagenetic clay-organic interactions that protected the clay from metamorphic transformation. Kaolinite likely played a crucial role in fossilization, inhibiting the growth of heterotrophic bacteria and aiding polymerization of soft tissue biomolecules. This may result in biases in soft-tissue preservation to areas and times where kaolinite was prevalent.",
    url = "https://doi.org/10.1130/g48067.1",
    doi = "10.1130/g48067.1",
    openalex = "W3139465945",
    references = "doi101016jpalaeo200804014, doi101017s1089332600002837"
}

The geologically rapid appearance of fossils of modern animal phyla within Cambrian strata is a defining characteristic of the history of life on Earth. However, temporal calibration of the base of the Cambrian Period remains uncertain within millions of years, which has resulted in mounting challenges to the concept of a discrete Cambrian explosion. We present precise zircon U-Pb dates for the lower Wood Canyon Formation, Nevada. These data demonstrate the base of the Cambrian Period, as defined by both ichnofossil biostratigraphy and carbon isotope chemostratigraphy, was younger than 533 Mya, at least 6 My later than currently recognized. This new geochronology condenses previous age models for the Nemakit-Daldynian (early Cambrian) and, integrated with global records, demonstrates an explosive tempo to the early radiation of modern animal phyla.

@article{doi101073pnas2301478120,
    author = "Nelson, Lyle L. and Crowley, James L. and Smith, Emily F. and Schwartz, Darin and Hodgin, Eben B. and Schmitz, Mark D.",
    title = "Cambrian explosion condensed: High-precision geochronology of the lower Wood Canyon Formation, Nevada",
    year = "2023",
    journal = "Proceedings of the National Academy of Sciences",
    abstract = "The geologically rapid appearance of fossils of modern animal phyla within Cambrian strata is a defining characteristic of the history of life on Earth. However, temporal calibration of the base of the Cambrian Period remains uncertain within millions of years, which has resulted in mounting challenges to the concept of a discrete Cambrian explosion. We present precise zircon U-Pb dates for the lower Wood Canyon Formation, Nevada. These data demonstrate the base of the Cambrian Period, as defined by both ichnofossil biostratigraphy and carbon isotope chemostratigraphy, was younger than 533 Mya, at least 6 My later than currently recognized. This new geochronology condenses previous age models for the Nemakit-Daldynian (early Cambrian) and, integrated with global records, demonstrates an explosive tempo to the early radiation of modern animal phyla.",
    url = "https://doi.org/10.1073/pnas.2301478120",
    doi = "10.1073/pnas.2301478120",
    openalex = "W4384499690",
    references = "doi101016b978012824360200019x, doi102110sedred200314, doi103133pp620"
}

The Cambrian Explosion is often seen as a singular event requiring an explanation. In fact, it is better represented as a cascade of linked events, each with numerous causes. The iconic middle Cambrian fauna, represented by sites such as the Burgess Shale, is a culmination of several phases of increases in taxonomic diversity and morphological complexity. I focus on an often-overlooked increase in complexity that took place in a limited number of phyla in parallel after the main "explosion". This increase in morphological complexity and disparity was facilitated by an increase in the complexity of the central nervous system, which in itself was a selective response to the ecological complexity of the biosphere, which had been increasing from the late Ediacaran. Genetic regulatory components that contributed to an increasingly differentiated and regionalized central nervous system were developmentally co-opted to increase the differentiation and complexity of additional organ systems. This process took place convergently in arthropods, mollusks, and annelids at different times throughout the Cambrian and, later in the Ordovician, also in vertebrates.

@article{doi101002bies70136,
    author = "Chipman, Ariel D",
    title = "An Increase in Animal Diversity was Facilitated by Ecologically-Driven Brain Complexity Throughout the Cambrian.",
    year = "2026",
    journal = "BioEssays: news and reviews in molecular, cellular and developmental biology",
    abstract = {The Cambrian Explosion is often seen as a singular event requiring an explanation. In fact, it is better represented as a cascade of linked events, each with numerous causes. The iconic middle Cambrian fauna, represented by sites such as the Burgess Shale, is a culmination of several phases of increases in taxonomic diversity and morphological complexity. I focus on an often-overlooked increase in complexity that took place in a limited number of phyla in parallel after the main "explosion". This increase in morphological complexity and disparity was facilitated by an increase in the complexity of the central nervous system, which in itself was a selective response to the ecological complexity of the biosphere, which had been increasing from the late Ediacaran. Genetic regulatory components that contributed to an increasingly differentiated and regionalized central nervous system were developmentally co-opted to increase the differentiation and complexity of additional organ systems. This process took place convergently in arthropods, mollusks, and annelids at different times throughout the Cambrian and, later in the Ordovician, also in vertebrates.},
    url = "https://pmc.ncbi.nlm.nih.gov/articles/PMC13088219/",
    doi = "10.1002/bies.70136",
    pmcid = "PMC13088219",
    pmid = "41994957"
}

Unambiguous body fossils of annelids (ringed worms) first appear in the Cambrian Period but are so far known exclusively as flattened specimens preserved in Burgess Shale-type Lagerstätten. Here, we report phosphatized microfossils, interpreted as polychaete annelids, from a distinct taphonomic window (i.e., three-dimensional Orsten-type preservation) in the earliest Cambrian (early Fortunian Age, ca. 535 Ma) Zhangjiagou Lagerstätte of South China. The fossils are millimetric in length and preserved as three-dimensional endocasts of the body. They exhibit clear trunk segmentation, with each segment bearing a pair of lateral or ventrolateral outgrowths. Two species, Kuanchuanpivermis brevicruris gen. et sp. nov. and Zhangjiagoivermis longicruris gen. et sp. nov., are distinguished based on the relative length of these outgrowths. The lateral outgrowths terminate in a bifurcation into two lobes of equal, subequal, or unequal size, closely resembling the notopodium and neuropodium of annelid parapodia. Both species are interpreted as members of the total-group Annelida. Kuanchuanpivermis brevicruris has relatively short appendages and may have been a benthic annelid similar to modern nereids. Zhangjiagoivermis longicruris closely resembles fossil and extant polychaetes (e.g., Eotomopteris and Tomopteris) in their relatively long appendages, suggesting a swimming lifestyle and representing the earliest known semi-pelagic annelid. These findings indicate that annelids had already acquired a polychaete-like body plan in the Fortunian and that early members of the clade had diverged from their living sister group and differentiated into forms with both short and elongate parapodia by the Fortunian Age.

@article{doi101073pnas2538071123,
    author = "Xian, Xiaofeng and Zhang, Huaqiao and Xiao, Shuhai and Waloszek, Dieter and Maas, Andreas and Duan, Baichuan",
    title = "Polychaete annelids from the earliest Cambrian Period.",
    year = "2026",
    journal = "Proceedings of the National Academy of Sciences of the United States of America",
    abstract = "Unambiguous body fossils of annelids (ringed worms) first appear in the Cambrian Period but are so far known exclusively as flattened specimens preserved in Burgess Shale-type Lagerstätten. Here, we report phosphatized microfossils, interpreted as polychaete annelids, from a distinct taphonomic window (i.e., three-dimensional Orsten-type preservation) in the earliest Cambrian (early Fortunian Age, ca. 535 Ma) Zhangjiagou Lagerstätte of South China. The fossils are millimetric in length and preserved as three-dimensional endocasts of the body. They exhibit clear trunk segmentation, with each segment bearing a pair of lateral or ventrolateral outgrowths. Two species, Kuanchuanpivermis brevicruris gen. et sp. nov. and Zhangjiagoivermis longicruris gen. et sp. nov., are distinguished based on the relative length of these outgrowths. The lateral outgrowths terminate in a bifurcation into two lobes of equal, subequal, or unequal size, closely resembling the notopodium and neuropodium of annelid parapodia. Both species are interpreted as members of the total-group Annelida. Kuanchuanpivermis brevicruris has relatively short appendages and may have been a benthic annelid similar to modern nereids. Zhangjiagoivermis longicruris closely resembles fossil and extant polychaetes (e.g., Eotomopteris and Tomopteris) in their relatively long appendages, suggesting a swimming lifestyle and representing the earliest known semi-pelagic annelid. These findings indicate that annelids had already acquired a polychaete-like body plan in the Fortunian and that early members of the clade had diverged from their living sister group and differentiated into forms with both short and elongate parapodia by the Fortunian Age.",
    url = "https://pubmed.ncbi.nlm.nih.gov/42008710/",
    doi = "10.1073/pnas.2538071123",
    pmid = "42008710"
}

This study investigates the microstructure and biomechanics of the Wuliuan phosphatic brachiopods Iberotreta sampelayoi and Genetreta trilix from the Láncara Formation in northern Spain. Both taxa share the characteristic stacked columnar shell architecture of early linguliforms, yet quantitative analyses reveal marked differences in microcolumn geometry. Iberotreta possesses small, densely packed and highly regulated columns, whereas Genetreta develops larger, more heterogeneous columns with weaker geometric constraint. Statistical comparisons show that all column dimensions differ significantly between species, and allometric analyses indicate tightly coordinated growth in Iberotreta versus a less constrained pattern in Genetreta, consistent with greater sensitivity to local physiological or environmental conditions. Biomechanical modelling demonstrates that these disparities correspond to contrasting functional strategies: G. trilix withstands higher stresses, particularly in the lateral middle region, while I. sampelayoi maintains stiffness with reduced mineral investment, producing a lightweight and energetically efficient shell. Comparisons with extant brachiopods support a functional link between shell microstructure and biomechanical performance. Together, our results demonstrate that variation in column size, organization and allometry served as an adaptive axis in early phosphatic brachiopods, showing that micrometre-scale skeletal architecture played a central role in shaping the ecological complexity of Cambrian benthic communities during the early Cambrian.

@article{doi101098rspb20260192,
    author = "Esteve, Jorge and González-Cloquells, Alejandro and Arriola, Antonio",
    title = "Microstructural biomechanics underpin Cambrian phosphatic brachiopod diversification.",
    year = "2026",
    journal = "Proceedings. Biological sciences",
    abstract = "This study investigates the microstructure and biomechanics of the Wuliuan phosphatic brachiopods Iberotreta sampelayoi and Genetreta trilix from the Láncara Formation in northern Spain. Both taxa share the characteristic stacked columnar shell architecture of early linguliforms, yet quantitative analyses reveal marked differences in microcolumn geometry. Iberotreta possesses small, densely packed and highly regulated columns, whereas Genetreta develops larger, more heterogeneous columns with weaker geometric constraint. Statistical comparisons show that all column dimensions differ significantly between species, and allometric analyses indicate tightly coordinated growth in Iberotreta versus a less constrained pattern in Genetreta, consistent with greater sensitivity to local physiological or environmental conditions. Biomechanical modelling demonstrates that these disparities correspond to contrasting functional strategies: G. trilix withstands higher stresses, particularly in the lateral middle region, while I. sampelayoi maintains stiffness with reduced mineral investment, producing a lightweight and energetically efficient shell. Comparisons with extant brachiopods support a functional link between shell microstructure and biomechanical performance. Together, our results demonstrate that variation in column size, organization and allometry served as an adaptive axis in early phosphatic brachiopods, showing that micrometre-scale skeletal architecture played a central role in shaping the ecological complexity of Cambrian benthic communities during the early Cambrian.",
    url = "https://pubmed.ncbi.nlm.nih.gov/41980737/",
    doi = "10.1098/rspb.2026.0192",
    pmid = "41980737"
}

The late Neoproterozoic-early Paleozoic (~600 to 520 million years ago) witnessed a fundamental shift under atmosphere-ocean redox conditions, where pulsed ocean oxygenation events (OOEs) were replaced by episodic ocean anoxic events (OAEs). The Cambrian Steptoean positive carbon isotope excursion (SPICE) event (494.5 to 492.5 million years ago) represents a major early Paleozoic OAE, yet its drivers and underlying dynamics remain controversial. Here, we present carbonate uranium isotope (δ238Ucarb) data from North and South China, revealing a sharp decrease from -0.29 ± 0.12 per mil to -0.85 ± 0.03 per mil at the onset of the SPICE event, followed by a return to pre-excursion values. This indicates a rapid onset of global ocean anoxia before the rise of δ13Ccarb values, followed by a transition to oxic conditions. Integrating δ238Ucarb data with refined COPSE (Carbon, Oxygen, Phosphorus, Sulphur, and Evolution) biogeochemical modeling reconciles the pre-SPICE redox paradox of low atmospheric pO2 coexisting with limited seafloor anoxia. We propose that the SPICE and its associated excursions reflect a non-steady-state Earth system behavior, involving oscillations in coupled phosphorus-oxygen-carbon-sulfur and uranium cycles, which influenced the evolution of early animals through redox-dependent biodiversity filters.

@article{doi101126sciadvaeb9224,
    author = "Sheng, Kai and Li, Zi-Heng and Zhou, Jian-Lin and Lin, Yi-Bo and Xiong, Guo-Lin and Ren, Guang-Ying and Chen, Zhong-Qiang and Lenton, Timothy M and Shen, Shu-Zhong and Zhang, Feifei",
    title = "Earth system instability explains redox paradox during late Cambrian SPICE event.",
    year = "2026",
    journal = "Science advances",
    abstract = "The late Neoproterozoic-early Paleozoic (\textasciitilde 600 to 520 million years ago) witnessed a fundamental shift under atmosphere-ocean redox conditions, where pulsed ocean oxygenation events (OOEs) were replaced by episodic ocean anoxic events (OAEs). The Cambrian Steptoean positive carbon isotope excursion (SPICE) event (494.5 to 492.5 million years ago) represents a major early Paleozoic OAE, yet its drivers and underlying dynamics remain controversial. Here, we present carbonate uranium isotope (δ238Ucarb) data from North and South China, revealing a sharp decrease from -0.29 ± 0.12 per mil to -0.85 ± 0.03 per mil at the onset of the SPICE event, followed by a return to pre-excursion values. This indicates a rapid onset of global ocean anoxia before the rise of δ13Ccarb values, followed by a transition to oxic conditions. Integrating δ238Ucarb data with refined COPSE (Carbon, Oxygen, Phosphorus, Sulphur, and Evolution) biogeochemical modeling reconciles the pre-SPICE redox paradox of low atmospheric pO2 coexisting with limited seafloor anoxia. We propose that the SPICE and its associated excursions reflect a non-steady-state Earth system behavior, involving oscillations in coupled phosphorus-oxygen-carbon-sulfur and uranium cycles, which influenced the evolution of early animals through redox-dependent biodiversity filters.",
    url = "https://pmc.ncbi.nlm.nih.gov/articles/PMC13068071/",
    doi = "10.1126/sciadv.aeb9224",
    pmcid = "PMC13068071",
    pmid = "41961931"
}