Arthropods

@misc{moore1959protarthropoda16,
    author = "Moore, R. C",
    title = "Protarthropoda",
    year = "1959",
    howpublished = "p. O16-O20, in Moore, R. C., ed., Treatise on Invertebrate Paleontology, Part O: p. O1-O560",
    note = "talkorigins\_source = {true}; raw\_reference = {Moore, R. C., 1959, Protarthropoda: p. O16-O20, in Moore, R. C., ed., Treatise on Invertebrate Paleontology, Part O: p. O1-O560.}"
}

@misc{strmer1959trilobitoidea20,
    author = "Strmer, L",
    title = "Trilobitoidea, in Moore, R. C., ed., Treatise on Invertebrate Paleontology, Part O, Arthropoda I",
    year = "1959",
    howpublished = "p. 23-37",
    note = "talkorigins\_source = {true}; raw\_reference = {Strmer, L., 1959, Trilobitoidea, in Moore, R. C., ed., Treatise on Invertebrate Paleontology, Part O, Arthropoda I: p. 23-37.}"
}

(Uploaded by Plazi from the Biodiversity Heritage Library) No abstract provided.

@article{doi105281zenodo16273729,
    author = "Rolfe, William David Ian",
    title = "Two new arthropod carapaces from the Burgess Shale (Middle Cambrian) of Canada",
    year = "1962",
    journal = "Biodiversity Heritage Library (Smithsonian Institution)",
    abstract = "(Uploaded by Plazi from the Biodiversity Heritage Library) No abstract provided.",
    url = "https://doi.org/10.5281/zenodo.16273729",
    doi = "10.5281/zenodo.16273729",
    openalex = "W2991741276"
}

@incollection{crow1964arthropods,
    author = "CROW, W.B.",
    title = "ARTHROPODS",
    year = "1964",
    booktitle = "A Synopsis of Biology",
    url = "https://doi.org/10.1016/b978-1-4831-6826-5.50044-3",
    doi = "10.1016/b978-1-4831-6826-5.50044-3",
    pages = "285-298"
}

Fossils were collected from the Wheeler and Marjum Formations (1,400-1,800 ft limestone and shale), from six measured sections in the House Range and one in Drum Mountains and from other localities in western Utah. Trilobites (43 species), brachiopods (eight species), mollusks (four species), and sponges (two species) are described. Three genera (Trymataspis, Utagnostus, Utaspis) and 21 species of trilobites are new. Abundant silicified specimens provide new information on morphology and ontogeny of agnostid trilobites. Evolutionary trends within Agnostidae and other families are discussed. The trilobites belong to the Bolaspidella Assemblage Zone of the standard North American Cambrian; three local assemblage subzones are named Bathyuriscus fimbriatus, Bolaspidella contracta, and Lejopyge calva.

@article{openalexw2413383410,
    author = "Robison, Richard A.",
    title = "Late Middle Cambrian faunas from western Utah",
    year = "1964",
    journal = "Journal of Paleontology",
    abstract = "Fossils were collected from the Wheeler and Marjum Formations (1,400-1,800 ft limestone and shale), from six measured sections in the House Range and one in Drum Mountains and from other localities in western Utah. Trilobites (43 species), brachiopods (eight species), mollusks (four species), and sponges (two species) are described. Three genera (Trymataspis, Utagnostus, Utaspis) and 21 species of trilobites are new. Abundant silicified specimens provide new information on morphology and ontogeny of agnostid trilobites. Evolutionary trends within Agnostidae and other families are discussed. The trilobites belong to the Bolaspidella Assemblage Zone of the standard North American Cambrian; three local assemblage subzones are named Bathyuriscus fimbriatus, Bolaspidella contracta, and Lejopyge calva.",
    openalex = "W2413383410"
}

@incollection{bisseru1967arthropods,
    author = "BISSERU, B.",
    title = "ARTHROPODS",
    year = "1967",
    booktitle = "Diseases of Man Acquired from his Pets",
    url = "https://doi.org/10.1016/b978-1-4832-0051-4.50014-x",
    doi = "10.1016/b978-1-4832-0051-4.50014-x",
    pages = "416-422"
}

@article{openalexw54684243,
    author = "Robison, Richard A.",
    title = "Annelids from the Middle Cambrian Spence Shale of Utah",
    year = "1969",
    journal = "Journal of Paleontology",
    openalex = "W54684243"
}

@misc{simonetta1970studies17,
    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.}"
}

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{doi104095103458,
    author = "Whittington, H. B.",
    title = "Yohoia Walcott and Plenocaris N. Gen., arthropods from the Burgess Shale, Middle Cambrian, British Columbia",
    year = "1974",
    url = "https://doi.org/10.4095/103458",
    doi = "10.4095/103458",
    openalex = "W2910690502"
}

@techreport{whittington1974yohoia21,
    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"
}

@techreport{briggs1976the1,
    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.}"
}

@incollection{crossref1976arthropods,
    title = "Arthropods",
    year = "1976",
    booktitle = "Animal Biochromes and Structural Colours",
    url = "https://doi.org/10.1525/9780520339422-019",
    doi = "10.1525/9780520339422-019",
    pages = "117-138"
}

A study of new specimens of the bivalved arthropod Protocaris preriosa Resser, 1929 from the Burgess Shale has added much information to the original description, and the species is removed to a new genus Bra11c/1iocaris. Prorocaris marshi Walcott, 1884 and Dioxycaris arge11ra (Walcott, 1886) are also redescribed to facilitate comparison. The cephalic region of Bra11chiocaris preriosa bore a paired antenna anterior to a pair of stout appendages which may have been chelate. Suboval valves, the dorsal margin terminating anteriorly and posteriorly in a small pointed process, covered the anterior of the body. The trunk included about 46 divisions followed by a telson bearing a pair of short pointed processes. The lamellate trunk appendages may have been biramous, with a short, segmented proximal element. The animal probably swam near the seabed by metachronal movements of the lamellate appendages, which may also have functioned in respiration. B. pretiosa shows closest affinities to the branchiopod Crustacea among extant arthropods but is considered unlikely to represent a direct evolutionary predecessor of this group. The trunk of Protocaris marshi included about 65 divisions; the tel son processes were elongate and curved. The appendages are unknown. The carapace of Dioxycaris arge11ta is similar in outline and size to that of Branchiocaris preliosa but the only known specimen is poorly preserved and lacks evidence of the soft-part morphology.

@misc{doi104095103962,
    author = "Briggs, Derek E. G.",
    title = "The Arthropod Branchiocaris N. Gen., Middle Cambrian, Burgess Shale, British Columbia",
    year = "1976",
    abstract = "A study of new specimens of the bivalved arthropod Protocaris preriosa Resser, 1929 from the Burgess Shale has added much information to the original description, and the species is removed to a new genus Bra11c/1iocaris. Prorocaris marshi Walcott, 1884 and Dioxycaris arge11ra (Walcott, 1886) are also redescribed to facilitate comparison. The cephalic region of Bra11chiocaris preriosa bore a paired antenna anterior to a pair of stout appendages which may have been chelate. Suboval valves, the dorsal margin terminating anteriorly and posteriorly in a small pointed process, covered the anterior of the body. The trunk included about 46 divisions followed by a telson bearing a pair of short pointed processes. The lamellate trunk appendages may have been biramous, with a short, segmented proximal element. The animal probably swam near the seabed by metachronal movements of the lamellate appendages, which may also have functioned in respiration. B. pretiosa shows closest affinities to the branchiopod Crustacea among extant arthropods but is considered unlikely to represent a direct evolutionary predecessor of this group. The trunk of Protocaris marshi included about 65 divisions; the tel son processes were elongate and curved. The appendages are unknown. The carapace of Dioxycaris arge11ta is similar in outline and size to that of Branchiocaris preliosa but the only known specimen is poorly preserved and lacks evidence of the soft-part morphology.",
    url = "https://doi.org/10.4095/103962",
    doi = "10.4095/103962",
    openalex = "W2910873715"
}

@misc{stmer1976the19,
    author = "Stmer, W. and Bergstrm, J",
    title = "The arthropods Mimetaster and Vachonisia from the Devonian Hunsrck Shale",
    year = "1976",
    howpublished = "Palontologische Zeitschrift, v. 50, p. 78-111",
    note = "talkorigins\_source = {true}; raw\_reference = {Stmer, W., and Bergstrm, J., 1976, The arthropods Mimetaster and Vachonisia from the Devonian Hunsrck Shale: Palontologische Zeitschrift, v. 50, p. 78-111.}"
}

@misc{briggs1977bivalved2,
    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.}"
}

Abstract The type species of the genus, N.compacta, is described from new preparations and measurements of over 100 specimens from C. D. Walcott’s original collection, and 5 from the recent re-investigation. Photographs and explanatory drawings provide the basis for considerations of mode of preservation, and lead to a new reconstruction. The dorsal exoskeleton was divided by a single articulation into two shields, each moderately convex with a raised axial region, the subcircular anterior shield overlapping for a short distance the longer posterior shield; narrow reflexed doublure on both shields. Dorsal surfaces of shields smooth, without transverse furrows, eyes absent. Axial region of anterior shield widest posteriorly, extending forward to threequarters length of shield, labrum may have been present under anterior portion. Axial region of posterior shield tapered back, reaching close to posterior margin of shield. Alimentary canal may be preserved filled with sediment, and was probably U-shaped anteriorly, broadest beneath anterior portion of axial region, tapering back to tip of posterior shield. Two types of alimentary diverticula preserved as reflective bands on anterior shield; single trunk of lateral diverticula ran transversely at mid-length and ramified beneath lateral region of shield; three pairs of axial diverticula, one per segment, originated behind main trunk of lateral diverticula and ramified in posterior part of axial region. Axial diverticula, one per segment and not ramifying, appear to have been present beneath the axial region of the posterior shield. Paired areas of muscle attachment, preserved as reflective or pyritous areas, are segmentally arranged along the axial region, one pair close together at the anterior extremity. One pair of long, uniramous, multi-jointed antennae was attached beside anterior extremity of axial region, followed by a maximum of 19 pairs of similar biramous appendages, three pairs on the posterior part of the anterior shield, remainder beneath posterior shield. Large triangular coxa strongly spinose on adaxial margin; inner, leg branch of five podomeres and terminal, thorn-like spine; large, spinose endite on proximal podomere. Outer branch arose from abaxial, dorsal margin of coxa, and consisted of slim, tapering shaft with terminal lobe, dorsal margin of shaft bore many long, thin, upward and backwardly directed lamellae. Specimens range in length from 9 to 40 mm, some 40 % of the sample being cast dorsal exoskeletons, the remainder whole animals. About one-fifth of the sample bore a posterolateral spine on the anterior shield, rather than having a rounded angle. This difference was recently used to erect two new species, Naraoia halia and N. pammon; here it is taken as the sole evidence of dimorphism in the single species N. compacta. A second species, N. spinfer, is recognized from two poorly-preserved specimens, characterized by seven pairs of lateral spines and a median posterior spine on the margins of the posterior shield; the axial region is poorly defined and appendages virtually unknown. N. compacta is considered to have been a benthonic predator and scavenger, walking, digging and raking in search of food much as did the trilobite Olenoides serratus, and to have had poor swimming powers. The lamellate outer branch of the appendage is regarded as a gill branch, aerated by currents produced when walking and swimming or drifting. There is no evidence of an abdomen or telson, so that N. compacta is a trilobite-like animal lacking the articulated thorax; it is regarded as representing a separate order of class Trilobita.

@article{doi101098rstb19770117,
    author = "Whittington, H. B.",
    title = "The Middle Cambrian trilobite Naraoia, Burgess Shale, British Columbia",
    year = "1977",
    journal = "Philosophical transactions of the Royal Society of London. Series B, Biological sciences",
    abstract = "Abstract The type species of the genus, N.compacta, is described from new preparations and measurements of over 100 specimens from C. D. Walcott’s original collection, and 5 from the recent re-investigation. Photographs and explanatory drawings provide the basis for considerations of mode of preservation, and lead to a new reconstruction. The dorsal exoskeleton was divided by a single articulation into two shields, each moderately convex with a raised axial region, the subcircular anterior shield overlapping for a short distance the longer posterior shield; narrow reflexed doublure on both shields. Dorsal surfaces of shields smooth, without transverse furrows, eyes absent. Axial region of anterior shield widest posteriorly, extending forward to threequarters length of shield, labrum may have been present under anterior portion. Axial region of posterior shield tapered back, reaching close to posterior margin of shield. Alimentary canal may be preserved filled with sediment, and was probably U-shaped anteriorly, broadest beneath anterior portion of axial region, tapering back to tip of posterior shield. Two types of alimentary diverticula preserved as reflective bands on anterior shield; single trunk of lateral diverticula ran transversely at mid-length and ramified beneath lateral region of shield; three pairs of axial diverticula, one per segment, originated behind main trunk of lateral diverticula and ramified in posterior part of axial region. Axial diverticula, one per segment and not ramifying, appear to have been present beneath the axial region of the posterior shield. Paired areas of muscle attachment, preserved as reflective or pyritous areas, are segmentally arranged along the axial region, one pair close together at the anterior extremity. One pair of long, uniramous, multi-jointed antennae was attached beside anterior extremity of axial region, followed by a maximum of 19 pairs of similar biramous appendages, three pairs on the posterior part of the anterior shield, remainder beneath posterior shield. Large triangular coxa strongly spinose on adaxial margin; inner, leg branch of five podomeres and terminal, thorn-like spine; large, spinose endite on proximal podomere. Outer branch arose from abaxial, dorsal margin of coxa, and consisted of slim, tapering shaft with terminal lobe, dorsal margin of shaft bore many long, thin, upward and backwardly directed lamellae. Specimens range in length from 9 to 40 mm, some 40 \% of the sample being cast dorsal exoskeletons, the remainder whole animals. About one-fifth of the sample bore a posterolateral spine on the anterior shield, rather than having a rounded angle. This difference was recently used to erect two new species, Naraoia halia and N. pammon; here it is taken as the sole evidence of dimorphism in the single species N. compacta. A second species, N. spinfer, is recognized from two poorly-preserved specimens, characterized by seven pairs of lateral spines and a median posterior spine on the margins of the posterior shield; the axial region is poorly defined and appendages virtually unknown. N. compacta is considered to have been a benthonic predator and scavenger, walking, digging and raking in search of food much as did the trilobite Olenoides serratus, and to have had poor swimming powers. The lamellate outer branch of the appendage is regarded as a gill branch, aerated by currents produced when walking and swimming or drifting. There is no evidence of an abdomen or telson, so that N. compacta is a trilobite-like animal lacking the articulated thorax; it is regarded as representing a separate order of class Trilobita.",
    url = "https://doi.org/10.1098/rstb.1977.0117",
    doi = "10.1098/rstb.1977.0117",
    openalex = "W2057064158"
}

(Uploaded by Plazi from the Biodiversity Heritage Library) No abstract provided.

@article{doi105281zenodo15932730,
    author = "Briggs, Derek E. G. (Derek Ernest Gilmor)",
    title = "Bivalved arthropods from the Cambrian Burgess Shale of British Columbia",
    year = "1977",
    journal = "Biodiversity Heritage Library (Smithsonian Institution)",
    abstract = "(Uploaded by Plazi from the Biodiversity Heritage Library) No abstract provided.",
    url = "https://doi.org/10.5281/zenodo.15932730",
    doi = "10.5281/zenodo.15932730",
    openalex = "W3166214822"
}

@article{briggs1978the3,
    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.}"
}

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"
}

@misc{strmer1978the18,
    author = "Strmer, W. and Bergstrm, J",
    title = "The arthropod Cheloniellon from the Devonian Hunsrck Shale",
    year = "1978",
    howpublished = "Palontologische Zeitschrift, v. 52, p. 57-81",
    note = "talkorigins\_source = {true}; raw\_reference = {Strmer, W., and Bergstrm, J., 1978, The arthropod Cheloniellon from the Devonian Hunsrck Shale: Palontologische Zeitschrift, v. 52, p. 57-81.}"
}

@misc{briggs1979anomalocaris4,
    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.}"
}

Abstract The Burgess Shale (Middle Cambrian) polychaetes Canadia spinosa Walcott, Burgessochaeta setigera (Walcott) gen. nov. and Peronochaeta dubia (Walcott) gen. nov. are redescribed on the basis of Walcott’s type specimens and on much additional material. Two new polychaetes Insolicorypha psygma gen. et sp. nov. and Stephenoscolex argutus gen. et sp. nov. are described. A poorly preserved specimen of unknown generic affinity is described as type A. The polychaetes are preserved as thin films that adhere to both sides of the split in the rock so that part and counterpart may be available. In C. spinosa, B. setigera and I. psygma, parts of the bodies such as the fascicles of setae are separated by thin layers of sediment that apparently seeped in during turbulent transport in turbidites or mudflows. The bodies therefore lie on two or more planes of microbedding and the factors that control exposure across a specimen are discussed. Aspects of the palaeoecology of the Burgess Shale are reviewed, including the distance the biota was transported prior to burial, the reasons for the exquisite preservation, and the effects of sedimentary compaction. C. spinosa was characterized by broad notosetae that extended across the dorsum, and large fascicles of neurosetae. Lobate branchiae were situated in the inter-ramal spaces. The prostomium bore a pair of elongate tentacles and the straight gut had an eversible unarmed proboscis. Several lines of evidence suggest that C. spinosa was an active benthonic swimmer. B. setigera was peculiar in possessing identical notosetae and neurosetae along the entire body. Long anterior tentacles, possibly of peristomial origin, may have been used in feeding. Indirect evidence indicates that B. setigera inhabited a burrow which it might have excavated with its proboscis. P. dubia may also have burrowed but it had uniramous parapodia bearing simple and acicular setae. The prostomium bore a pair of short appendages. I. psygma had extended neuropodia bearing cirri and elongate setae. The notopodia were reduced and cirri appear to have been wanting. The peculiar prostomium carried a pair of appendages. I. psygma is regarded as a pelagic polychaete. S. argutus possessed uniramous parapodia with simple stout setae. The bilobed prostomium bore at least one pair, and perhaps three pairs, of short appendages. Type A was the largest of the Burgess Shale polychaetes and had prominent setae on at least the anterior section of the body. Type A was a sediment eater but the feeding habits of the other polychaetes are uncertain. Particular attention is given to the influence of decay on the Burgess Shale polychaetes. To place the Burgess Shale polychaetes in some geological perspective other Cambrian worms, including a polychaete from the Spence Shale of Utah, are briefly redescribed and the late Precambrian (Ediacarian) worms Dickinsonia, Spriggina and Marywadea are assessed. Contrary to the findings of other workers, no convincing evidence for placing these latter worms in the polychaetes is forthcoming.

@article{doi101098rstb19790006,
    author = "Morris, Simon Conway",
    title = "Middle Cambrian polychaetes from the Burgess Shale of British Columbia",
    year = "1979",
    journal = "Philosophical transactions of the Royal Society of London. Series B, Biological sciences",
    abstract = "Abstract The Burgess Shale (Middle Cambrian) polychaetes Canadia spinosa Walcott, Burgessochaeta setigera (Walcott) gen. nov. and Peronochaeta dubia (Walcott) gen. nov. are redescribed on the basis of Walcott’s type specimens and on much additional material. Two new polychaetes Insolicorypha psygma gen. et sp. nov. and Stephenoscolex argutus gen. et sp. nov. are described. A poorly preserved specimen of unknown generic affinity is described as type A. The polychaetes are preserved as thin films that adhere to both sides of the split in the rock so that part and counterpart may be available. In C. spinosa, B. setigera and I. psygma, parts of the bodies such as the fascicles of setae are separated by thin layers of sediment that apparently seeped in during turbulent transport in turbidites or mudflows. The bodies therefore lie on two or more planes of microbedding and the factors that control exposure across a specimen are discussed. Aspects of the palaeoecology of the Burgess Shale are reviewed, including the distance the biota was transported prior to burial, the reasons for the exquisite preservation, and the effects of sedimentary compaction. C. spinosa was characterized by broad notosetae that extended across the dorsum, and large fascicles of neurosetae. Lobate branchiae were situated in the inter-ramal spaces. The prostomium bore a pair of elongate tentacles and the straight gut had an eversible unarmed proboscis. Several lines of evidence suggest that C. spinosa was an active benthonic swimmer. B. setigera was peculiar in possessing identical notosetae and neurosetae along the entire body. Long anterior tentacles, possibly of peristomial origin, may have been used in feeding. Indirect evidence indicates that B. setigera inhabited a burrow which it might have excavated with its proboscis. P. dubia may also have burrowed but it had uniramous parapodia bearing simple and acicular setae. The prostomium bore a pair of short appendages. I. psygma had extended neuropodia bearing cirri and elongate setae. The notopodia were reduced and cirri appear to have been wanting. The peculiar prostomium carried a pair of appendages. I. psygma is regarded as a pelagic polychaete. S. argutus possessed uniramous parapodia with simple stout setae. The bilobed prostomium bore at least one pair, and perhaps three pairs, of short appendages. Type A was the largest of the Burgess Shale polychaetes and had prominent setae on at least the anterior section of the body. Type A was a sediment eater but the feeding habits of the other polychaetes are uncertain. Particular attention is given to the influence of decay on the Burgess Shale polychaetes. To place the Burgess Shale polychaetes in some geological perspective other Cambrian worms, including a polychaete from the Spence Shale of Utah, are briefly redescribed and the late Precambrian (Ediacarian) worms Dickinsonia, Spriggina and Marywadea are assessed. Contrary to the findings of other workers, no convincing evidence for placing these latter worms in the polychaetes is forthcoming.",
    url = "https://doi.org/10.1098/rstb.1979.0006",
    doi = "10.1098/rstb.1979.0006",
    openalex = "W2172047926",
    references = "cloud1976beginnings, doi101111j146979981962tb01837x, doi1023071483846, doi1023072412725, doi105281zenodo16238847, doi105962bhlpart13989, doi105962bhltitle8596, openalexw1575297980, openalexw2604340081, openalexw589153876"
}

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{briggs1981relationships6,
    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{briggs1981the5,
    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{bruton1981the11,
    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 Six species of arthropods from the Walcott Collection, U.S. National Museum, are described. Molaria spinifera Walcott is known from over 100 specimens, a sample that reveals the morphology fairly fully. Between one and 12 specimens of the other species are known, and yield limited information. M. spinifera had a smooth, convex exoskeleton, not trilobed, the cephalic shield being a quarter-sphere in shape, eight trunk tergites diminishing in size posteriorly and the cylindrical telson having a short ventral spine and a long, jointed posterior spine. The cephalon bore a pair of short, slim antennae and three pairs of biramous appendages. There were eight pairs of similar biramous appendages on the trunk. The biramous appendage had a large basal podomere, a segmented inner walking branch, and a lobate outer branch arising from the basal podomere and bearing marginal lamellae. The sagittal length of cephalon, trunk and telson ranged from 8 to 26 mm, the posterior spine slightly exceeding this length; the smallest specimens are similar to the largest. The animal lacked eyes, and was probably benthic and may have been a scavenger and deposit feeder. Habelia optata Walcott was superficially similar to M. spinfera, the trunk being of 12 tergites; there was no cylindrical telson, but a ridged and barbed spine inserted into the 12th tergite, the spine having a joint at about two-thirds its length. The external surface of the exoskeleton was tuberculate; the pleurae of the tergites curved back increasingly strongly posteriorly, the tips being spinose. The cephalon appears to have borne a slim, short pair of antennae and two pairs of biramous appendages; the proximal portions of the jointed inner branches may have been adapted for grinding food. The first six trunk somites bore biramous limbs, the inner branch being a relatively long walking leg, the outer a lobe having marginal lamellae; on the posterior trunk somites there is no trace of the inner branch, but the outer was present. H. optata lacked eyes and was probably a benthic animal. Only the smooth exoskeleton of a possible second species, H? brevicauda Simonetta, is known, of which the posterior spine is short and bluntly rounded. The new genus and species Sarotrocercus oblita is erected for a few specimens, in which the body is about 1 cm in length, and behind which is a slim spine having a group of spines at the tip. From beneath the anterolateral margin of the cephalic shield a large eye projected, and the cephalon bore also one pair of large, jointed appendages. Behind these were pairs of lobed appendages bearing marginal lamellae, one on the cephalon and one on each of the nine trunk somites. This small species may have drifted and swum in the higher water layers, the occasional carcass lying on the sea bottom having been preserved. The single specimen of Actaeus armatus Simonetta is over 6 cm in length. The exoskeleton of this specimen is divided into cephalic shield with marginal eye lobe, 11 trunk tergites and a triangular terminal plate. The anterior cephalic appendage was Leanchoil-like, the stout proximal portion being curved and ending in a group of claws, the next two podomeres bearing long, slim extensions. The head shield also bore three pairs of biramous appendages, consisting of a small jointed inner branch and a large lobed outer branch with marginal lamellae; appendages like these outer branches are preserved beneath the trunk tergites. Only two specimens are identified as Alalcomenaeus cambricus Simonetta (length 3-4 cm). The exoskeleton is divisible into cephalic shield, trunk of probably 12 tergites, and an ovate terminal plate which has lateral bands. The cephalon has a marginal eye lobe and an anterior appendage which is broad proximally, the long distal portion being slim. The holotype shows a series of lobed appendages, the first three cephalic. Between them project the curved, pointed terminations of inner branches. The second specimen suggests that these lobed appendages bore marginal filaments, and reveals the inner branches as blade-shaped, and spinose on the inward-facing margin. These biramous appendages were present on all the trunk somites, being largest anteriorly. These remarkable appendages suggest a benthic scavenger, able to hold on to, and tear up, a carcass. ‘ Leanchoilia protogonia ’ Simonetta is most probably a composite, a poorly preserved Leanchoilia superlata lying on an unidentified, branching organism. The five species showing appendages extend greatly the known range of variation in morphology of the Burgess Shale arthropods. Affinities are discussed, but familial and higher classification is postponed, pending completion of work on all the arthropods from the shale.

@article{doi101098rstb19810033,
    author = "Whittington, H. B.",
    title = "Rare arthropods from the Burgess Shale, Middle Cambrian, British Columbia",
    year = "1981",
    journal = "Philosophical transactions of the Royal Society of London. Series B, Biological sciences",
    abstract = "Abstract Six species of arthropods from the Walcott Collection, U.S. National Museum, are described. Molaria spinifera Walcott is known from over 100 specimens, a sample that reveals the morphology fairly fully. Between one and 12 specimens of the other species are known, and yield limited information. M. spinifera had a smooth, convex exoskeleton, not trilobed, the cephalic shield being a quarter-sphere in shape, eight trunk tergites diminishing in size posteriorly and the cylindrical telson having a short ventral spine and a long, jointed posterior spine. The cephalon bore a pair of short, slim antennae and three pairs of biramous appendages. There were eight pairs of similar biramous appendages on the trunk. The biramous appendage had a large basal podomere, a segmented inner walking branch, and a lobate outer branch arising from the basal podomere and bearing marginal lamellae. The sagittal length of cephalon, trunk and telson ranged from 8 to 26 mm, the posterior spine slightly exceeding this length; the smallest specimens are similar to the largest. The animal lacked eyes, and was probably benthic and may have been a scavenger and deposit feeder. Habelia optata Walcott was superficially similar to M. spinfera, the trunk being of 12 tergites; there was no cylindrical telson, but a ridged and barbed spine inserted into the 12th tergite, the spine having a joint at about two-thirds its length. The external surface of the exoskeleton was tuberculate; the pleurae of the tergites curved back increasingly strongly posteriorly, the tips being spinose. The cephalon appears to have borne a slim, short pair of antennae and two pairs of biramous appendages; the proximal portions of the jointed inner branches may have been adapted for grinding food. The first six trunk somites bore biramous limbs, the inner branch being a relatively long walking leg, the outer a lobe having marginal lamellae; on the posterior trunk somites there is no trace of the inner branch, but the outer was present. H. optata lacked eyes and was probably a benthic animal. Only the smooth exoskeleton of a possible second species, H? brevicauda Simonetta, is known, of which the posterior spine is short and bluntly rounded. The new genus and species Sarotrocercus oblita is erected for a few specimens, in which the body is about 1 cm in length, and behind which is a slim spine having a group of spines at the tip. From beneath the anterolateral margin of the cephalic shield a large eye projected, and the cephalon bore also one pair of large, jointed appendages. Behind these were pairs of lobed appendages bearing marginal lamellae, one on the cephalon and one on each of the nine trunk somites. This small species may have drifted and swum in the higher water layers, the occasional carcass lying on the sea bottom having been preserved. The single specimen of Actaeus armatus Simonetta is over 6 cm in length. The exoskeleton of this specimen is divided into cephalic shield with marginal eye lobe, 11 trunk tergites and a triangular terminal plate. The anterior cephalic appendage was Leanchoil-like, the stout proximal portion being curved and ending in a group of claws, the next two podomeres bearing long, slim extensions. The head shield also bore three pairs of biramous appendages, consisting of a small jointed inner branch and a large lobed outer branch with marginal lamellae; appendages like these outer branches are preserved beneath the trunk tergites. Only two specimens are identified as Alalcomenaeus cambricus Simonetta (length 3-4 cm). The exoskeleton is divisible into cephalic shield, trunk of probably 12 tergites, and an ovate terminal plate which has lateral bands. The cephalon has a marginal eye lobe and an anterior appendage which is broad proximally, the long distal portion being slim. The holotype shows a series of lobed appendages, the first three cephalic. Between them project the curved, pointed terminations of inner branches. The second specimen suggests that these lobed appendages bore marginal filaments, and reveals the inner branches as blade-shaped, and spinose on the inward-facing margin. These biramous appendages were present on all the trunk somites, being largest anteriorly. These remarkable appendages suggest a benthic scavenger, able to hold on to, and tear up, a carcass. ‘ Leanchoilia protogonia ’ Simonetta is most probably a composite, a poorly preserved Leanchoilia superlata lying on an unidentified, branching organism. The five species showing appendages extend greatly the known range of variation in morphology of the Burgess Shale arthropods. Affinities are discussed, but familial and higher classification is postponed, pending completion of work on all the arthropods from the shale.",
    url = "https://doi.org/10.1098/rstb.1981.0033",
    doi = "10.1098/rstb.1981.0033",
    openalex = "W2167988079",
    references = "doi101016s003130251638922x, doi101038scientificamerican0779122, doi101098rstb19780005, doi101146annureves10110179001551, doi1023071483846, doi1023072412988, doi104095103962, doi105281zenodo16273729, doi105281zenodo16490103, openalexw2601410785"
}

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"
}

@incollection{weisbroth1982arthropods,
    author = "Weisbroth, Steven H.",
    title = "Arthropods",
    year = "1982",
    booktitle = "Diseases",
    url = "https://doi.org/10.1016/b978-0-12-262502-2.50028-6",
    doi = "10.1016/b978-0-12-262502-2.50028-6",
    pages = "385-402"
}

@misc{briggs1983affinities7,
    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.}"
}

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"
}

@book{briggs1984exceptionally9,
    author = "Briggs, D. E. G. and Robinson, R. A",
    title = "Exceptionally preserved nontrilobite arthropods and Anomalocaris from the Middle Cambrian of Utah",
    year = "1984",
    publisher = "University of Kansas Paleontological Contributions; Paper 111",
    note = "talkorigins\_source = {true}; raw\_reference = {Briggs, D. E. G., and Robinson, R. A., 1984, Exceptionally preserved nontrilobite arthropods and Anomalocaris from the Middle Cambrian of Utah: University of Kansas Paleontological Contributions; Paper 111.}"
}

@misc{briggs1985les8,
    author = "Briggs, D. E. G",
    title = "Les premiers arthopodes",
    year = "1985",
    howpublished = "La Recherche, v. 16, p. 340-349",
    note = "talkorigins\_source = {true}; raw\_reference = {Briggs, D. E. G., 1985, Les premiers arthopodes: La Recherche, v. 16, p. 340-349.}"
}

@article{briggs1985modes10,
    author = "Briggs, D. E. G. and Whittington, H. B",
    title = "Modes of life of arthropods from the Burgess Shale, British Columbia",
    year = "1985",
    journal = "Transactions of the Royal Society of Edinburgh, v. 76, p. 149-160",
    note = "talkorigins\_source = {true}; raw\_reference = {Briggs, D. E. G., and Whittington, H. B., 1985, Modes of life of arthropods from the Burgess Shale, British Columbia: Transactions of the Royal Society of Edinburgh, v. 76, p. 149-160.}"
}

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 Isolated specimens of the appendage Anomalocaris canadensis have long been known; a single incomplete specimen of an animal having a pair of these appendages attached anteriorly is described. Seven dorsoventrally compressed, partly complete individuals of a similar animal that had a different pair of appendages (‘F’ of Briggs 1979) attached anteriorly are described, together with two obliquely compressed individuals that are thought to be conspecific. Surrounding the mouth of this latter species is a circlet of plates identical with the supposed medusoid coelenterate Peytoia nathorsti; this species is referred to Anomalocaris; Laggania is a junior synonym. As now understood, Anomalocaris was an animal that reached a length of 0.5 m, the elongate body having a head region bearing one pair of large, lateral eye lobes, each borne on a short stalk, the single pair of appendages attached at the ventral, anterior margin. The 13 segments of the appendage in A. canadensis bore paired spines on the inner side, short spines on the outer side, and there was a terminal, spinose 14th segment. The appendage in A. nathorsti consisted of 11 segments, the 2nd to 10th bearing on the inner side a graduated series of spinose blades, and spines on the lateral and outer sides, the terminal 11th segment ending in a group of spines. The circlet of plates surrounding the mouth was situated ventrally on the head region immediately behind the appendages; the plates bore teeth and the circlet constituted a jaw mechanism; additional groups of spines were present in the buccal cavity. Beneath the head region, behind the mouth, were three pairs of semicircular flaps, strongly overlapping: on the tapering trunk were 11 pairs of triangular lateral lobes, widest at the mid-length of the trunk, reduced progressively in size backward. These lobes were strongly overlapping in the same sense as the flaps on the head, and attached low on the sides. The trunk termination was short and blunt, without any projecting spine or lobe. Attached to the side of the body, above each flap and lateral lobe, was a multi-lamellar structure, apparently a gill. A thin cuticle covered the head region dorsally, and ventrally around the appendages and jaw circlet, behind this becoming a lateral strip that narrowed backward. It is suggested that a thin cuticle covered the trunk region dorsally and hung down beside the gills; this covering may have been continuous, but possibly was divided into tergites. Irregular patches of apatite, and some matrix, occur in the trace of the alimentary canal, which extended to the tip of the trunk. Mineralized patches occur in association with the gills, and as transverse strips, presumed traces of some internal organ or structure. The cuticle of the appendages and jaw circlet was presumably stout, hence these parts of the body were more resistant to decay and so were preserved in isolation. The thin cuticle of the lateral lobes shows rays which were presumably thicker and strengthening in function. We suggest that this animal, the largest known from Cambrian rocks, swam by using the series of closely spaced lateral lobes essentially as a lateral fin along which waves of motion were propagated. If the waves were moved in either the same, or opposite, sense on each side, considerable manoeuvrability would have resulted. The anterior pair of appendages, and jaw mechanism, would have made Anomalocaris a formidable predator, particularly on soft-bodied benthos including the abundant arthropods without a mineralized exoskeleton. No fragments of hard parts have been observed in the gut, but there is evidence that it may have inflicted wounds on trilobites. Anomalocaris was a metameric animal, and had one pair of jointed appendages and a unique circlet of jaw plates. We do not consider it an arthropod, but the representative of a hitherto unknown phylum. It is best known from A. nathorsti, the single specimen of A. canadensis having a different appendage but the rest of the body similar, probably including the jaw circlet. The evidence is insufficient to reach any conclusion on whether or not these two 'species' may be sexual dimorphs of a single species. The single specimen of Amiella ornata is redescribed. It shows what may be lateral lobes like those of Anomalcris, but other features unlike it. We conclude that this specimen is not an example of Sidneyia inexpectans, and is too incomplete for its relationship to be determined.

@article{doi101098rstb19850096,
    author = "Whittington, H. B. and Briggs, Derek E. G.",
    title = "The largest Cambrian animal, Anomalocaris, Burgess Shale, British-Columbia",
    year = "1985",
    journal = "Philosophical transactions of the Royal Society of London. Series B, Biological sciences",
    abstract = "Abstract Isolated specimens of the appendage Anomalocaris canadensis have long been known; a single incomplete specimen of an animal having a pair of these appendages attached anteriorly is described. Seven dorsoventrally compressed, partly complete individuals of a similar animal that had a different pair of appendages (‘F’ of Briggs 1979) attached anteriorly are described, together with two obliquely compressed individuals that are thought to be conspecific. Surrounding the mouth of this latter species is a circlet of plates identical with the supposed medusoid coelenterate Peytoia nathorsti; this species is referred to Anomalocaris; Laggania is a junior synonym. As now understood, Anomalocaris was an animal that reached a length of 0.5 m, the elongate body having a head region bearing one pair of large, lateral eye lobes, each borne on a short stalk, the single pair of appendages attached at the ventral, anterior margin. The 13 segments of the appendage in A. canadensis bore paired spines on the inner side, short spines on the outer side, and there was a terminal, spinose 14th segment. The appendage in A. nathorsti consisted of 11 segments, the 2nd to 10th bearing on the inner side a graduated series of spinose blades, and spines on the lateral and outer sides, the terminal 11th segment ending in a group of spines. The circlet of plates surrounding the mouth was situated ventrally on the head region immediately behind the appendages; the plates bore teeth and the circlet constituted a jaw mechanism; additional groups of spines were present in the buccal cavity. Beneath the head region, behind the mouth, were three pairs of semicircular flaps, strongly overlapping: on the tapering trunk were 11 pairs of triangular lateral lobes, widest at the mid-length of the trunk, reduced progressively in size backward. These lobes were strongly overlapping in the same sense as the flaps on the head, and attached low on the sides. The trunk termination was short and blunt, without any projecting spine or lobe. Attached to the side of the body, above each flap and lateral lobe, was a multi-lamellar structure, apparently a gill. A thin cuticle covered the head region dorsally, and ventrally around the appendages and jaw circlet, behind this becoming a lateral strip that narrowed backward. It is suggested that a thin cuticle covered the trunk region dorsally and hung down beside the gills; this covering may have been continuous, but possibly was divided into tergites. Irregular patches of apatite, and some matrix, occur in the trace of the alimentary canal, which extended to the tip of the trunk. Mineralized patches occur in association with the gills, and as transverse strips, presumed traces of some internal organ or structure. The cuticle of the appendages and jaw circlet was presumably stout, hence these parts of the body were more resistant to decay and so were preserved in isolation. The thin cuticle of the lateral lobes shows rays which were presumably thicker and strengthening in function. We suggest that this animal, the largest known from Cambrian rocks, swam by using the series of closely spaced lateral lobes essentially as a lateral fin along which waves of motion were propagated. If the waves were moved in either the same, or opposite, sense on each side, considerable manoeuvrability would have resulted. The anterior pair of appendages, and jaw mechanism, would have made Anomalocaris a formidable predator, particularly on soft-bodied benthos including the abundant arthropods without a mineralized exoskeleton. No fragments of hard parts have been observed in the gut, but there is evidence that it may have inflicted wounds on trilobites. Anomalocaris was a metameric animal, and had one pair of jointed appendages and a unique circlet of jaw plates. We do not consider it an arthropod, but the representative of a hitherto unknown phylum. It is best known from A. nathorsti, the single specimen of A. canadensis having a different appendage but the rest of the body similar, probably including the jaw circlet. The evidence is insufficient to reach any conclusion on whether or not these two 'species' may be sexual dimorphs of a single species. The single specimen of Amiella ornata is redescribed. It shows what may be lateral lobes like those of Anomalcris, but other features unlike it. We conclude that this specimen is not an example of Sidneyia inexpectans, and is too incomplete for its relationship to be determined.",
    url = "https://doi.org/10.1098/rstb.1985.0096",
    doi = "10.1098/rstb.1985.0096",
    openalex = "W2026507180",
    references = "doi1010079789401160094, doi101098rstb19750033, doi101098rstb19810007, doi101098rstb19810164, doi101126science2224620163, doi101127njgpa1491975286, doi101146annureves10110179001551, doi1023071483846, doi1023072412988, doi105281zenodo16490103, openalexw1549935978, openalexw2601410785"
}

@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"
}

@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{xianguang1987early15,
    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{xianguang1987three14,
    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{xianguang1987two13,
    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{dzik1988the12,
    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.}"
}

@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"
}

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"
}

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"
}

Three major arguments have been raised against the crucial claim, documented by Whittington and colleagues for the Burgess Shale fauna, and so contrary to traditional views, that disparity of anatomical design reached an early maximum in the history of multicellular life: (1) the presence of many early taxa with low membership and high rank is an artifact of naming; (2) cladistic analysis of Burgess arthropods negates the claim for greater early disparity; and (3) Whittington's argument is a retrospective fallacy based on assigning high rank to differentia only by virtue of their later capacity to define major branches. I show that all these arguments are either false or illogical, and that the claim for increased early disparity is justified: (1) Taxonomic rank is an artifact, but no one has ever based a claim for greater disparity on this false criterion. (2) Cladistics can only deal with branching order, whereas disparity is a phenetic issue. These two legitimate aspects of evolutionary “relationship” are logically distinct. The rooting of a cladogram only illustrates monophyletic ancestry (which no one doubts, as we are not creationists), and cannot measure disparity. (3) The active stabilization of the differentia of Baupläne (for genetic and developmental reasons only dimly understood) provides a powerful rationale for weighting these characters in considerations of disparity; nothing had so stabilized in the Burgess fauna. If these differentia were steadily changing contingencies, rather than actively stabilized features with “deep” architectural status, then the retrospective argument would be justified. Although the three arguments are wrong, the claim for greater early disparity cannot be confidently established until we develop quantitative techniques for the characterization of morphospace and its differential filling through time. This is a dauntingly difficult problem, much harder than cladistic ordering, but not intractable.

@article{doi101017s0094837300010745,
    author = "Gould, Stephen Jay",
    title = "The disparity of the Burgess Shale arthropod fauna and the limits of cladistic analysis: why we must strive to quantify morphospace",
    year = "1991",
    journal = "Paleobiology",
    abstract = "Three major arguments have been raised against the crucial claim, documented by Whittington and colleagues for the Burgess Shale fauna, and so contrary to traditional views, that disparity of anatomical design reached an early maximum in the history of multicellular life: (1) the presence of many early taxa with low membership and high rank is an artifact of naming; (2) cladistic analysis of Burgess arthropods negates the claim for greater early disparity; and (3) Whittington's argument is a retrospective fallacy based on assigning high rank to differentia only by virtue of their later capacity to define major branches. I show that all these arguments are either false or illogical, and that the claim for increased early disparity is justified: (1) Taxonomic rank is an artifact, but no one has ever based a claim for greater disparity on this false criterion. (2) Cladistics can only deal with branching order, whereas disparity is a phenetic issue. These two legitimate aspects of evolutionary “relationship” are logically distinct. The rooting of a cladogram only illustrates monophyletic ancestry (which no one doubts, as we are not creationists), and cannot measure disparity. (3) The active stabilization of the differentia of Baupläne (for genetic and developmental reasons only dimly understood) provides a powerful rationale for weighting these characters in considerations of disparity; nothing had so stabilized in the Burgess fauna. If these differentia were steadily changing contingencies, rather than actively stabilized features with “deep” architectural status, then the retrospective argument would be justified. Although the three arguments are wrong, the claim for greater early disparity cannot be confidently established until we develop quantitative techniques for the characterization of morphospace and its differential filling through time. This is a dauntingly difficult problem, much harder than cladistic ordering, but not intractable.",
    url = "https://doi.org/10.1017/s0094837300010745",
    doi = "10.1017/s0094837300010745",
    openalex = "W2122888389",
    references = "doi101098rstb19810033"
}

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"
}

@incollection{wehner1992arthropods,
    author = "Wehner, Rüdiger",
    title = "Arthropods",
    year = "1992",
    booktitle = "Animal Homing",
    url = "https://doi.org/10.1007/978-94-011-1588-9\_3",
    doi = "10.1007/978-94-011-1588-9\_3",
    pages = "45-144"
}

@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"
}

Disparity is a measure of the range or significance of morphology in a given sample of organisms, as opposed to diversity, which is expressed in terms of the number (and sometimes ranking) of taxa. At present there is no agreed definition of disparity, much less any consensus on how to measure it. Two possible categories of metric are considered here, one independent of any hypothesis of relationship (phenetics), the other constrained within an evolutionary framework (cladistics). The Early Cambrian radiation was clearly a period of significant morphologic and taxonomic diversification. However, we question the interpretation of its first generation products as numerous body plans at the highest level. Four phenetic and two cladistic measures have been used to compare disparity among Cambrian arthropods with that in the living fauna. Phenetic methods assessing character-state variability and the amount of morphological attribute space occupied yield similar results for Cambrian and Recent arthropods. Assessments of disparity within a taxonomic framework rely on the identification of particular characters that delineate higher level body plans. This requires a phylogenetic interpretation, a cladistic investigation of hierarchical structure in the data. Both sets of arthropods fall within the same major clades, and within this cladistic framework the amount of character-state evolution in the two groups is comparable. None of these methods identifies markedly greater disparity among the Cambrian compared with the Recent taxa. Although measures of disparity are applied here to a consideration of the Cambrian radiation, the metrics clearly have a much wider potential for estimating macroevolutionary trends independently from existing taxonomic frameworks. Geometric morphometry is ideal for measuring morphological variety at lower taxonomic levels, but it requires the recognition of homologous landmarks in all the forms under comparison, or the identification of entire homologous structures. Conventional phenetics has much wider application as it can operate on data coded as discrete homologous character states (this facility is also a requirement of cladistics), which are a more appropriate basis for comparing disparity in markedly dissimilar forms.

@article{doi101017s009483730001263x,
    author = "Wills, Matthew A. and Briggs, Derek E. G. and Fortey, Richard A.",
    title = "Disparity as an evolutionary index: a comparison of Cambrian and Recent arthropods",
    year = "1994",
    journal = "Paleobiology",
    abstract = "Disparity is a measure of the range or significance of morphology in a given sample of organisms, as opposed to diversity, which is expressed in terms of the number (and sometimes ranking) of taxa. At present there is no agreed definition of disparity, much less any consensus on how to measure it. Two possible categories of metric are considered here, one independent of any hypothesis of relationship (phenetics), the other constrained within an evolutionary framework (cladistics). The Early Cambrian radiation was clearly a period of significant morphologic and taxonomic diversification. However, we question the interpretation of its first generation products as numerous body plans at the highest level. Four phenetic and two cladistic measures have been used to compare disparity among Cambrian arthropods with that in the living fauna. Phenetic methods assessing character-state variability and the amount of morphological attribute space occupied yield similar results for Cambrian and Recent arthropods. Assessments of disparity within a taxonomic framework rely on the identification of particular characters that delineate higher level body plans. This requires a phylogenetic interpretation, a cladistic investigation of hierarchical structure in the data. Both sets of arthropods fall within the same major clades, and within this cladistic framework the amount of character-state evolution in the two groups is comparable. None of these methods identifies markedly greater disparity among the Cambrian compared with the Recent taxa. Although measures of disparity are applied here to a consideration of the Cambrian radiation, the metrics clearly have a much wider potential for estimating macroevolutionary trends independently from existing taxonomic frameworks. Geometric morphometry is ideal for measuring morphological variety at lower taxonomic levels, but it requires the recognition of homologous landmarks in all the forms under comparison, or the identification of entire homologous structures. Conventional phenetics has much wider application as it can operate on data coded as discrete homologous character states (this facility is also a requirement of cladistics), which are a more appropriate basis for comparing disparity in markedly dissimilar forms.",
    url = "https://doi.org/10.1017/s009483730001263x",
    doi = "10.1017/s009483730001263x",
    openalex = "W2131955742",
    references = "crossref1977chapter, doi101007bf02289565, doi101007bf02289630, doi101007bf02289694, doi101017s0094837300015864, doi101093biomet5334325, doi101098rstb19810007, doi101098rstb19830020, doi101098rstb19850005, doi101111j155856461982tb05453x, doi10113719781611970319, doi101144gsjgs14940631, doi1023072288218, doi1023072346439, doi103133ofr81743, doi105281zenodo16435756, doi105860choice273873, openalexw2754161204, openalexw2944885317"
}

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 remarkable “evolution” of the reconstructions of Anomalocaris, the extraordinary predator from the 515 million year old Middle Cambrian Burgess Shale of British Columbia, reflects the dramatic changes in our interpretation of early animal life on Earth over the past 100 years. Beginning in 1892 with a claw identified as the abdomen and tail of a phyllocarid crustacean, parts of Anomalocaris have been described variously as a jellyfish, a sea-cucumber, a polychaete worm, a composite of a jellyfish and sponge, or have been attached to other arthropods as appendages. Charles D. Walcott collected complete specimens of Anomalocaris nathorsti between 1911 and 1917, and a Geological Survey of Canada party collected an almost complete specimen of Anomalocaris canadensis in 1966 or 1967, but neither species was adequately described until 1985. At that time they were interpreted by Whittington and Briggs to be representatives of “a hitherto unknown phylum.” Here, using recently collected specimens, the two species are newly reconstructed and described in the genera Anomalocaris and Laggania, and interpreted to be members of an extinct arthropod class, Dinocarida, and order Radiodonta, new to science. The long history of inaccurate reconstruction and mistaken identification of Anomalocaris and Laggania exemplifies our great difficulty in visualizing and classifying, from fossil remains, the many Cambrian animals with no apparent living descendants.

@article{doi101017s0022336000023362,
    author = "Collins, Desmond",
    title = "The “evolution” of Anomalocaris and its classification in the arthropod class Dinocarida (nov.) and order Radiodonta (nov.)",
    year = "1996",
    journal = "Journal of Paleontology",
    abstract = "The remarkable “evolution” of the reconstructions of Anomalocaris, the extraordinary predator from the 515 million year old Middle Cambrian Burgess Shale of British Columbia, reflects the dramatic changes in our interpretation of early animal life on Earth over the past 100 years. Beginning in 1892 with a claw identified as the abdomen and tail of a phyllocarid crustacean, parts of Anomalocaris have been described variously as a jellyfish, a sea-cucumber, a polychaete worm, a composite of a jellyfish and sponge, or have been attached to other arthropods as appendages. Charles D. Walcott collected complete specimens of Anomalocaris nathorsti between 1911 and 1917, and a Geological Survey of Canada party collected an almost complete specimen of Anomalocaris canadensis in 1966 or 1967, but neither species was adequately described until 1985. At that time they were interpreted by Whittington and Briggs to be representatives of “a hitherto unknown phylum.” Here, using recently collected specimens, the two species are newly reconstructed and described in the genera Anomalocaris and Laggania, and interpreted to be members of an extinct arthropod class, Dinocarida, and order Radiodonta, new to science. The long history of inaccurate reconstruction and mistaken identification of Anomalocaris and Laggania exemplifies our great difficulty in visualizing and classifying, from fossil remains, the many Cambrian animals with no apparent living descendants.",
    url = "https://doi.org/10.1017/s0022336000023362",
    doi = "10.1017/s0022336000023362",
    openalex = "W2345626479",
    references = "openalexw2601410785"
}

Diffraction gratings are reported from external surfaces of the hard, protective parts of Wiwaxia corrugata, Canadia spinosa and Marrella splendens from the Burgess Shale (Middle Cambrian (515 million years), British Columbia). As a consequence, these animals would have displayed iridescence in their natural environment: Cambrian animals have previously been accurately reconstructed in black and white only. A diversity of extant marine animals inhabiting a similar depth to the Burgess Shale fauna possess functional diffraction gratings. The Cambrian is a unique period in the history of animal life where predatory lifestyles and eyes capable of producing visual images were evolving rapidly. The discovery of colour in Cambrian animals prompts a new hypothesis on the initiation of the ‘Big Bang’ in animal evolution which occurred during the Cambrian: light was introduced into the behavioural systems of metazoan animals for the first time. This introduction, of what was to become generally the most powerful stimulus in metazoan behavioural systems, would have triggered turbulence in metazoan evolution.

@article{doi101098rspb19980385,
    author = "Parker, Andrew R.",
    title = "Colour in Burgess Shale animals and the effect of light on evolution in the Cambrian",
    year = "1998",
    journal = "Proceedings of the Royal Society B Biological Sciences",
    abstract = "Diffraction gratings are reported from external surfaces of the hard, protective parts of Wiwaxia corrugata, Canadia spinosa and Marrella splendens from the Burgess Shale (Middle Cambrian (515 million years), British Columbia). As a consequence, these animals would have displayed iridescence in their natural environment: Cambrian animals have previously been accurately reconstructed in black and white only. A diversity of extant marine animals inhabiting a similar depth to the Burgess Shale fauna possess functional diffraction gratings. The Cambrian is a unique period in the history of animal life where predatory lifestyles and eyes capable of producing visual images were evolving rapidly. The discovery of colour in Cambrian animals prompts a new hypothesis on the initiation of the ‘Big Bang’ in animal evolution which occurred during the Cambrian: light was introduced into the behavioural systems of metazoan animals for the first time. This introduction, of what was to become generally the most powerful stimulus in metazoan behavioural systems, would have triggered turbulence in metazoan evolution.",
    url = "https://doi.org/10.1098/rspb.1998.0385",
    doi = "10.1098/rspb.1998.0385",
    openalex = "W1977013458"
}

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"
}

Exceptionally preserved, non-biomineralizing fossils contribute importantly to resolving details of the Cambrian explosion, but little to its overall patterns. Six distinct "types" of exceptional preservation are identified for the terminal Proterozoic-Cambrian interval, each of which is dependent on particular taphonomic circumstances, typically restricted both in space and time. Taphonomic pathways yielding exceptional preservation were particularly variable through the Proterozoic-Cambrian transition, at least in part a consequence of contemporaneous evolutionary innovations. Combined with the reasonably continuous record of "Doushantuo-type preservation," and the fundamentally more robust records of shelly fossils, phytoplankton cysts and trace fossils, these taphonomic perturbations contribute to the documentation of major evolutionary and biogeochemical shifts through the terminal Proterozoic and early Cambrian.Appreciation of the relationship between taphonomic pathway and fossil expression serves as a useful tool for interpreting exceptionally preserved, often problematic, early Cambrian fossils. In shale facies, for example, flattened non-biomineralizing structures typically represent the remains of degradation-resistant acellular and extracellular "tissues" such as chaetae and cuticles, whereas three-dimensional preservation represents labile cellular tissues with a propensity for attracting and precipitating early diagenetic minerals. Such distinction helps to identify the acuticular integument of hyolithids, the chaetae-like nature of Wiwaxia sclerites, the chaetognath-like integument of Amiskwia, the midgut glands of various Burgess Shale arthropods, and the misidentification of deposit-feeding arthropods in the Chengjiang biota. By the same reasoning, putative lobopods in the Sirius Passet biota and putative deuterostomes in the Chengiang biota are better interpreted as arthropods.

@article{doi101093icb431166,
    author = "Butterfield, Nicholas J.",
    title = "Exceptional Fossil Preservation and the Cambrian Explosion",
    year = "2003",
    journal = "Integrative and Comparative Biology",
    abstract = {Exceptionally preserved, non-biomineralizing fossils contribute importantly to resolving details of the Cambrian explosion, but little to its overall patterns. Six distinct "types" of exceptional preservation are identified for the terminal Proterozoic-Cambrian interval, each of which is dependent on particular taphonomic circumstances, typically restricted both in space and time. Taphonomic pathways yielding exceptional preservation were particularly variable through the Proterozoic-Cambrian transition, at least in part a consequence of contemporaneous evolutionary innovations. Combined with the reasonably continuous record of "Doushantuo-type preservation," and the fundamentally more robust records of shelly fossils, phytoplankton cysts and trace fossils, these taphonomic perturbations contribute to the documentation of major evolutionary and biogeochemical shifts through the terminal Proterozoic and early Cambrian.Appreciation of the relationship between taphonomic pathway and fossil expression serves as a useful tool for interpreting exceptionally preserved, often problematic, early Cambrian fossils. In shale facies, for example, flattened non-biomineralizing structures typically represent the remains of degradation-resistant acellular and extracellular "tissues" such as chaetae and cuticles, whereas three-dimensional preservation represents labile cellular tissues with a propensity for attracting and precipitating early diagenetic minerals. Such distinction helps to identify the acuticular integument of hyolithids, the chaetae-like nature of Wiwaxia sclerites, the chaetognath-like integument of Amiskwia, the midgut glands of various Burgess Shale arthropods, and the misidentification of deposit-feeding arthropods in the Chengjiang biota. By the same reasoning, putative lobopods in the Sirius Passet biota and putative deuterostomes in the Chengiang biota are better interpreted as arthropods.},
    url = "https://doi.org/10.1093/icb/43.1.166",
    doi = "10.1093/icb/43.1.166",
    openalex = "W2181027699",
    references = "doi1010160016703789901919, doi101017s000632310000548x, doi101017s0094837300009994, doi101017s0094837300012082, doi10103834391, doi10103835318, doi101098rstb19790006, doi101098rstb19850005, doi101111j1469185x1999tb00046x, doi101111j150239311975tb01311x, doi101111j150239311994tb01558x, doi101111j150239311995tb01587x, doi101111j150239311995tb01591x, doi101126science1066611, doi101126science28153801173, doi1016660094837320000260386bpngns20co2, doi1016660094837320020280155lgatio20co2, doi1023073514743, doi1023073515360, openalexw2326083785, openalexw2754161204, openalexw3127114020, openalexw659399033"
}

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"
}

@article{doi101038nature04894,
    author = "Caron, Jean‐Bernard and Scheltema, Amélie H. and Schänder, Christoffer and Rudkin, David M.",
    title = "A soft-bodied mollusc with radula from the Middle Cambrian Burgess Shale",
    year = "2006",
    journal = "Nature",
    url = "https://doi.org/10.1038/nature04894",
    doi = "10.1038/nature04894",
    openalex = "W2001245937",
    references = "doi101017cbo9780511735769004, doi101017s000632310000548x, doi101038345802a0, doi101073pnas0401670101, doi101073pnas0403984101, doi101093oso97801985498020010001, doi101098rstb19850005, doi101146annurevearth33092203122519, doi102110palo2003p05070r, doi1023073515363, openalexw1557570128, openalexw2606050730, openalexw659399033"
}

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"
}

Abstract: Current models for the exceptional preservation of Burgess Shale fossils have focused on either the HF‐extractable carbonaceous compressions or the mineral films identified by elemental mapping. BSEM, EDX and microprobe analysis of two‐dimensionally preserved Marpolia, Wiwaxia and Burgessia identifies the presence of both carbonaceous and aluminosilicate films for most features, irrespective of original lability. In the light of the deep burial and greenschist facies metamorphism documented for the Burgess Shale, the aluminosilicate films are identified as products of late‐stage volatilization and coincident mineralization of pre‐existing compression fossils, whereas the three‐dimensionally preserved gut‐caecal system of Burgessia is interpreted as an aluminosilicate replacement of a pre‐existing carbonate phase. The case for late diagenetic emplacement of aluminosilicate minerals is supported by the extensive aluminosilicification of trilobite shell and (originally) calcareous veinlets in the Burgess Shale, as well as documentation of other secondarily aluminosilicified compression fossils. By distinguishing late diagenetic alteration from the early diagenetic processes responsible for exceptional preservation, it is possible to reconcile the range of preservational modes currently expressed in the Burgess Shale.

@article{doi101111j14754983200700656x,
    author = "Butterfield, Nicholas J. and Balthasar, Uwe and WILSON, LUCY A.",
    title = "FOSSIL DIAGENESIS IN THE BURGESS SHALE",
    year = "2007",
    journal = "Palaeontology",
    abstract = "Abstract: Current models for the exceptional preservation of Burgess Shale fossils have focused on either the HF‐extractable carbonaceous compressions or the mineral films identified by elemental mapping. BSEM, EDX and microprobe analysis of two‐dimensionally preserved Marpolia, Wiwaxia and Burgessia identifies the presence of both carbonaceous and aluminosilicate films for most features, irrespective of original lability. In the light of the deep burial and greenschist facies metamorphism documented for the Burgess Shale, the aluminosilicate films are identified as products of late‐stage volatilization and coincident mineralization of pre‐existing compression fossils, whereas the three‐dimensionally preserved gut‐caecal system of Burgessia is interpreted as an aluminosilicate replacement of a pre‐existing carbonate phase. The case for late diagenetic emplacement of aluminosilicate minerals is supported by the extensive aluminosilicification of trilobite shell and (originally) calcareous veinlets in the Burgess Shale, as well as documentation of other secondarily aluminosilicified compression fossils. By distinguishing late diagenetic alteration from the early diagenetic processes responsible for exceptional preservation, it is possible to reconcile the range of preservational modes currently expressed in the Burgess Shale.",
    url = "https://doi.org/10.1111/j.1475-4983.2007.00656.x",
    doi = "10.1111/j.1475-4983.2007.00656.x",
    openalex = "W2035625131",
    references = "briggs1994decay, doi1010079783642878138, doi101016jpalaeo200407034, doi101017s0094837300009994, doi101093icb431166, doi101111j150239311995tb01587x, doi101126science28153801173, doi101130g206401, doi1016660094837320020280155lgatio20co2, doi105281zenodo15992748, doi105860choice284524, openalexw3127114020"
}

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"
}

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"
}

The Middle Cambrian Spence Shale Member (Langston Formation) and Wheeler and Marjum Formations of Utah are known to contain a diverse soft-bodied fauna, but important new paleontological material continues to be uncovered from these strata. New specimens of anomalocaridids include the largest and smallest near complete examples yet reported from Utah. New material of stem group arthropods includes two new genera and species of arachnomorphs: Nettapezoura basilika and Dicranocaris guntherorum. Other new arachnomorph material includes a new species of Leanchoilia comparable to L. protogonia Simonetta, 1970; Leanchoilia superlata? Walcott, 1912; Sidneyia Walcott, 1911a; and Mollisonia symmetrica Walcott, 1912. L. protogonia from the Burgess Shale is confirmed as a separate species and is not a composite fossil. The first example of the trilobite Elrathia kingii preserving traces of the appendages is described. In addition, new material of the bivalved arthropods Canadaspis Novozhilov in Orlov, 1960; Branchiocaris Briggs, 1976; Waptia Walcott, 1912; and Isoxys Walcott, 1890 is described.

@article{doi101666060861,
    author = "Briggs, Derek E. G. and Lieberman, Bruce S. and Hendricks, Jonathan R. and Halgedahl, Susan L. and Jarrard, Richard D.",
    title = "Middle Cambrian arthropods from Utah",
    year = "2008",
    journal = "Journal of Paleontology",
    abstract = "The Middle Cambrian Spence Shale Member (Langston Formation) and Wheeler and Marjum Formations of Utah are known to contain a diverse soft-bodied fauna, but important new paleontological material continues to be uncovered from these strata. New specimens of anomalocaridids include the largest and smallest near complete examples yet reported from Utah. New material of stem group arthropods includes two new genera and species of arachnomorphs: Nettapezoura basilika and Dicranocaris guntherorum. Other new arachnomorph material includes a new species of Leanchoilia comparable to L. protogonia Simonetta, 1970; Leanchoilia superlata? Walcott, 1912; Sidneyia Walcott, 1911a; and Mollisonia symmetrica Walcott, 1912. L. protogonia from the Burgess Shale is confirmed as a separate species and is not a composite fossil. The first example of the trilobite Elrathia kingii preserving traces of the appendages is described. In addition, new material of the bivalved arthropods Canadaspis Novozhilov in Orlov, 1960; Branchiocaris Briggs, 1976; Waptia Walcott, 1912; and Isoxys Walcott, 1890 is described.",
    url = "https://doi.org/10.1666/06-086.1",
    doi = "10.1666/06-086.1",
    openalex = "W2129198432",
    references = "doi101098rstb19810033"
}

@incollection{hangay2008arthropods,
    author = "Hangay, George and Gayubo, Severiano F. and Hoy, Marjorie A. and Goula, Marta and Sanborn, Allen and Morrill, Wendell. L. and GÄde, Gerd and Marco, Heather G. and Kabissa, Joe C. B. and Ellis, Jamie and Ellis, Amanda and Lord, Cynthia C. and Schabel, Hans G. and Heppner, John B. and Schabel, Hans G. and Heppner, John B. and Heppner, John B. and Heppner, John B. and Nadel, Hannah and Easton, Emmett R. and Mcsorley, Robert and Napper, Emma and Pickett, John A. and Nation, James L. and Stange, Lionel and Goettel, Mark S. and Capinera, John L. and Nation, James L. and Paulson, Gregory S. and Blum, Murray S. and Kouloussis, Nikos A. and Heppner, John B. and Hoy, Marjorie A. and Heppner, John B. and Heppner, John B. and Capinera, John L. and Heppner, John B and Heppner, John B. and Heppner, John B. and Chiappini, Elisabetta and Heppner, John B. and Gayubo, Severiano F. and Davidson, Diane W. and Oi, David H. and Sullivan, Daniel J. and Sanford, Malcolm T. and Tew, James E. and O'neill, Kevin M. and Mcauslane, Heather J. and Agnello, Arthur M. and Wallace, John R. and Rinkevich, Frank D. L. and Heppner, John B. and Heppner, John B. and Klassen, Waldemar and Uspensky, Igor and Wild, Alex and Capinera, John L. and Alborn, Hans T. and Schmelz, Eric A. and Tsai, James H. and Capinera, John L. and Ribes, Eva and Goula, Marta and JeremÍas, Xavier and Capinera, John L. and Matsumoto, Yoshiharu and Hoy, Marjorie A. and Heppner, John B. and Heppner, John B. and Heppner, John B. and Capinera, John L. and Heppner, John B. and Heppner, John B. and Nayar, Jai K.",
    title = "Arthropods",
    year = "2008",
    booktitle = "Encyclopedia of Entomology",
    url = "https://doi.org/10.1007/978-1-4020-6359-6\_357",
    doi = "10.1007/978-1-4020-6359-6\_357",
    pages = "303-304"
}

Exceptional fossil specimens with preserved soft parts from the Maotianshan Shale (ca 520 Myr ago) and the Burgess Shale (505 Myr ago) biotas indicate that the worldwide distributed bivalved arthropod Isoxys was probably a non-benthic visual predator. New lines of evidence come from the functional morphology of its powerful prehensile frontal appendages that, combined with large spherical eyes, are thought to have played a key role in the recognition and capture of swimming or epibenthic prey. The swimming and steering of this arthropod was achieved by the beating of multiple setose exopods and a flap-like telson. The appendage morphology of Isoxys indicates possible phylogenetical relationships with the megacheirans, a widespread group of assumed predator arthropods characterized by a pre-oral 'great appendage'. Evidence from functional morphology and taphonomy suggests that Isoxys was able to migrate through the water column and was possibly exploiting hyperbenthic niches for food. Although certainly not unique, the case of Isoxys supports the idea that off-bottom animal interactions such as predation, associated with complex feeding strategies and behaviours (e.g. vertical migration and hunting) were established by the Early Cambrian. It also suggests that a prototype of a pelagic food chain had already started to build-up at least in the lower levels of the water column.

@article{doi101098rspb20090361,
    author = "Vannier, Jean and García‐Bellido, Diego C. and Hu, Shixue and Chen, A.-L.",
    title = "Arthropod visual predators in the early pelagic ecosystem: evidence from the Burgess Shale and Chengjiang biotas",
    year = "2009",
    journal = "Proceedings of the Royal Society B Biological Sciences",
    abstract = "Exceptional fossil specimens with preserved soft parts from the Maotianshan Shale (ca 520 Myr ago) and the Burgess Shale (505 Myr ago) biotas indicate that the worldwide distributed bivalved arthropod Isoxys was probably a non-benthic visual predator. New lines of evidence come from the functional morphology of its powerful prehensile frontal appendages that, combined with large spherical eyes, are thought to have played a key role in the recognition and capture of swimming or epibenthic prey. The swimming and steering of this arthropod was achieved by the beating of multiple setose exopods and a flap-like telson. The appendage morphology of Isoxys indicates possible phylogenetical relationships with the megacheirans, a widespread group of assumed predator arthropods characterized by a pre-oral 'great appendage'. Evidence from functional morphology and taphonomy suggests that Isoxys was able to migrate through the water column and was possibly exploiting hyperbenthic niches for food. Although certainly not unique, the case of Isoxys supports the idea that off-bottom animal interactions such as predation, associated with complex feeding strategies and behaviours (e.g. vertical migration and hunting) were established by the Early Cambrian. It also suggests that a prototype of a pelagic food chain had already started to build-up at least in the lower levels of the water column.",
    url = "https://doi.org/10.1098/rspb.2009.0361",
    doi = "10.1098/rspb.2009.0361",
    openalex = "W2140809040",
    references = "briggs1994decay, doi101016b9780444594259000196, doi101038417271a, doi10103846965, doi101038nature01264, doi101111j14754983200700649x, doi101111j14754983200900914x, doi10182618200374874199301, doi101826182003769311997, doi104202app20090024, doi105860choice416546, openalexw3127114020, openalexw3217097258"
}

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"
}

As the largest predators of the Cambrian seas, the anomalocaridids had an important impact in structuring the first complex marine animal communities, but many aspects of anomalocaridid morphology, diversity, ecology, and affinity remain unclear owing to a paucity of specimens. Here we describe the anomalocaridid Hurdia, based on several hundred specimens from the Burgess Shale in Canada. Hurdia possesses a general body architecture similar to those of Anomalocaris and Laggania, including the presence of exceptionally well-preserved gills, but differs from those anomalocaridids by possessing a prominent anterior carapace structure. These features amplify and clarify the diversity of known anomalocaridid morphology and provide insight into the origins of important arthropod features, such as the head shield and respiratory exites.

@article{doi101126science1169514,
    author = "Daley, Allison C. and Budd, Graham E. and Caron, Jean‐Bernard and Edgecombe, Gregory D. and Collins, Desmond",
    title = "The Burgess Shale Anomalocaridid Hurdia and Its Significance for Early Euarthropod Evolution",
    year = "2009",
    journal = "Science",
    abstract = "As the largest predators of the Cambrian seas, the anomalocaridids had an important impact in structuring the first complex marine animal communities, but many aspects of anomalocaridid morphology, diversity, ecology, and affinity remain unclear owing to a paucity of specimens. Here we describe the anomalocaridid Hurdia, based on several hundred specimens from the Burgess Shale in Canada. Hurdia possesses a general body architecture similar to those of Anomalocaris and Laggania, including the presence of exceptionally well-preserved gills, but differs from those anomalocaridids by possessing a prominent anterior carapace structure. These features amplify and clarify the diversity of known anomalocaridid morphology and provide insight into the origins of important arthropod features, such as the head shield and respiratory exites.",
    url = "https://doi.org/10.1126/science.1169514",
    doi = "10.1126/science.1169514",
    openalex = "W2058839077",
    references = "doi101016jpalaeo200705023, doi101017s0022336000023362, doi101017s1464793103006274, doi101038417271a, doi10108000241160410004764, doi10108011035899509546213, doi101098rstb19850096, doi101111j150239311996tb01831x, doi1016660022336020030770674ansftp20co2, doi101666060861, doi105281zenodo16273729, doi105281zenodo16490103"
}

More than forty specimens from the middle Cambrian Burgess Shale reveal the detailed anatomy of Isoxys, a worldwide distributed bivalved arthropod represented here by two species, namely Isoxys acutangulus and Isoxys longissimus. I. acutangulus had a non-mineralized headshield with lateral pleural folds (= "valves" of previous authors) that covered the animal's body almost entirely, large frontal spherical eyes and a pair of uniramous prehensile appendages bearing stout spiny outgrowths along their anterior margins. The 13 following appendages had a uniform biramous design-i.e., a short endopod and a paddle-like exopod fringed with marginal setae with a probable natatory function. The trunk ended with a flap-like telson that protruded beyond the posterior margin of the headshield. The gut of I. acutangulus was tube-like, running from mouth to telson, and was flanked with numerous 3D-preserved bulbous, paired features interpreted as digestive glands. The appendage design of I. acutangulus indicates that the animal was a swimmer and a visual predator living off-bottom. The general anatomy of Isoxys longissimus was similar to that of I. acutangulus although less information is available on the exact shape of its appendages and visual organs. I. longissimus is characterized by extremely long anterior and posterior spines. There are now seven Isoxys species known with soft-part preservation, I. acutangulus, I. longissimus from the Burgess Shale, I. auritus and I. curvirostratus from the Maotianshan Shale of China, I. communis and I. glaessneri from the Emu Bay Shale of Australia and I. volucris from Sirius Passet in Greenland. The frontal appendages of Isoxys strongly resemble those of other Cambrian arthropods, characterized by a single pair of "great appendages" with a shared prehensile function yet some variability in length and shape.

@article{doi104202app20090024,
    author = "García‐Bellido, Diego C. and Vannier, Jean and Collins, Desmond",
    title = "Soft-Part Preservation in two Species of the Arthropod Isoxys from the Middle Cambrian Burgess Shale of British Columbia, Canada",
    year = "2009",
    journal = "Acta Palaeontologica Polonica",
    abstract = {More than forty specimens from the middle Cambrian Burgess Shale reveal the detailed anatomy of Isoxys, a worldwide distributed bivalved arthropod represented here by two species, namely Isoxys acutangulus and Isoxys longissimus. I. acutangulus had a non-mineralized headshield with lateral pleural folds (= "valves" of previous authors) that covered the animal's body almost entirely, large frontal spherical eyes and a pair of uniramous prehensile appendages bearing stout spiny outgrowths along their anterior margins. The 13 following appendages had a uniform biramous design-i.e., a short endopod and a paddle-like exopod fringed with marginal setae with a probable natatory function. The trunk ended with a flap-like telson that protruded beyond the posterior margin of the headshield. The gut of I. acutangulus was tube-like, running from mouth to telson, and was flanked with numerous 3D-preserved bulbous, paired features interpreted as digestive glands. The appendage design of I. acutangulus indicates that the animal was a swimmer and a visual predator living off-bottom. The general anatomy of Isoxys longissimus was similar to that of I. acutangulus although less information is available on the exact shape of its appendages and visual organs. I. longissimus is characterized by extremely long anterior and posterior spines. There are now seven Isoxys species known with soft-part preservation, I. acutangulus, I. longissimus from the Burgess Shale, I. auritus and I. curvirostratus from the Maotianshan Shale of China, I. communis and I. glaessneri from the Emu Bay Shale of Australia and I. volucris from Sirius Passet in Greenland. The frontal appendages of Isoxys strongly resemble those of other Cambrian arthropods, characterized by a single pair of "great appendages" with a shared prehensile function yet some variability in length and shape.},
    url = "https://doi.org/10.4202/app.2009.0024",
    doi = "10.4202/app.2009.0024",
    openalex = "W2151689260",
    references = "briggs1994decay, doi1010160016703782903015, doi101038114085a0, doi10108000241160410004764, doi101111j14754983200900914x, doi1016660094837320020280155lgatio20co2, doi101826182003769311997, doi105860choice416546, openalexw2754161204, openalexw3127114020"
}

Stein, Martin (2010): A new arthropod from the Early Cambrian of North Greenland, with a 'great appendage'-like antennula. Zoological Journal of the Linnean Society 158 (3): 477-500, DOI: 10.1111/j.1096-3642.2009.00562.x, URL: http://dx.doi.org/10.1111/j.1096-3642.2009.00562.x

@article{doi101111j10963642200900562x,
    author = "Stein, Martin",
    title = "A new arthropod from the Early Cambrian of North Greenland, with a ‘great appendage’-like antennula",
    year = "2010",
    journal = "Zoological Journal of the Linnean Society",
    abstract = "Stein, Martin (2010): A new arthropod from the Early Cambrian of North Greenland, with a 'great appendage'-like antennula. Zoological Journal of the Linnean Society 158 (3): 477-500, DOI: 10.1111/j.1096-3642.2009.00562.x, URL: http://dx.doi.org/10.1111/j.1096-3642.2009.00562.x",
    url = "https://doi.org/10.1111/j.1096-3642.2009.00562.x",
    doi = "10.1111/j.1096-3642.2009.00562.x",
    openalex = "W1783894762",
    references = "doi101007s0042700600854, doi101038417271a, doi10108000241160410004764, doi101098rstb19950029, doi1011111475498300229, doi101111j14754983200700649x, doi1016660094837320020280155lgatio20co2, doi10182618200374874199301, doi101826182003769311997, doi1023072992562, doi104095103458, doi105860choice416546, openalexw2240758963"
}

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"
}

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"
}

Exceptionally preserved fossil biotas of the Burgess Shale and a handful of other similar Cambrian deposits provide rare but critical insights into the early diversification of animals. The extraordinary preservation of labile tissues in these geographically widespread but temporally restricted soft-bodied fossil assemblages has remained enigmatic since Walcott's initial discovery in 1909. Here, we demonstrate the mechanism of Burgess Shale-type preservation using sedimentologic and geochemical data from the Chengjiang, Burgess Shale, and five other principal Burgess Shale-type deposits. Sulfur isotope evidence from sedimentary pyrites reveals that the exquisite fossilization of organic remains as carbonaceous compressions resulted from early inhibition of microbial activity in the sediments by means of oxidant deprivation. Low sulfate concentrations in the global ocean and low-oxygen bottom water conditions at the sites of deposition resulted in reduced oxidant availability. Subsequently, rapid entombment of fossils in fine-grained sediments and early sealing of sediments by pervasive carbonate cements at bed tops restricted oxidant flux into the sediments. A permeability barrier, provided by bed-capping cements that were emplaced at the seafloor, is a feature that is shared among Burgess Shale-type deposits, and resulted from the unusually high alkalinity of Cambrian oceans. Thus, Burgess Shale-type preservation of soft-bodied fossil assemblages worldwide was promoted by unique aspects of early Paleozoic seawater chemistry that strongly impacted sediment diagenesis, providing a fundamentally unique record of the immediate aftermath of the "Cambrian explosion."

@article{doi101073pnas1111784109,
    author = "Gaines, Robert R. and Hammarlund, Emma U. and Hou, Xianguang and Qi, Changshi and Gabbott, Sarah E. and Zhao, Yuanlong and Peng, Jin and Canfield, Donald E.",
    title = "Mechanism for Burgess Shale-type preservation",
    year = "2012",
    journal = "Proceedings of the National Academy of Sciences",
    abstract = {Exceptionally preserved fossil biotas of the Burgess Shale and a handful of other similar Cambrian deposits provide rare but critical insights into the early diversification of animals. The extraordinary preservation of labile tissues in these geographically widespread but temporally restricted soft-bodied fossil assemblages has remained enigmatic since Walcott's initial discovery in 1909. Here, we demonstrate the mechanism of Burgess Shale-type preservation using sedimentologic and geochemical data from the Chengjiang, Burgess Shale, and five other principal Burgess Shale-type deposits. Sulfur isotope evidence from sedimentary pyrites reveals that the exquisite fossilization of organic remains as carbonaceous compressions resulted from early inhibition of microbial activity in the sediments by means of oxidant deprivation. Low sulfate concentrations in the global ocean and low-oxygen bottom water conditions at the sites of deposition resulted in reduced oxidant availability. Subsequently, rapid entombment of fossils in fine-grained sediments and early sealing of sediments by pervasive carbonate cements at bed tops restricted oxidant flux into the sediments. A permeability barrier, provided by bed-capping cements that were emplaced at the seafloor, is a feature that is shared among Burgess Shale-type deposits, and resulted from the unusually high alkalinity of Cambrian oceans. Thus, Burgess Shale-type preservation of soft-bodied fossil assemblages worldwide was promoted by unique aspects of early Paleozoic seawater chemistry that strongly impacted sediment diagenesis, providing a fundamentally unique record of the immediate aftermath of the "Cambrian explosion."},
    url = "https://doi.org/10.1073/pnas.1111784109",
    doi = "10.1073/pnas.1111784109",
    openalex = "W2122986069",
    references = "briggs1994decay, doi1010160009254194900612, doi1010160016703779900954, doi101016jpalaeo200407034, doi101016s0016703700005846, doi101038296643a0, doi101038nature09700, doi101038nature10969, doi101073pnas0902037106, doi101073pnas1011287107, doi101098rstb19810033, doi101111j150239311995tb01587x, doi101126science1135013, doi101126science1154499, doi1011300091761319950231079isbapo23co2, doi101130g206401, doi101130g24961a1, doi1016660094837320020280155lgatio20co2, doi102475ajs2929659"
}

Extant arthropods are diverse and ubiquitous, forming a major constituent of most modern ecosystems. Evidence from early Palaeozoic Konservat Lagerstätten indicates that this has been the case since the Cambrian. Despite this, the details of arthropod origins remain obscure, although most hypotheses regard the first arthropods as benthic predators or scavengers such as the fuxianhuiids or megacheirans ('great-appendage' arthropods). Here, we describe a new arthropod from the Tulip Beds locality of the Burgess Shale Formation (Cambrian, series 3, stage 5) that possesses a weakly sclerotized thorax with filamentous appendages, encased in a bivalved carapace, and a strongly sclerotized, elongate abdomen and telson. A cladistic analysis resolved this taxon as the basal-most member of a paraphyletic grade of nekto-benthic forms with bivalved carapaces. This grade occurs at the base of Arthropoda (panarthropods with arthropodized trunk limbs) and suggests that arthrodization (sclerotization and jointing of the exoskeleton) evolved to facilitate swimming. Predatory and fully benthic habits evolved later in the euarthropod stem-lineage and are plesiomorphically retained in pycnogonids (sea spiders) and euchelicerates (horseshoe crabs and arachnids).

@article{doi101098rspb20121958,
    author = "Legg, David and Sutton, Mark D. and Edgecombe, Gregory D. and Caron, Jean‐Bernard",
    title = "Cambrian bivalved arthropod reveals origin of arthrodization",
    year = "2012",
    journal = "Proceedings of the Royal Society B Biological Sciences",
    abstract = "Extant arthropods are diverse and ubiquitous, forming a major constituent of most modern ecosystems. Evidence from early Palaeozoic Konservat Lagerstätten indicates that this has been the case since the Cambrian. Despite this, the details of arthropod origins remain obscure, although most hypotheses regard the first arthropods as benthic predators or scavengers such as the fuxianhuiids or megacheirans ('great-appendage' arthropods). Here, we describe a new arthropod from the Tulip Beds locality of the Burgess Shale Formation (Cambrian, series 3, stage 5) that possesses a weakly sclerotized thorax with filamentous appendages, encased in a bivalved carapace, and a strongly sclerotized, elongate abdomen and telson. A cladistic analysis resolved this taxon as the basal-most member of a paraphyletic grade of nekto-benthic forms with bivalved carapaces. This grade occurs at the base of Arthropoda (panarthropods with arthropodized trunk limbs) and suggests that arthrodization (sclerotization and jointing of the exoskeleton) evolved to facilitate swimming. Predatory and fully benthic habits evolved later in the euarthropod stem-lineage and are plesiomorphically retained in pycnogonids (sea spiders) and euchelicerates (horseshoe crabs and arachnids).",
    url = "https://doi.org/10.1098/rspb.2012.1958",
    doi = "10.1098/rspb.2012.1958",
    openalex = "W2128120004",
    references = "doi101038417271a, doi10108011035890809452772, doi101098rspb20100590, doi101098rstb19810007, doi101111j109600311993tb00209x, doi101111j109600311999tb00277x, doi101111j109600311999tb00278x, doi101111j10960031200800217x, doi101371journalpone0029233, doi101371journalpone0035495, doi101826182003769311997, doi1023073515467, doi105860choice416546"
}

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"
}

@incollection{russell2012arthropods,
    author = "Russell, R.C.",
    title = "Arthropods",
    year = "2012",
    booktitle = "Medical Microbiology",
    url = "https://doi.org/10.1016/b978-0-7020-4089-4.00078-0",
    doi = "10.1016/b978-0-7020-4089-4.00078-0",
    pages = "667-675"
}

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"
}

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"
}

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"
}

Harry Whittington's 1975 monograph on Opabinia was the first to highlight how some of the Burgess Shale animals differ markedly from those that populate today's oceans. Categorized by Stephen J. Gould as a 'weird wonder' (Wonderful life, 1989) Opabinia, together with other unusual Burgess Shale fossils, stimulated ongoing debates about the early evolution of the major animal groups and the nature of the Cambrian explosion. The subsequent discovery of a number of other exceptionally preserved fossil faunas of Cambrian and early Ordovician age has significantly augmented the information available on this critical interval in the history of life. Although Opabinia initially defied assignment to any group of modern animals, it is now interpreted as lying below anomalocaridids on the stem leading to the living arthropods. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society.

@article{doi101098rstb20140313,
    author = "Briggs, Derek E G",
    title = "Extraordinary fossils reveal the nature of Cambrian life: a commentary on Whittington (1975) 'The enigmatic animal Opabinia regalis, Middle Cambrian, Burgess Shale, British Columbia'.",
    year = "2015",
    journal = "Philosophical transactions of the Royal Society of London. Series B, Biological sciences",
    abstract = "Harry Whittington's 1975 monograph on Opabinia was the first to highlight how some of the Burgess Shale animals differ markedly from those that populate today's oceans. Categorized by Stephen J. Gould as a 'weird wonder' (Wonderful life, 1989) Opabinia, together with other unusual Burgess Shale fossils, stimulated ongoing debates about the early evolution of the major animal groups and the nature of the Cambrian explosion. The subsequent discovery of a number of other exceptionally preserved fossil faunas of Cambrian and early Ordovician age has significantly augmented the information available on this critical interval in the history of life. Although Opabinia initially defied assignment to any group of modern animals, it is now interpreted as lying below anomalocaridids on the stem leading to the living arthropods. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society.",
    url = "https://pmc.ncbi.nlm.nih.gov/articles/PMC4360120/",
    doi = "10.1098/rstb.2014.0313",
    openalex = "W1981460678",
    pmcid = "PMC4360120",
    pmid = "25750235",
    references = "doi101017s009483730001263x, doi101038nature09038, doi101038nature10689, doi101073pnas1111784109, doi101111j150239311995tb01587x, doi101126science1206375, doi101130g24961a1, doi105860choice273873, openalexw2754161204, openalexw3127114020"
}

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"
}

@incollection{crossref2016arthropods,
    title = "Arthropods",
    year = "2016",
    booktitle = "The Marine World",
    url = "https://doi.org/10.1515/9780691232447-018",
    doi = "10.1515/9780691232447-018",
    pages = "258-283"
}

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"
}

The biology of the American horseshoe crab, Limulus polyphemus, is well documented-including its dietary habits, particularly the ability to crush shell with gnathobasic walking appendages-but virtually nothing is known about the feeding biomechanics of this iconic arthropod. Limulus polyphemus is also considered the archetypal functional analogue of various extinct groups with serial gnathobasic appendages, including eurypterids, trilobites and other early arthropods, especially Sidneyia inexpectans from the mid-Cambrian (508 Myr) Burgess Shale of Canada. Exceptionally preserved specimens of S. inexpectans show evidence suggestive of durophagous (shell-crushing) tendencies-including thick gnathobasic spine cuticle and shelly gut contents-but the masticatory capabilities of this fossil species have yet to be compared with modern durophagous arthropods. Here, we use advanced computational techniques, specifically a unique application of 3D finite-element analysis (FEA), to model the feeding mechanics of L. polyphemus and S. inexpectans: the first such analyses of a modern horseshoe crab and a fossil arthropod. Results show that mechanical performance of the feeding appendages in both arthropods is remarkably similar, suggesting that S. inexpectans had similar shell-crushing capabilities to L. polyphemus This biomechanical solution to processing shelly food therefore has a history extending over 500 Myr, arising soon after the first shell-bearing animals. Arrival of durophagous predators during the early phase of animal evolution undoubtedly fuelled the Cambrian 'arms race' that involved a rapid increase in diversity, disparity and abundance of biomineralized prey species.

@article{doi101098rspb20181935,
    author = "Bicknell, Russell D. C. and Ledogar, Justin A. and Wroe, Stephen and Gutzler, Benjamin C. and Watson, Winsor H. and Paterson, John R.",
    title = "Computational biomechanical analyses demonstrate similar shell-crushing abilities in modern and ancient arthropods",
    year = "2018",
    journal = "Proceedings of the Royal Society B Biological Sciences",
    abstract = "The biology of the American horseshoe crab, Limulus polyphemus, is well documented-including its dietary habits, particularly the ability to crush shell with gnathobasic walking appendages-but virtually nothing is known about the feeding biomechanics of this iconic arthropod. Limulus polyphemus is also considered the archetypal functional analogue of various extinct groups with serial gnathobasic appendages, including eurypterids, trilobites and other early arthropods, especially Sidneyia inexpectans from the mid-Cambrian (508 Myr) Burgess Shale of Canada. Exceptionally preserved specimens of S. inexpectans show evidence suggestive of durophagous (shell-crushing) tendencies-including thick gnathobasic spine cuticle and shelly gut contents-but the masticatory capabilities of this fossil species have yet to be compared with modern durophagous arthropods. Here, we use advanced computational techniques, specifically a unique application of 3D finite-element analysis (FEA), to model the feeding mechanics of L. polyphemus and S. inexpectans: the first such analyses of a modern horseshoe crab and a fossil arthropod. Results show that mechanical performance of the feeding appendages in both arthropods is remarkably similar, suggesting that S. inexpectans had similar shell-crushing capabilities to L. polyphemus This biomechanical solution to processing shelly food therefore has a history extending over 500 Myr, arising soon after the first shell-bearing animals. Arrival of durophagous predators during the early phase of animal evolution undoubtedly fuelled the Cambrian 'arms race' that involved a rapid increase in diversity, disparity and abundance of biomineralized prey species.",
    url = "https://doi.org/10.1098/rspb.2018.1935",
    doi = "10.1098/rspb.2018.1935",
    openalex = "W2898586552",
    references = "doi101016jasd201509003, doi101016jasd201712001, doi101111brv12365"
}

The trilobite Redlichia Cossmann, 1902 Cossmann, M. 1902. Rectification de la nomenclature. Revista Critica Paleozoologie, 16, 52. [Google Scholar] is an abundant element of the lower Cambrian (Series 2, Stage 4) Emu Bay Shale (EBS) Konservat-Lagerstätte on Kangaroo Island, South Australia. Well-preserved, fully articulated specimens from this deposit are known to reach lengths of up to 25 cm, representing one of the largest known Cambrian trilobites. Until now, all Redlichia specimens from the EBS have been referred to Redlichia takooensis Lu, 1950 Lu, Y.-H. 1950. On the genus Redlichia with description of its new species. Geological Review, 15, 157–170. [In Chinese.] [Google Scholar], a species originally described from South China. Previous work recognized considerable differences in exoskeletal morphology among specimens of varying sizes, which was attributed to ontogeny. However, close examination of a large collection of recently acquired specimens shows that this variation actually represents two distinct morphs, interpreted here as separate species: R. takooensis, and a large, new species, Redlichia rex sp. nov. An analysis of morphological variation in holaspides (‘adults’) of the more common R. takooensis reveals considerable ontogenetic change occurred even during this later phase of growth. Some specimens of both Redlichia species from the EBS also exhibit exceptionally preserved soft-part anatomy, particularly the antennae and biramous appendages. Here, appendages (antenniform and biramous) and digestive structures are described, and biramous appendage reconstructions of R. rex sp. nov. are presented, which show a striking resemblance to some early Cambrian trilobites from South China. In particular, R. rex has a tripartite exopodite, as well as a dorsoventrally deep protopodite with gnathobasic spines used to shred or crush food items. Based on recent phylogenetic analyses, it is possible that an exopodite with tripartite subdivisions represents the plesiomorphic condition for Artiopoda (trilobites and kin). The digestive system of R. takooensis exhibits a series of paired digestive glands in the cephalon and anterior thorax, similar to those described for a number of other Cambrian and Ordovician trilobites.http://zoobank.org/urn:lsid:zoobank.org:pub:507BEAFC-4AFA-43F4-A5C4-49E4B58C658E

@article{doi1010801477201920191605411,
    author = "Holmes, James D. and Paterson, John R. and García‐Bellido, Diego C.",
    title = "The trilobite Redlichia from the lower Cambrian Emu Bay Shale Konservat-Lagerstätte of South Australia: systematics, ontogeny and soft-part anatomy",
    year = "2019",
    journal = "Journal of Systematic Palaeontology",
    abstract = "The trilobite Redlichia Cossmann, 1902 Cossmann, M. 1902. Rectification de la nomenclature. Revista Critica Paleozoologie, 16, 52. [Google Scholar] is an abundant element of the lower Cambrian (Series 2, Stage 4) Emu Bay Shale (EBS) Konservat-Lagerstätte on Kangaroo Island, South Australia. Well-preserved, fully articulated specimens from this deposit are known to reach lengths of up to 25 cm, representing one of the largest known Cambrian trilobites. Until now, all Redlichia specimens from the EBS have been referred to Redlichia takooensis Lu, 1950 Lu, Y.-H. 1950. On the genus Redlichia with description of its new species. Geological Review, 15, 157–170. [In Chinese.] [Google Scholar], a species originally described from South China. Previous work recognized considerable differences in exoskeletal morphology among specimens of varying sizes, which was attributed to ontogeny. However, close examination of a large collection of recently acquired specimens shows that this variation actually represents two distinct morphs, interpreted here as separate species: R. takooensis, and a large, new species, Redlichia rex sp. nov. An analysis of morphological variation in holaspides (‘adults’) of the more common R. takooensis reveals considerable ontogenetic change occurred even during this later phase of growth. Some specimens of both Redlichia species from the EBS also exhibit exceptionally preserved soft-part anatomy, particularly the antennae and biramous appendages. Here, appendages (antenniform and biramous) and digestive structures are described, and biramous appendage reconstructions of R. rex sp. nov. are presented, which show a striking resemblance to some early Cambrian trilobites from South China. In particular, R. rex has a tripartite exopodite, as well as a dorsoventrally deep protopodite with gnathobasic spines used to shred or crush food items. Based on recent phylogenetic analyses, it is possible that an exopodite with tripartite subdivisions represents the plesiomorphic condition for Artiopoda (trilobites and kin). The digestive system of R. takooensis exhibits a series of paired digestive glands in the cephalon and anterior thorax, similar to those described for a number of other Cambrian and Ordovician trilobites.http://zoobank.org/urn:lsid:zoobank.org:pub:507BEAFC-4AFA-43F4-A5C4-49E4B58C658E",
    url = "https://doi.org/10.1080/14772019.2019.1605411",
    doi = "10.1080/14772019.2019.1605411",
    openalex = "W2951355339",
    references = "doi101016jasd201712001, doi10108003115510508619300, doi101080147720192013852903, doi101144jgs2015083, doi104202app20090024"
}

The origin of the arthropod carapace, an enlargement of cephalic tergites, can be traced back to the Cambrian period. However, its disparity and evolution are still not fully understood. Here, we describe a new 'bivalved' arthropod, Fibulacaris nereidis gen. et sp. nov., based on 102 specimens from the middle Cambrian (Wuliuan Stage) Burgess Shale, Marble Canyon area in British Columbia's Kootenay National Park, Canada. The laterally compressed carapace covers most of the body. It is fused dorsally and merges anteriorly into a conspicuous postero-ventrally recurved rostrum as long as the carapace and positioned between a pair of backwards-facing pedunculate eyes. The body is homonomous, with approximately 40 weakly sclerotized segments bearing biramous legs with elongate endopods, and ends in a pair of small flap-like caudal rami. Fibulacaris nereidis is interpreted as a suspension feeder possibly swimming inverted, in a potential case of convergence with some branchiopods. A Bayesian phylogenetic analysis places it within a group closely related to the extinct Hymenocarina. Fibulacaris nereidis is unique in its carapace morphology and overall widens the ecological disparity of Cambrian arthropods and suggests that the evolution of a 'bivalved' carapace and an upside-down lifestyle may have occurred early in stem-group crustaceans.

@article{doi101098rsos191350,
    author = "Izquierdo-López, Alejandro and Caron, Jean-Bernard",
    title = "A possible case of inverted lifestyle in a new bivalved arthropod from the Burgess Shale.",
    year = "2019",
    journal = "Royal Society open science",
    abstract = "The origin of the arthropod carapace, an enlargement of cephalic tergites, can be traced back to the Cambrian period. However, its disparity and evolution are still not fully understood. Here, we describe a new 'bivalved' arthropod, Fibulacaris nereidis gen. et sp. nov., based on 102 specimens from the middle Cambrian (Wuliuan Stage) Burgess Shale, Marble Canyon area in British Columbia's Kootenay National Park, Canada. The laterally compressed carapace covers most of the body. It is fused dorsally and merges anteriorly into a conspicuous postero-ventrally recurved rostrum as long as the carapace and positioned between a pair of backwards-facing pedunculate eyes. The body is homonomous, with approximately 40 weakly sclerotized segments bearing biramous legs with elongate endopods, and ends in a pair of small flap-like caudal rami. Fibulacaris nereidis is interpreted as a suspension feeder possibly swimming inverted, in a potential case of convergence with some branchiopods. A Bayesian phylogenetic analysis places it within a group closely related to the extinct Hymenocarina. Fibulacaris nereidis is unique in its carapace morphology and overall widens the ecological disparity of Cambrian arthropods and suggests that the evolution of a 'bivalved' carapace and an upside-down lifestyle may have occurred early in stem-group crustaceans.",
    url = "https://pmc.ncbi.nlm.nih.gov/articles/PMC6894550/",
    doi = "10.1098/rsos.191350",
    openalex = "W2987553491",
    pmcid = "PMC6894550",
    pmid = "31827867",
    references = "doi101016jcub201705040, doi101038nature08742, doi101086415511, doi101093oxfordjournalsmolbeva004133, doi101093sysbiosys029, doi101098rspb20100590, doi101098rstb19680017, doi1016660094837320020280155lgatio20co2, doi10182618200374874199301"
}

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"
}

@incollection{crossref2021arthropods,
    title = "Arthropods",
    year = "2021",
    booktitle = "A Photographic Guide to Seashore Life in the North Atlantic",
    url = "https://doi.org/10.2307/j.ctv1vwbtss.10",
    doi = "10.2307/j.ctv1vwbtss.10",
    pages = "110-127"
}

Abstract Cambrian bivalved arthropods are a polyphyletic group of carapace‐bearing arthropods that includes stem euarthropods, stem mandibulates and crustaceans. Here, we describe Pakucaris apatis gen. et sp. nov., a new stem mandibulate bivalved arthropod from the middle Cambrian (Wuliuan Stage) Burgess Shale (Marble Canyon, Kootenay National Park, British Columbia, Canada). Two morphotypes of this small arthropod (11.6–26.6 mm long) are recognized, which differ mainly in their size and number of segments, possibly reflecting sexual dimorphism or different anamorphic stages. The carapace presents a dorsal crest extending anteriorly into a small recurved rostrum and two anterolateral processes. Around 20% of the posteriormost body segments and limbs are covered by a large spine‐bearing shield. The head bears a pair of eyes, a possible pair of unsegmented appendicular projections and two pairs of segmented appendages. The thorax is multisegmented, homonomous, with weakly sclerotized segments bearing biramous limbs, composed of a stenopodous endopod with c. 20 podomeres and a paddle‐shaped exopod. Pakucaris is interpreted as a nektobenthic suspension feeder. Bayesian phylogenetic analysis implies a position within Hymenocarina as stem mandibulates. The posterior shield is regarded as a pygidium, and represents a case of morphofunctional convergent evolution between mandibulates, artiopodans and mollisoniids. Furthermore, Pakucaris adds to a growing number of pygidium‐bearing arthropods, potentially hinting at a common developmental pattern across early arthropod evolution. This study not only increases our understanding of the early evolution of mandibulates, but also illustrates a unique case of early evolutionary convergence during the Cambrian Explosion.

@article{doi101002spp21366,
    author = "Izquierdo‐López, Alejandro and Caron, Jean‐Bernard",
    title = "A Burgess Shale mandibulate arthropod with a pygidium: a case of convergent evolution",
    year = "2021",
    journal = "Papers in Palaeontology",
    abstract = "Abstract Cambrian bivalved arthropods are a polyphyletic group of carapace‐bearing arthropods that includes stem euarthropods, stem mandibulates and crustaceans. Here, we describe Pakucaris apatis gen. et sp. nov., a new stem mandibulate bivalved arthropod from the middle Cambrian (Wuliuan Stage) Burgess Shale (Marble Canyon, Kootenay National Park, British Columbia, Canada). Two morphotypes of this small arthropod (11.6–26.6 mm long) are recognized, which differ mainly in their size and number of segments, possibly reflecting sexual dimorphism or different anamorphic stages. The carapace presents a dorsal crest extending anteriorly into a small recurved rostrum and two anterolateral processes. Around 20\% of the posteriormost body segments and limbs are covered by a large spine‐bearing shield. The head bears a pair of eyes, a possible pair of unsegmented appendicular projections and two pairs of segmented appendages. The thorax is multisegmented, homonomous, with weakly sclerotized segments bearing biramous limbs, composed of a stenopodous endopod with c. 20 podomeres and a paddle‐shaped exopod. Pakucaris is interpreted as a nektobenthic suspension feeder. Bayesian phylogenetic analysis implies a position within Hymenocarina as stem mandibulates. The posterior shield is regarded as a pygidium, and represents a case of morphofunctional convergent evolution between mandibulates, artiopodans and mollisoniids. Furthermore, Pakucaris adds to a growing number of pygidium‐bearing arthropods, potentially hinting at a common developmental pattern across early arthropod evolution. This study not only increases our understanding of the early evolution of mandibulates, but also illustrates a unique case of early evolutionary convergence during the Cambrian Explosion.",
    url = "https://doi.org/10.1002/spp2.1366",
    doi = "10.1002/spp2.1366",
    openalex = "W3171801394",
    references = "doi101016jcub202002054, doi101098rsos191350"
}

Fossil Lagerstätten similar to the Cambrian Burgess Shale have a crucial role in revealing the origin and early evolution of arthropods. Tuzoiidae, one of the most important groups of bivalved arthropods, occupied an important ecological niche in the Cambrian marine ecosystem. We describe a new taxon, Duplapex anima gen. et. sp. nov., in the Family Tuzoiidae on the basis of four exceptionally preserved specimens from the early Cambrian (Stage 3) Qingjiang biota of Hubei, South China. Duplapex is characterized by an ornamented bivalved carapace, a ventral notch and doublure spine on the valve and a pair of compound eyes connected by fleshy annulated eye stalks. Despite having an unusual morphology for the group, the new taxon is recognized as a tuzoiid arthropod and indicates that these problematic euarthropods had a greater degree of morphological disparity than previously considered. D. anima, as well as the newly reported Tuzoia. sp. from the Fandian biota, represent the oldest occurrence of Tuzoiidae, extending its stratigraphic range to Cambrian Stage 3 and expanding the palaeogeographical distribution of the group to the northern border of the Yangtze Platform. Thematic collection: This article is part of the Advances in the Cambrian Explosion collection available at: https://www.lyellcollection.org/cc/advances-cambrian-explosion

@article{doi101144jgs2020229,
    author = "Ma, Jiaxin and Lin, Weiliang and Liu, Cong and Sun, Ao and Wu, Yu and Wu, Yuheng and Fu, Dongjing",
    title = "A new bivalved arthropod from the Cambrian (Stage 3) Qingjiang biota expands the palaeogeographical distribution and increases the diversity of Tuzoiidae",
    year = "2021",
    journal = "Journal of the Geological Society",
    abstract = "Fossil Lagerstätten similar to the Cambrian Burgess Shale have a crucial role in revealing the origin and early evolution of arthropods. Tuzoiidae, one of the most important groups of bivalved arthropods, occupied an important ecological niche in the Cambrian marine ecosystem. We describe a new taxon, Duplapex anima gen. et. sp. nov., in the Family Tuzoiidae on the basis of four exceptionally preserved specimens from the early Cambrian (Stage 3) Qingjiang biota of Hubei, South China. Duplapex is characterized by an ornamented bivalved carapace, a ventral notch and doublure spine on the valve and a pair of compound eyes connected by fleshy annulated eye stalks. Despite having an unusual morphology for the group, the new taxon is recognized as a tuzoiid arthropod and indicates that these problematic euarthropods had a greater degree of morphological disparity than previously considered. D. anima, as well as the newly reported Tuzoia. sp. from the Fandian biota, represent the oldest occurrence of Tuzoiidae, extending its stratigraphic range to Cambrian Stage 3 and expanding the palaeogeographical distribution of the group to the northern border of the Yangtze Platform. Thematic collection: This article is part of the Advances in the Cambrian Explosion collection available at: https://www.lyellcollection.org/cc/advances-cambrian-explosion",
    url = "https://doi.org/10.1144/jgs2020-229",
    doi = "10.1144/jgs2020-229",
    openalex = "W3167122454",
    references = "doi101098rsos191350"
}

The origin of mandibulate arthropods can be traced back to the Cambrian period to several carapace-bearing arthropod groups, but their morphological diversity is still not well characterized. Here, we describe Balhuticaris voltae, a bivalved arthropod from the 506-million-year-old Burgess Shale (Marble Canyon, British Columbia, Canada). This species has an extremely elongated and multisegmented body bearing ca. 110 pairs of homonomous biramous limbs, the highest number among Cambrian arthropods, and, at 245 mm, it represents one of the largest Cambrian arthropods known. Its unusual carapace resembles an arch; it covers only the frontalmost section of the body but extends ventrally beyond the legs. Balhuticaris had a complex sensory system and was probably an active swimmer thanks to its powerful paddle-shaped exopods and a long and flexible body. Balhuticaris increases the ecological and functional diversity of bivalved arthropods and suggests that cases of gigantism occurred in more arthropod groups than previously recognized.

@article{doi101016jisci2022104675,
    author = "Izquierdo‐López, Alejandro and Caron, Jean‐Bernard",
    title = "Extreme multisegmentation in a giant bivalved arthropod from the Cambrian Burgess Shale",
    year = "2022",
    journal = "iScience",
    abstract = "The origin of mandibulate arthropods can be traced back to the Cambrian period to several carapace-bearing arthropod groups, but their morphological diversity is still not well characterized. Here, we describe Balhuticaris voltae, a bivalved arthropod from the 506-million-year-old Burgess Shale (Marble Canyon, British Columbia, Canada). This species has an extremely elongated and multisegmented body bearing ca. 110 pairs of homonomous biramous limbs, the highest number among Cambrian arthropods, and, at 245 mm, it represents one of the largest Cambrian arthropods known. Its unusual carapace resembles an arch; it covers only the frontalmost section of the body but extends ventrally beyond the legs. Balhuticaris had a complex sensory system and was probably an active swimmer thanks to its powerful paddle-shaped exopods and a long and flexible body. Balhuticaris increases the ecological and functional diversity of bivalved arthropods and suggests that cases of gigantism occurred in more arthropod groups than previously recognized.",
    url = "https://doi.org/10.1016/j.isci.2022.104675",
    doi = "10.1016/j.isci.2022.104675",
    openalex = "W4283454036",
    references = "doi101098rsos191350"
}

The origin of mandibulates, the hyperdiverse arthropod group that includes pancrustaceans and myriapods, dates back to the Cambrian. Bivalved arthropod groups such as hymenocarines have been argued to be early mandibulates, but many species are still poorly known, and their affinities remain uncertain. One of the most common and globally distributed Cambrian bivalved arthropods is Tuzoia. Originally described in 1912 from the Burgess Shale based on isolated carapaces, its full anatomy has remained largely unknown. Here, we describe new specimens of Tuzoia from the Canadian Burgess Shale (Wuliuan, Cambrian) showcasing exceptionally preserved soft tissues, allowing for the first comprehensive reconstruction of its anatomy, ecology and evolutionary affinities. The head bears antennae and differentiated cephalic appendages. The body is divided into a cephalothorax, a homonomous trunk bearing ca 10 pairs of legs with heptopodomerous endopods and enlarged basipods, and a tail fan with two pairs of caudal rami. These traits suggest that Tuzoia swam along the seafloor and used its spinose legs for predation or scavenging. Tuzoia is retrieved by a Bayesian phylogenetic analysis as an early mandibulate hymenocarine lineage, exemplifying the rapid diversification of this group in open marine environments during the Cambrian Explosion.

@article{doi101098rsos220933,
    author = "Izquierdo‐López, Alejandro and Caron, Jean‐Bernard",
    title = "The problematic Cambrian arthropod Tuzoia and the origin of mandibulates revisited",
    year = "2022",
    journal = "Royal Society Open Science",
    abstract = "The origin of mandibulates, the hyperdiverse arthropod group that includes pancrustaceans and myriapods, dates back to the Cambrian. Bivalved arthropod groups such as hymenocarines have been argued to be early mandibulates, but many species are still poorly known, and their affinities remain uncertain. One of the most common and globally distributed Cambrian bivalved arthropods is Tuzoia. Originally described in 1912 from the Burgess Shale based on isolated carapaces, its full anatomy has remained largely unknown. Here, we describe new specimens of Tuzoia from the Canadian Burgess Shale (Wuliuan, Cambrian) showcasing exceptionally preserved soft tissues, allowing for the first comprehensive reconstruction of its anatomy, ecology and evolutionary affinities. The head bears antennae and differentiated cephalic appendages. The body is divided into a cephalothorax, a homonomous trunk bearing ca 10 pairs of legs with heptopodomerous endopods and enlarged basipods, and a tail fan with two pairs of caudal rami. These traits suggest that Tuzoia swam along the seafloor and used its spinose legs for predation or scavenging. Tuzoia is retrieved by a Bayesian phylogenetic analysis as an early mandibulate hymenocarine lineage, exemplifying the rapid diversification of this group in open marine environments during the Cambrian Explosion.",
    url = "https://doi.org/10.1098/rsos.220933",
    doi = "10.1098/rsos.220933",
    openalex = "W4310803405",
    references = "doi101016jcub201904057, doi101017s1464793103006274, doi101038ncomms3485, doi101093bioinformaticsbtq706, doi101093bioinformaticsbty633, doi101093sysbiosys029, doi101093sysbiosyy032, doi101098rsos191350, doi101098rsos220933, doi101098rspb20100590, doi101098rstb20210034, doi1011112041210x12035, doi101111brv12864, doi1018637jssv056i13"
}

Abstract The Cambrian (Series 2, Stage 3) Qingjiang Lagerstätte of South China is one of the most diverse Burgess Shale‐type deposits around the world, yielding abundant non‐biomineralized fossils. Radiodonta, a taxonomically and ecologically diverse stem‐euarthropod group, has been generally thought to represent the largest consumers in early Palaeozoic marine ecosystems. Here we describe several new radiodont specimens from the Qingjiang Lagerstätte assigned to various groups, including Stanleycaris qingjiangensis sp. nov., a new type of hurdiid head carapace, one possible Hurdia carapace, and two partial appendages with uncertain affinities. These specimens not only extend the geographic and stratigraphic range of these taxa, they also illuminate the diversity of radiodonts (in particular hurdiids) in their early evolutionary history. Radiodont palaeobiogeographic patterns are visualized using network analysis. Laurentia and South China share many members at the genus level, Anomalocaris is the most cosmopolitan taxon, but most genera are endemic. Radiodonts show a high initial diversity that declines through the early Palaeozoic, enabling three diversification phases of radiodonts to be recognized: the thriving phase (Cambrian Series 2), declining phase (Cambrian Miaolingian) and terminal phase (Cambrian Furongian to Ordovician Floian).

@article{doi101002spp21583,
    author = "Wu, Yu and Pates, Stephen and Zhang, Mingjing and Lin, Weiliang and Ma, Jiaxin and Liu, Cong and Wu, Yuheng and Zhang, Xingliang and Fu, Dongjing",
    title = "Exceptionally preserved radiodont arthropods from the lower Cambrian (Stage 3) Qingjiang Lagerstätte of Hubei, South China and the biogeographic and diversification patterns of radiodonts",
    year = "2024",
    journal = "Papers in Palaeontology",
    abstract = "Abstract The Cambrian (Series 2, Stage 3) Qingjiang Lagerstätte of South China is one of the most diverse Burgess Shale‐type deposits around the world, yielding abundant non‐biomineralized fossils. Radiodonta, a taxonomically and ecologically diverse stem‐euarthropod group, has been generally thought to represent the largest consumers in early Palaeozoic marine ecosystems. Here we describe several new radiodont specimens from the Qingjiang Lagerstätte assigned to various groups, including Stanleycaris qingjiangensis sp. nov., a new type of hurdiid head carapace, one possible Hurdia carapace, and two partial appendages with uncertain affinities. These specimens not only extend the geographic and stratigraphic range of these taxa, they also illuminate the diversity of radiodonts (in particular hurdiids) in their early evolutionary history. Radiodont palaeobiogeographic patterns are visualized using network analysis. Laurentia and South China share many members at the genus level, Anomalocaris is the most cosmopolitan taxon, but most genera are endemic. Radiodonts show a high initial diversity that declines through the early Palaeozoic, enabling three diversification phases of radiodonts to be recognized: the thriving phase (Cambrian Series 2), declining phase (Cambrian Miaolingian) and terminal phase (Cambrian Furongian to Ordovician Floian).",
    url = "https://doi.org/10.1002/spp2.1583",
    doi = "10.1002/spp2.1583",
    openalex = "W4401789453",
    references = "doi101016jjseaes201702043, doi101098rsos191350, doi101098rsos220933, doi101098rspb20230638, doi103389feart20231160285"
}

@misc{crossrefNonearthropods,
    title = "ARTHROPODS",
    year = "None",
    booktitle = "Encyclopaedia Iranica Online",
    url = "https://doi.org/10.1163/2330-4804\_eiro\_com\_5842",
    doi = "10.1163/2330-4804\_eiro\_com\_5842"
}