Hell creek formation

Early studies of vertebrate and plant fossils in the San Juan Basin confirmed a late Cretaceous age for the Kirtland Shale and a Tertiary age for the Nacimiento Formation, but resulted in disagreement over the age of the intervening Ojo Alamo Sandstone. Dinosaur evidence indicated a late, but not latest, Cretaceous age, but fragmentary plant megafossils suggested a Tertiary age. Pollen and spore florules collected from within, above, and below the formation tend to confirm a Tertiary age and reflect the environmental changes that accompanied local uplift at the Cretaceous-Tertiary transition. The most significant ecologic change takes place at the base of the Ojo Alamo Sandstone with the appearance of many podocarpaceous and ulmacoues pollen. The most significant change in terms of common forms occurs between the basal Ojo Alamo florule and one collected from a shale unit in the middle of the formation. The basal florule has only four forms in common with the overlying or underlying florules and could be either Cretaceous of Paleocene. The middle florule, however, has nine forms in common with the overlying Nacimiento florules, suggesting Tertiary affinity. Middle Montanan dinosaur bones and fragments, which occur in a similar shale unit on the western side of the basin, may have been reworked or erroneously identified. Proteaceous grains and Tilia are the dominant dicotyledonous types in the Kirtland Shale florule. Conifers are absent. The florule from the base of the Ojo Alamo Sandstone contains more than 70% Podocarpus pollen, ulmaceous pollen, and several other probable upland types. The middle Ojo Alamo florule contains a mixture of probable upland and lowland forms, as does a florule from the base of the Nacimiento Formation. A florule in the lower part of the Nacimiento Formation is similar to the florule at the base. Ulmaceous pollen, Momipites, and Cupanieidites are the most persistent dicotyledonous types in these three florules. A florule from the uppermost part of the Lewis Shale is a northern equivalent of the Kirtland or lower Ojo Alamo florule but is very different because of a more coastal environment on the opposite shore of the Lewis Sea. The classification system used in this study employs a combination of extant, organ, and form genera arranged in a phylogenetic outline. Eight new genera, Bombacacipites, Brevicolporites, Confertisulcites, Intertriletes, Kurtzipites, Navisulcites, Rectosulcites, and Ulmoideipites, are established, and several others are validated. Of the 88 fossil descriptions, 39 are new species and four are descriptions of dinoflagellates and marine microfossils Incertae Sedis from the Lewis Shale.

@book{doi1058799m6,
    author = "Anderson, Roger Y.",
    title = "Cretaceous-Tertiary palynology, eastern side of the San Juan Basin, New Mexico",
    year = "1960",
    abstract = "Early studies of vertebrate and plant fossils in the San Juan Basin confirmed a late Cretaceous age for the Kirtland Shale and a Tertiary age for the Nacimiento Formation, but resulted in disagreement over the age of the intervening Ojo Alamo Sandstone. Dinosaur evidence indicated a late, but not latest, Cretaceous age, but fragmentary plant megafossils suggested a Tertiary age. Pollen and spore florules collected from within, above, and below the formation tend to confirm a Tertiary age and reflect the environmental changes that accompanied local uplift at the Cretaceous-Tertiary transition. The most significant ecologic change takes place at the base of the Ojo Alamo Sandstone with the appearance of many podocarpaceous and ulmacoues pollen. The most significant change in terms of common forms occurs between the basal Ojo Alamo florule and one collected from a shale unit in the middle of the formation. The basal florule has only four forms in common with the overlying or underlying florules and could be either Cretaceous of Paleocene. The middle florule, however, has nine forms in common with the overlying Nacimiento florules, suggesting Tertiary affinity. Middle Montanan dinosaur bones and fragments, which occur in a similar shale unit on the western side of the basin, may have been reworked or erroneously identified. Proteaceous grains and Tilia are the dominant dicotyledonous types in the Kirtland Shale florule. Conifers are absent. The florule from the base of the Ojo Alamo Sandstone contains more than 70\% Podocarpus pollen, ulmaceous pollen, and several other probable upland types. The middle Ojo Alamo florule contains a mixture of probable upland and lowland forms, as does a florule from the base of the Nacimiento Formation. A florule in the lower part of the Nacimiento Formation is similar to the florule at the base. Ulmaceous pollen, Momipites, and Cupanieidites are the most persistent dicotyledonous types in these three florules. A florule from the uppermost part of the Lewis Shale is a northern equivalent of the Kirtland or lower Ojo Alamo florule but is very different because of a more coastal environment on the opposite shore of the Lewis Sea. The classification system used in this study employs a combination of extant, organ, and form genera arranged in a phylogenetic outline. Eight new genera, Bombacacipites, Brevicolporites, Confertisulcites, Intertriletes, Kurtzipites, Navisulcites, Rectosulcites, and Ulmoideipites, are established, and several others are validated. Of the 88 fossil descriptions, 39 are new species and four are descriptions of dinoflagellates and marine microfossils Incertae Sedis from the Lewis Shale.",
    url = "https://doi.org/10.58799/m-6",
    doi = "10.58799/m-6",
    openalex = "W4323880067"
}

@article{openalexw2246336267,
    author = "Estes, Richard and Berberian, P.A. and Meszoely, Charles A. M.",
    title = "Lower vertebrates from the late Cretaceous Hell Creek Formationc McCone Countyc Montana",
    year = "1969",
    journal = "Breviora",
    openalex = "W2246336267"
}

The family Ornithomimidae is defined on the basis of the skeletal morphology of the three genera Ornithomimus, Struthiomimus, and Dromiceiomimus known in continental strata in Alberta, which are temporally equivalent to the Upper Campanian substage. At least two genera occur in Canadian Lance (Upper Maestrichtian) equivalent strata, but cannot be identified at present. A group of more primitive ornithomimoid theropods is represented else-where by the late Jurassic Elaphrosaurus and early Cretaceous Archaeornithomimus.Ornithomimid attributes include a general body form which parallels that of the ratites; elongate forelimbs, a kinetic skull, enormous eyes, a relatively highly evolved brain, and possibly a secondary palate and supertemporal fenestrae which were nearly encircled by alae of the squamosal. A reconstruction of the myology of the thigh indicates that ornithomimids were extremely fleet, but lacked the agility characteristic of modern large ground birds. They probably subsisted on small, soft-bodied animals.

@article{doi101139e72031,
    author = "Russell, Dale A.",
    title = "Ostrich Dinosaurs from the Late Cretaceous of Western Canada",
    year = "1972",
    journal = "Canadian Journal of Earth Sciences",
    abstract = "The family Ornithomimidae is defined on the basis of the skeletal morphology of the three genera Ornithomimus, Struthiomimus, and Dromiceiomimus known in continental strata in Alberta, which are temporally equivalent to the Upper Campanian substage. At least two genera occur in Canadian Lance (Upper Maestrichtian) equivalent strata, but cannot be identified at present. A group of more primitive ornithomimoid theropods is represented else-where by the late Jurassic Elaphrosaurus and early Cretaceous Archaeornithomimus.Ornithomimid attributes include a general body form which parallels that of the ratites; elongate forelimbs, a kinetic skull, enormous eyes, a relatively highly evolved brain, and possibly a secondary palate and supertemporal fenestrae which were nearly encircled by alae of the squamosal. A reconstruction of the myology of the thigh indicates that ornithomimids were extremely fleet, but lacked the agility characteristic of modern large ground birds. They probably subsisted on small, soft-bodied animals.",
    url = "https://doi.org/10.1139/e72-031",
    doi = "10.1139/e72-031",
    openalex = "W2140641637",
    references = "doi101002jmor1051140102, doi1010160031018271900447, doi105962bhltitle14474, openalexw1879660213, openalexw3208547338"
}

The Hell Creek Formation of eastern Montana, which forms the top of the Cretaceous section, contains in addition to a rich vertebrate fauna a distinctive assemblage of pelecypods, made up of three species of Plesielliptio, one of Rhabdotophorus, two of Plethobasus, one of Quadrula, nine of Proparreysia, one of Obovaria?, one of Corbicula, and one of Sphaerium. Many of the species show distinctive ornamentation, analogous to that of living Unionacea in the Mississippi drainage. One species of Plesielliptio, one of Proparreysia, and one of Sphaerium are new. There is some community of species with the faunas of the Lance and Black Buttes formations of Wyoming, less with the older Cretaceous assemblages, and none with the abundant mollusks of the Paleocene Fort Union formations.

@article{russell1976pelecypods,
    author = "Russell, Loris S.",
    title = "Pelecypods of the Hell Creek Formation (Uppermost Cretaceous) of Garfield County, Montana",
    year = "1976",
    journal = "Canadian Journal of Earth Sciences",
    abstract = "The Hell Creek Formation of eastern Montana, which forms the top of the Cretaceous section, contains in addition to a rich vertebrate fauna a distinctive assemblage of pelecypods, made up of three species of Plesielliptio, one of Rhabdotophorus, two of Plethobasus, one of Quadrula, nine of Proparreysia, one of Obovaria?, one of Corbicula, and one of Sphaerium. Many of the species show distinctive ornamentation, analogous to that of living Unionacea in the Mississippi drainage. One species of Plesielliptio, one of Proparreysia, and one of Sphaerium are new. There is some community of species with the faunas of the Lance and Black Buttes formations of Wyoming, less with the older Cretaceous assemblages, and none with the abundant mollusks of the Paleocene Fort Union formations.",
    url = "https://doi.org/10.1139/e76-039",
    doi = "10.1139/e76-039",
    number = "2",
    openalex = "W2005544138",
    pages = "365-388",
    volume = "13",
    references = "doi105479si00963801221205501, doi105962p234835, openalexw1484819248"
}

The distribution of articulated remains of fossil vertebrates is not uniform within the Oldman Formation (Campanian, Cretaceous) of Dinosaur Provincial Park, Alberta. The mesofauna gradually declines in importance from the west to the east, but a corresponding decline in megafauna does not occur until the eastern limit of the park is reached. The mesofauna is also impoverished low in the exposed section, although the megafauna is as abundant there as in higher levels. Woody vegetation may have supported 88% of the megafaunal herbivore biomass. A fine-grained mosaic of several vegetational types was superimposed on a broader west–east gradient of marsh–forest with an abundant mesofauna to an open woodland dominated by hadrosaurids. High densities of large ectothermic dinosaurs would have made intensive use of available vegetation and profoundly influenced landscapes. Distributions of vertebrates in sedimentary units resulting from normal environmental gradients should be distinguished from those postulated to be associated with the onset of changes that brought the Mesozoic to a close.

@article{doi101139e78109,
    author = "Béland, Pierre and Russell, Dale A.",
    title = "Paleoecology of Dinosaur Provincial Park (Cretaceous), Alberta, interpreted from the distribution of articulated vertebrate remains",
    year = "1978",
    journal = "Canadian Journal of Earth Sciences",
    abstract = "The distribution of articulated remains of fossil vertebrates is not uniform within the Oldman Formation (Campanian, Cretaceous) of Dinosaur Provincial Park, Alberta. The mesofauna gradually declines in importance from the west to the east, but a corresponding decline in megafauna does not occur until the eastern limit of the park is reached. The mesofauna is also impoverished low in the exposed section, although the megafauna is as abundant there as in higher levels. Woody vegetation may have supported 88\% of the megafaunal herbivore biomass. A fine-grained mosaic of several vegetational types was superimposed on a broader west–east gradient of marsh–forest with an abundant mesofauna to an open woodland dominated by hadrosaurids. High densities of large ectothermic dinosaurs would have made intensive use of available vegetation and profoundly influenced landscapes. Distributions of vertebrates in sedimentary units resulting from normal environmental gradients should be distinguished from those postulated to be associated with the onset of changes that brought the Mesozoic to a close.",
    url = "https://doi.org/10.1139/e78-109",
    doi = "10.1139/e78-109",
    openalex = "W1992960775",
    references = "doi101007bf00345312, doi1010160031018271900447, doi101098rstb19710018, doi101111j136520281976tb00242x, doi101126science1874180947, doi1023073608, doi105281zenodo16298542, doi105962bhlpart22969, doi105962bhltitle130546"
}

@article{molnar1980an2,
    author = "Molnar, R. E",
    title = "An albertosaur from the Hell Creek Formation of Montana",
    year = "1980",
    journal = "Journal of Paleontology, v. 54, p. 102-108",
    note = "talkorigins\_source = {true}; raw\_reference = {Molnar, R. E., 1980, An albertosaur from the Hell Creek Formation of Montana: Journal of Paleontology, v. 54, p. 102-108.}"
}

@book{carpenter1982baby1,
    author = "Carpenter, K",
    title = "Baby dinosaurs from the Late Cretaceous Lance and Hell Creek Formations, and a description of a new species of theropod",
    year = "1982",
    publisher = "University of Wyoming Contributions to Geology, v. 20, p. 123-134",
    note = "talkorigins\_source = {true}; raw\_reference = {Carpenter, K., 1982, Baby dinosaurs from the Late Cretaceous Lance and Hell Creek Formations, and a description of a new species of theropod: University of Wyoming Contributions to Geology, v. 20, p. 123-134.}"
}

@article{doi10113000917613198210153ucbamh20co2,
    author = "Archibald, J. David and Butler, Robert F. and Lindsay, Everett H. and Clemens, William A. and Dingus, Lowell",
    title = "Upper Cretaceous–Paleocene biostratigraphy and magnetostratigraphy, Hell Creek and Tullock Formations, northeastern Montana",
    year = "1982",
    journal = "Geology",
    url = "https://doi.org/10.1130/0091-7613(1982)10<153:ucbamh>2.0.co;2",
    doi = "10.1130/0091-7613(1982)10<153:ucbamh>2.0.co;2",
    openalex = "W2013405608"
}

Inaccurate stratigraphic correlations in the Hell Creek area, Montana, have led to the assumption that transitional vertebrate faunas (Bug Creek Anthills) exist in the latest Cretaceous, refuting a catastrophic turnover at the Cretaceous-Tertiary boundary. Establishment of the transitional faunas in Paleocene channels that cut down through the Cretaceous-Tertiary boundary renders the terrestrial faunal record compatible with the marine record and with catastrophic extinction.

@article{doi101126science22346411177,
    author = "Smit, Jan and van der Kaars, Sander",
    title = "Terminal Cretaceous Extinctions in the Hell Creek Area, Montana: Compatible with Catastrophic Extinction",
    year = "1984",
    journal = "Science",
    abstract = "Inaccurate stratigraphic correlations in the Hell Creek area, Montana, have led to the assumption that transitional vertebrate faunas (Bug Creek Anthills) exist in the latest Cretaceous, refuting a catastrophic turnover at the Cretaceous-Tertiary boundary. Establishment of the transitional faunas in Paleocene channels that cut down through the Cretaceous-Tertiary boundary renders the terrestrial faunal record compatible with the marine record and with catastrophic extinction.",
    url = "https://doi.org/10.1126/science.223.4641.1177",
    doi = "10.1126/science.223.4641.1177",
    openalex = "W1973856653",
    references = "alvarez1980extraterrestrial, doi1010160016703782903829, doi1010160195667182900313, doi101038288651a0, doi101073pnas802627, doi101126science2094459921, doi101126science2194584495, doi101126science21945911383, doi10113000917613198210153ucbamh20co2, doi101130spe190p329"
}

Dinosaur extinction in Montana, Alberta, and Wyoming was a gradual process that began 7 million years before the end of the Cretaceous and accelerated rapidly in the final 0.3 million years of the Cretaceous, during the interval of apparent competition from rapidly evolving immigrating ungulates. This interval involves rapid reduction in both diversity and population density of dinosaurs. The last dinosaurs known are from a channel that contains teeth of Mantuan mammals, seven species of dinosaurs, and Paleocene pollen. The top of this channel is 1.3 meters above the likely position of the iridium anomaly, the Cretaceous/Tertiary boundary.

@article{sloan1986gradual,
    author = "Sloan, Robert E. and Rigby, J. Keith and Van Valen, Leigh M. and Gabriel, Diane",
    title = "Gradual Dinosaur Extinction and Simultaneous Ungulate Radiation in the Hell Creek Formation",
    year = "1986",
    journal = "Science",
    abstract = "Dinosaur extinction in Montana, Alberta, and Wyoming was a gradual process that began 7 million years before the end of the Cretaceous and accelerated rapidly in the final 0.3 million years of the Cretaceous, during the interval of apparent competition from rapidly evolving immigrating ungulates. This interval involves rapid reduction in both diversity and population density of dinosaurs. The last dinosaurs known are from a channel that contains teeth of Mantuan mammals, seven species of dinosaurs, and Paleocene pollen. The top of this channel is 1.3 meters above the likely position of the iridium anomaly, the Cretaceous/Tertiary boundary.",
    url = "https://doi.org/10.1126/science.232.4750.629",
    doi = "10.1126/science.232.4750.629",
    number = "4750",
    pages = "629-633",
    volume = "232"
}

@misc{sloan1986gradual3,
    author = "Sloan, R. E. et al",
    title = "Gradual dinosaur extinction and simultaneous ungulate radiation in the Hell Creek Formation",
    year = "1986",
    howpublished = "Science, v. 232, p. 629-633",
    note = "talkorigins\_source = {true}; raw\_reference = {Sloan, R. E. et al., 1986, Gradual dinosaur extinction and simultaneous ungulate radiation in the Hell Creek Formation: Science, v. 232, p. 629-633.}"
}

@article{rigby1987dinosaurs,
    author = "Rigby, J. Keith and Newman, Karl R. and Kaars, Jan Smit Sander Van Der and Sloan, Robert E. and Rigby, J. Keith",
    title = "Dinosaurs from the Paleocene Part of the Hell Creek Formation, McCone County, Montana",
    year = "1987",
    journal = "PALAIOS",
    url = "https://doi.org/10.2307/3514679",
    doi = "10.2307/3514679",
    number = "3",
    openalex = "W2315183814",
    pages = "296",
    volume = "2",
    references = "alvarez1980extraterrestrial, doi101126science21445271341, doi101126science22346411135, doi101126science22346411177, doi101126science2314739714, doi10113000917613198210153ucbamh20co2, doi10113000917613198614279ssaedt20co2"
}

ABSTRACT Melvius thomasi, new genus and new species, from the Late Cretaceous Hell Creek Formation of northeastern Montana and Wyoming, is one of the largest known amiids (standard length 160 cm or more). It is based on disarticulated elements of the skull and axial skeleton. Additional isolated elements probably referable to this species are known from North and South Dakota, Utah, Texas and New Mexico. All known specimens occur below the Cretaceous-Tertiary boundary. Specimens of large amiids from the Early Cretaceous Trinity Formation, Texas, may also be referable to this or a related taxon. Detailed comparison with other amiids, described from more complete material, is not yet possible, but some features of the new taxon appear to relate it to Enneles and Pachyamia. Melvius lived in estuaries and large rivers along the western margin of the Western Interior Sea.

@article{doi10108002724634198810011669,
    author = "Bryant, Laurie J.",
    title = "A new genus and species of Amiidae (Holostei; Osteichthyes) from the Late Cretaceous of North America, with comments on the phylogeny of the Amiidae",
    year = "1988",
    journal = "Journal of Vertebrate Paleontology",
    abstract = "ABSTRACT Melvius thomasi, new genus and new species, from the Late Cretaceous Hell Creek Formation of northeastern Montana and Wyoming, is one of the largest known amiids (standard length 160 cm or more). It is based on disarticulated elements of the skull and axial skeleton. Additional isolated elements probably referable to this species are known from North and South Dakota, Utah, Texas and New Mexico. All known specimens occur below the Cretaceous-Tertiary boundary. Specimens of large amiids from the Early Cretaceous Trinity Formation, Texas, may also be referable to this or a related taxon. Detailed comparison with other amiids, described from more complete material, is not yet possible, but some features of the new taxon appear to relate it to Enneles and Pachyamia. Melvius lived in estuaries and large rivers along the western margin of the Western Interior Sea.",
    url = "https://doi.org/10.1080/02724634.1988.10011669",
    doi = "10.1080/02724634.1988.10011669",
    openalex = "W1986397142",
    references = "doi10113000917613198614279ssaedt20co2"
}

@article{lofgren1990reworking,
    author = "Lofgren, Donald L. and Hotton, Carol L. and Runkel, Anthony C.",
    title = "Reworking of Cretaceous dinosaurs into Paleocene channel, deposits, upper Hell Creek Formation, Montana",
    year = "1990",
    journal = "Geology",
    url = "https://doi.org/10.1130/0091-7613(1990)018<0874:rocdip>2.3.co;2",
    doi = "10.1130/0091-7613(1990)018<0874:rocdip>2.3.co;2",
    number = "9",
    openalex = "W2059769021",
    pages = "874",
    volume = "18"
}

Results of a three-year field study of family-level patterns of ecological diversity of dinosaurs in the Hell Creek Formation of Montana and North Dakota show no evidence (probability P < 0.05) of a gradual decline of dinosaurs at the end of the Cretaceous. Stratigraphic reliability was maintained through a tripartite division of the Hell Creek, and preservational biases were corrected for by comparison of results only from similar fades as well as through the use of large-scale, statistically rigorous survey and collection procedures. The findings are in agreement with an abrupt extinction event such as one caused by an asteroid impact.

@article{doi101126science11536489,
    author = "Sheehan, Peter M. and Fastovsky, David E. and Hoffmann, Raymond G. and Berghaus, Claudia B. and Gabriel, Diane L.",
    title = "Sudden Extinction of the Dinosaurs: Latest Cretaceous, Upper Great Plains, USA",
    year = "1991",
    journal = "Science",
    abstract = "Results of a three-year field study of family-level patterns of ecological diversity of dinosaurs in the Hell Creek Formation of Montana and North Dakota show no evidence (probability P < 0.05) of a gradual decline of dinosaurs at the end of the Cretaceous. Stratigraphic reliability was maintained through a tripartite division of the Hell Creek, and preservational biases were corrected for by comparison of results only from similar fades as well as through the use of large-scale, statistically rigorous survey and collection procedures. The findings are in agreement with an abrupt extinction event such as one caused by an asteroid impact.",
    url = "https://doi.org/10.1126/science.11536489",
    doi = "10.1126/science.11536489",
    openalex = "W2101062605",
    references = "doi101038307360a0, doi10113000917613198614279ssaedt20co2"
}

Late Cretaceous (Cenomanian) fossils discovered in the Kem Kem region of Morocco include large predatory dinosaurs that inhabited Africa as it drifted into geographic isolation. One, represented by a skull approximately 1.6 meters in length, is an advanced allosauroid referable to the African genus Carcharodontosaurus. Another, represented by a partial skeleton with slender proportions, is a new basal coelurosaur closely resembling the Egyptian genus Bahariasaurus. Comparisons with Cretaceous theropods from other continents reveal a previously unrecognized global radiation of carcharodontosaurid predators. Substantial geographic differentiation of dinosaurian faunas in response to continental drift appears to have arisen abruptly at the beginning of the Late Cretaceous.

@article{doi101126science2725264986,
    author = "Sereno, Paul C. and Dutheil, Didier B. and Iarochène, Mohamed and Larsson, Hans C. E. and Lyon, Gabrielle H. and Magwene, Paul M. and Sidor, Christian A. and Varricchio, David J. and Wilson, Jeffrey A.",
    title = "Predatory Dinosaurs from the Sahara and Late Cretaceous Faunal Differentiation",
    year = "1996",
    journal = "Science",
    abstract = "Late Cretaceous (Cenomanian) fossils discovered in the Kem Kem region of Morocco include large predatory dinosaurs that inhabited Africa as it drifted into geographic isolation. One, represented by a skull approximately 1.6 meters in length, is an advanced allosauroid referable to the African genus Carcharodontosaurus. Another, represented by a partial skeleton with slender proportions, is a new basal coelurosaur closely resembling the Egyptian genus Bahariasaurus. Comparisons with Cretaceous theropods from other continents reveal a previously unrecognized global radiation of carcharodontosaurid predators. Substantial geographic differentiation of dinosaurian faunas in response to continental drift appears to have arisen abruptly at the beginning of the Late Cretaceous.",
    url = "https://doi.org/10.1126/science.272.5264.986",
    doi = "10.1126/science.272.5264.986",
    openalex = "W2013182835",
    references = "coria1995a, doi101007bf02987808, doi101016s0016699509900389, doi101038377224a0, doi101126science2665183267, doi102113gssgfbulliv2335, doi1023072421859, doi105281zenodo1040385, doi105962p226819, openalexw1426920053, openalexw2603028126"
}

Late Cretaceous trace fossils from the Two Medicine Formation of Montana are interpreted as herbivorous dinosaur feces reworked by scarabaeine dung beetles. These irregular blocks of comminuted plant material occur in isolated patches in fluvial flood plain sediments near dinosaur bone beds and nesting grounds. Numerous burrows in and around the specimens indicate significant invertebrate activity which suggests intense competition for a rich food resource. Some of the burrows are backfilled with organic matter that had been translocated from the organic mass (dung pat) into the adjacent sediment. Paracoprid dung beetles are the only extant organisms known to make similar caches. These unique ichnofossils provide evidence for commensal interactions between dung beetles, herbivorous dinosaurs, and conifers. This find also reveals a pathway through which fecal resources were recycled and suggests that scarabs evolved coprophagy through association with dinosaurs.

@article{doi1023073515235,
    author = "Chin, Karen and Gill, Bruce D.",
    title = "Dinosaurs, Dung Beetles, and Conifers: Participants in a Cretaceous Food Web",
    year = "1996",
    journal = "Palaios",
    abstract = "Late Cretaceous trace fossils from the Two Medicine Formation of Montana are interpreted as herbivorous dinosaur feces reworked by scarabaeine dung beetles. These irregular blocks of comminuted plant material occur in isolated patches in fluvial flood plain sediments near dinosaur bone beds and nesting grounds. Numerous burrows in and around the specimens indicate significant invertebrate activity which suggests intense competition for a rich food resource. Some of the burrows are backfilled with organic matter that had been translocated from the organic mass (dung pat) into the adjacent sediment. Paracoprid dung beetles are the only extant organisms known to make similar caches. These unique ichnofossils provide evidence for commensal interactions between dung beetles, herbivorous dinosaurs, and conifers. This find also reveals a pathway through which fecal resources were recycled and suggests that scarabs evolved coprophagy through association with dinosaurs.",
    url = "https://doi.org/10.2307/3515235",
    doi = "10.2307/3515235",
    openalex = "W1966939491",
    references = "doi101038282296a0, doi101139e78109"
}

@incollection{russell2002synopsis,
    author = "Russell, Dale A. and Manabe, Makoto",
    title = "Synopsis of the Hell Creek (uppermost Cretaceous) dinosaur assemblage",
    year = "2002",
    booktitle = "The Hell Creek Formation and the Cretaceous-Tertiary boundary in the northern Great Plains: An Integrated continental record of the end of the Cretaceous",
    url = "https://doi.org/10.1130/0-8137-2361-2.169",
    doi = "10.1130/0-8137-2361-2.169"
}

Currie, Philip J. (2003): Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada. Palaeontologica Polonica 48 (2): 191-226, DOI: 10.5281/zenodo.3725717, URL: https://www.app.pan.pl/archive/published/app48/app48-191.pdf

@article{doi105281zenodo3725717,
    author = "Currie, Philip J.",
    title = "Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada",
    year = "2003",
    journal = "reroDoc Digital Library",
    abstract = "Currie, Philip J. (2003): Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada. Palaeontologica Polonica 48 (2): 191-226, DOI: 10.5281/zenodo.3725717, URL: https://www.app.pan.pl/archive/published/app48/app48-191.pdf",
    url = "https://doi.org/10.5281/zenodo.3725717",
    doi = "10.5281/zenodo.3725717",
    openalex = "W2107092189",
    references = "carr1999craniofacial, crossref1976allosaurus, currie1985cranial, doi101017cbo9780511608377011, doi101038358059a0, doi10108002724634199510011574, doi10108002724634199710011027, doi10108002724634199910011161, doi101139e02083, doi1015468lnfamn, doi1015468yhxmzl, doi1023071292217, doi1023073514548, doi1034191b109, doi104095101672, doi105281zenodo1037529, doi105281zenodo1040973, doi105281zenodo1048848, doi105281zenodo814935, vonhuene1923carnivorous"
}

The Nanxiong and Shanghu Formations of southeastern China span the KT boundary interval and preserve an important paleontological record. A 1285‐m section across the KT boundary was measured, and lithological units were documented and sampled. Strata were deposited in alluvial fan/playa mudflat environments in a highly seasonal, semiarid climate. Previous workers placed the KT boundary at the Nanxiong/Shanghu formational contact. The uppermost Nanxiong and lowermost Shanghu Formations contain an assemblage of dinosaur egg fragments and Tertiary fossils, which led to the notion that dinosaurs survived into the Paleocene. On the basis of our results, we argue that the mixed KT assemblage is a result of debris flows reworking Cretaceous fossils. Depositional environments and paleoclimate did not change significantly across the KT boundary.

@article{doi101086379695,
    author = "Buck, Brenda J. and Hanson, Andrew D. and Hengst, Richard A. and Hu, Shusheng",
    title = "“Tertiary Dinosaurs” in the Nanxiong Basin, Southern China, Are Reworked from the Cretaceous",
    year = "2004",
    journal = "The Journal of Geology",
    abstract = "The Nanxiong and Shanghu Formations of southeastern China span the KT boundary interval and preserve an important paleontological record. A 1285‐m section across the KT boundary was measured, and lithological units were documented and sampled. Strata were deposited in alluvial fan/playa mudflat environments in a highly seasonal, semiarid climate. Previous workers placed the KT boundary at the Nanxiong/Shanghu formational contact. The uppermost Nanxiong and lowermost Shanghu Formations contain an assemblage of dinosaur egg fragments and Tertiary fossils, which led to the notion that dinosaurs survived into the Paleocene. On the basis of our results, we argue that the mixed KT assemblage is a result of debris flows reworking Cretaceous fossils. Depositional environments and paleoclimate did not change significantly across the KT boundary.",
    url = "https://doi.org/10.1086/379695",
    doi = "10.1086/379695",
    openalex = "W1991908329",
    references = "alvarez1980extraterrestrial, doi101016s0012821x00002387, doi101038359819a0, doi101086629677, doi1010970001069419660500000001, doi101111j136530911989tb00608x, doi1011300016760619931050129cop23co2, doi1011300091761319910190867ccapct23co2, doi101130spe203p1, lofgren1990reworking, sloan1986gradual"
}

Contributors Preface Acknowledgments I. Beaked Dinosaurs: The Ornithopods 1. Callovosaurus leedsi, the Earliest Dryosaurid Dinosaur (Ornithischia: Euornithopoda) from the Middle Jurassic of England Jose Ignacio Ruiz-Omenaca, Xabier Pereda Suberbiola, and Peter M. Galton 2. Teeth of Ornithischian Dinosaurs (Mostly Ornithopoda) from the Morrison Formation (Upper Jurassic) of the Western United States Peter M. Galton 3. A Description of a New Ornithopod from the Lytle Member of the Purgatoire Formation (Lower Cretaceous) and a Reassessment of the Skull of Camptosaurus Kathleen Brill and Kenneth Carpenter 4. Turning the Old into the New: A Separate Genus for the Gracile Iguanodont from the Wealden of England Gregory S. Paul 5. A Possible New Basal Hadrosaur from the Lower Cretaceous Cedar Mountain Formation of Eastern Utah David Gilpin, Tony DiCroce, and Kenneth Carpenter 6. Postcranial Osteology of the Hadrosaurid Dinosaur Brachylophosaurus canadensis from the Late Cretaceous of Montana Albert Prieto-Marquez 7. Leonardo, a Mummified Brachylophosaurus (Ornithischia: Hadrosauridae) from the Judith River Formation of Montana Nate L. Murphy, David Trexler, and Mark Thompson 8. Discussion of Character Analysis of the Appendicular Anatomy in Campanian and Maastrichtian North American Hadrosaurids-Variation and Ontogeny Michael K. Brett-Surman and Jonathan R. Wagner 9. Osteochondrosis in Late Cretaceous Hadrosauria: A Manifestation of Ontologic Failure Bruce Rothschild and Darren H. Tanke 10. Deciphering Duckbills: A History in Nomenclature Benjamin S. Creisler II. Horned Dinosaurs: Ceratopsians 11. Cranial Anatomy and Biogeography of the First Leptoceratops gracilis (Dinosauria: Ornithischia) Specimens from the Hell Creek Formation, Southeast Montana Christopher J. Ott 12. Cranial Osteology and Phylogenetic Relationships of the Chasmosaurine Ceratopsid Torosaurus latus Andrew A. Farke 13. Growth and Population Age Structure in the Horned Dinosaur Chasmosaurus Thomas M. Lehman 14. Bone Resorption, Bone Lesions, and Extracranial Fenestrae in Ceratopsid Dinosaurs: A Preliminary Assessment Darren H. Tanke and Andrew A. Farke 15. Bison alticornis and O. C. Marsh's Early Views on Ceratopsians Kenneth Carpenter Index

@book{openalexw597685939,
    author = "Carpenter, Kenneth",
    title = "Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs",
    year = "2006",
    booktitle = "Project Muse (Johns Hopkins University)",
    abstract = "Contributors Preface Acknowledgments I. Beaked Dinosaurs: The Ornithopods 1. Callovosaurus leedsi, the Earliest Dryosaurid Dinosaur (Ornithischia: Euornithopoda) from the Middle Jurassic of England Jose Ignacio Ruiz-Omenaca, Xabier Pereda Suberbiola, and Peter M. Galton 2. Teeth of Ornithischian Dinosaurs (Mostly Ornithopoda) from the Morrison Formation (Upper Jurassic) of the Western United States Peter M. Galton 3. A Description of a New Ornithopod from the Lytle Member of the Purgatoire Formation (Lower Cretaceous) and a Reassessment of the Skull of Camptosaurus Kathleen Brill and Kenneth Carpenter 4. Turning the Old into the New: A Separate Genus for the Gracile Iguanodont from the Wealden of England Gregory S. Paul 5. A Possible New Basal Hadrosaur from the Lower Cretaceous Cedar Mountain Formation of Eastern Utah David Gilpin, Tony DiCroce, and Kenneth Carpenter 6. Postcranial Osteology of the Hadrosaurid Dinosaur Brachylophosaurus canadensis from the Late Cretaceous of Montana Albert Prieto-Marquez 7. Leonardo, a Mummified Brachylophosaurus (Ornithischia: Hadrosauridae) from the Judith River Formation of Montana Nate L. Murphy, David Trexler, and Mark Thompson 8. Discussion of Character Analysis of the Appendicular Anatomy in Campanian and Maastrichtian North American Hadrosaurids-Variation and Ontogeny Michael K. Brett-Surman and Jonathan R. Wagner 9. Osteochondrosis in Late Cretaceous Hadrosauria: A Manifestation of Ontologic Failure Bruce Rothschild and Darren H. Tanke 10. Deciphering Duckbills: A History in Nomenclature Benjamin S. Creisler II. Horned Dinosaurs: Ceratopsians 11. Cranial Anatomy and Biogeography of the First Leptoceratops gracilis (Dinosauria: Ornithischia) Specimens from the Hell Creek Formation, Southeast Montana Christopher J. Ott 12. Cranial Osteology and Phylogenetic Relationships of the Chasmosaurine Ceratopsid Torosaurus latus Andrew A. Farke 13. Growth and Population Age Structure in the Horned Dinosaur Chasmosaurus Thomas M. Lehman 14. Bone Resorption, Bone Lesions, and Extracranial Fenestrae in Ceratopsid Dinosaurs: A Preliminary Assessment Darren H. Tanke and Andrew A. Farke 15. Bison alticornis and O. C. Marsh's Early Views on Ceratopsians Kenneth Carpenter Index",
    openalex = "W597685939"
}

Fossils of the Early Cretaceous dinosaur, Nigersaurus taqueti, document for the first time the cranial anatomy of a rebbachisaurid sauropod. Its extreme adaptations for herbivory at ground-level challenge current hypotheses regarding feeding function and feeding strategy among diplodocoids, the larger clade of sauropods that includes Nigersaurus. We used high resolution computed tomography, stereolithography, and standard molding and casting techniques to reassemble the extremely fragile skull. Computed tomography also allowed us to render the first endocast for a sauropod preserving portions of the olfactory bulbs, cerebrum and inner ear, the latter permitting us to establish habitual head posture. To elucidate evidence of tooth wear and tooth replacement rate, we used photographic-casting techniques and crown thin sections, respectively. To reconstruct its 9-meter postcranial skeleton, we combined and size-adjusted multiple partial skeletons. Finally, we used maximum parsimony algorithms on character data to obtain the best estimate of phylogenetic relationships among diplodocoid sauropods. Nigersaurus taqueti shows extreme adaptations for a dinosaurian herbivore including a skull of extremely light construction, tooth batteries located at the distal end of the jaws, tooth replacement as fast as one per month, an expanded muzzle that faces directly toward the ground, and hollow presacral vertebral centra with more air sac space than bone by volume. A cranial endocast provides the first reasonably complete view of a sauropod brain including its small olfactory bulbs and cerebrum. Skeletal and dental evidence suggests that Nigersaurus was a ground-level herbivore that gathered and sliced relatively soft vegetation, the culmination of a low-browsing feeding strategy first established among diplodocoids during the Jurassic.

@article{doi101371journalpone0001230,
    author = "Sereno, Paul C. and Wilson, Jeffrey A. and Witmer, Lawrence M. and Whitlock, John A. and Maga, Abdoulaye and Idé, Oumarou and Rowe, Timothy A.",
    title = "Structural Extremes in a Cretaceous Dinosaur",
    year = "2007",
    journal = "PLoS ONE",
    abstract = "Fossils of the Early Cretaceous dinosaur, Nigersaurus taqueti, document for the first time the cranial anatomy of a rebbachisaurid sauropod. Its extreme adaptations for herbivory at ground-level challenge current hypotheses regarding feeding function and feeding strategy among diplodocoids, the larger clade of sauropods that includes Nigersaurus. We used high resolution computed tomography, stereolithography, and standard molding and casting techniques to reassemble the extremely fragile skull. Computed tomography also allowed us to render the first endocast for a sauropod preserving portions of the olfactory bulbs, cerebrum and inner ear, the latter permitting us to establish habitual head posture. To elucidate evidence of tooth wear and tooth replacement rate, we used photographic-casting techniques and crown thin sections, respectively. To reconstruct its 9-meter postcranial skeleton, we combined and size-adjusted multiple partial skeletons. Finally, we used maximum parsimony algorithms on character data to obtain the best estimate of phylogenetic relationships among diplodocoid sauropods. Nigersaurus taqueti shows extreme adaptations for a dinosaurian herbivore including a skull of extremely light construction, tooth batteries located at the distal end of the jaws, tooth replacement as fast as one per month, an expanded muzzle that faces directly toward the ground, and hollow presacral vertebral centra with more air sac space than bone by volume. A cranial endocast provides the first reasonably complete view of a sauropod brain including its small olfactory bulbs and cerebrum. Skeletal and dental evidence suggests that Nigersaurus was a ground-level herbivore that gathered and sliced relatively soft vegetation, the culmination of a low-browsing feeding strategy first established among diplodocoids during the Jurassic.",
    url = "https://doi.org/10.1371/journal.pone.0001230",
    doi = "10.1371/journal.pone.0001230",
    openalex = "W2111030938",
    references = "doi10100797844317693306, doi101017cbo9780511536045, doi101017s0094837300007557, doi101038274661a0, doi101038nature02048, doi101046j10963642200200029x, doi101073pnas932514623, doi10108002724634199810011115, doi101126science1118806, doi101525california97805202462320010001, doi105860choice260307, doi105962bhltitle102117, doi105962bhltitle60562, doi105962p234818, larsson2000forebrain, openalexw2983381470, openalexw2989049194"
}

ABSTRACT The first detailed description of the lambeosaurine Lambeosaurus magnicristatus (Ornithischia: Hadrosauridae) confirms that it is a distinct taxon characterized by its comparatively enormous cranial crest, formed predominantly by the caudodorsal process of the premaxilla, and an acute crest-snout angle. The holotype of L. magnicristatus occurs stratigraphically higher than all other Dinosaur Park Formation lambeosaurines at the Dinosaur Provincial Park locality. The only referred specimen was collected over 170 kilometers southeast of the type locality. Correlation of its host stratum with the well-known Dinosaur Park section reveals that L. magnicristatus has no biostratigraphic overlap with L. lambei and suggests that it replaces L. lambei on a regional scale in southern Alberta at the end of ‘Dinosaur Park time.’ Species-level phylogenetic analysis of Lambeosaurinae corroborates the monophyly of Lambeosaurus. The genus is characterized by five apomorphies, including a procumbent crest, complete enclosure of the ophthalmic canal of the laterosphenoid, the presence of a flange on the caudodorsal process of the premaxilla that overlaps the nasal in the rostral region of the crest, caudal extension of the premaxilla such that it forms the caudal margin of the crest, and a unique joint between the rostral nasal and the caudodorsal process of the premaxilla. Lambeosaurine phylogeny indicates that the development of a hypertrophied cranial crest evolved independently at least three times within the clade, suggesting that the crest enlargement is a recurring evolutionary trend within Lambeosaurinae.

@article{doi10167102724634200727373aarolm20co2,
    author = "Evans, David C. and Reisz, Robert R.",
    title = "Anatomy and Relationships of Lambeosaurus magnicristatus, a crested hadrosaurid dinosaur (Ornithischia) from the Dinosaur Park Formation, Alberta",
    year = "2007",
    journal = "Journal of Vertebrate Paleontology",
    abstract = "ABSTRACT The first detailed description of the lambeosaurine Lambeosaurus magnicristatus (Ornithischia: Hadrosauridae) confirms that it is a distinct taxon characterized by its comparatively enormous cranial crest, formed predominantly by the caudodorsal process of the premaxilla, and an acute crest-snout angle. The holotype of L. magnicristatus occurs stratigraphically higher than all other Dinosaur Park Formation lambeosaurines at the Dinosaur Provincial Park locality. The only referred specimen was collected over 170 kilometers southeast of the type locality. Correlation of its host stratum with the well-known Dinosaur Park section reveals that L. magnicristatus has no biostratigraphic overlap with L. lambei and suggests that it replaces L. lambei on a regional scale in southern Alberta at the end of ‘Dinosaur Park time.’ Species-level phylogenetic analysis of Lambeosaurinae corroborates the monophyly of Lambeosaurus. The genus is characterized by five apomorphies, including a procumbent crest, complete enclosure of the ophthalmic canal of the laterosphenoid, the presence of a flange on the caudodorsal process of the premaxilla that overlaps the nasal in the rostral region of the crest, caudal extension of the premaxilla such that it forms the caudal margin of the crest, and a unique joint between the rostral nasal and the caudodorsal process of the premaxilla. Lambeosaurine phylogeny indicates that the development of a hypertrophied cranial crest evolved independently at least three times within the clade, suggesting that the crest enlargement is a recurring evolutionary trend within Lambeosaurinae.",
    url = "https://doi.org/10.1671/0272-4634(2007)27[373:aarolm]2.0.co;2",
    doi = "10.1671/0272-4634(2007)27[373:aarolm]2.0.co;2",
    openalex = "W2179137073",
    references = "doi101017s0025315400028575, doi101038122881a0, doi10108002724634199510011271, doi101111j1474919x1955tb01923x, doi101126science11282807, doi101139e78109, doi1016430045851120000000907br20co2, doi1023071005355, doi102475ajss32313381, doi105860choice435902, gilmore1924a, openalexw3215057009"
}

A quantitative study based on unionoid bivalve presence-absence data, species abundance, shell morphology, and sedimentological data provides a more detailed paleoecological interpretation of the Upper Cretaceous Hell Creek Formation. The Proparreysia and the Pleurobema faunal assemblages can be separated on the basis of taxonomic diversity and species composition. While the first consists of 19 species, including trigonal and elongate shell morphologies, the latter consists of only 3 species characterized by elongate shells. A riverine environment is interpreted for most species from the quantitative analysis of shell morphology. Only one species (cf. Pleiodon sp.) is from a lacustrine habitat. The main river channels of the Hell Creek paleodrainage system are the habitat of bivalves of the Proparreysia assemblage through a combined interpretation of the morphology and diversity data. In contrast, the bivalves of the Pleurobema assemblage are from secondary channels and tributaries of the main river channels. The mode of deposition of the two assemblages is very similar, as they are preserved predominantly in crevasse-splay deposits. The long-term ecosystem stability, high habitat heterogeneity, and a variable degree in floodplain connectivity of the habitats in the midreach of the Hell Creek paleodrainage system resulted in the high taxonomic diversity of the unionoid bivalves and the separation of the unionoid faunal assemblages.

@article{doi102110palo2005p05059r,
    author = "Scholz, Hans and Hartman, Joseph H.",
    title = "PALEOENVIRONMENTAL RECONSTRUCTION OF THE UPPER CRETACEOUS HELL CREEK FORMATION OF THE WILLISTON BASIN, MONTANA, USA: IMPLICATIONS FROM THE QUANTITATIVE ANALYSIS OF UNIONOID BIVALVE TAXONOMIC DIVERSITY AND MORPHOLOGIC DISPARITY",
    year = "2007",
    journal = "Palaios",
    abstract = "A quantitative study based on unionoid bivalve presence-absence data, species abundance, shell morphology, and sedimentological data provides a more detailed paleoecological interpretation of the Upper Cretaceous Hell Creek Formation. The Proparreysia and the Pleurobema faunal assemblages can be separated on the basis of taxonomic diversity and species composition. While the first consists of 19 species, including trigonal and elongate shell morphologies, the latter consists of only 3 species characterized by elongate shells. A riverine environment is interpreted for most species from the quantitative analysis of shell morphology. Only one species (cf. Pleiodon sp.) is from a lacustrine habitat. The main river channels of the Hell Creek paleodrainage system are the habitat of bivalves of the Proparreysia assemblage through a combined interpretation of the morphology and diversity data. In contrast, the bivalves of the Pleurobema assemblage are from secondary channels and tributaries of the main river channels. The mode of deposition of the two assemblages is very similar, as they are preserved predominantly in crevasse-splay deposits. The long-term ecosystem stability, high habitat heterogeneity, and a variable degree in floodplain connectivity of the habitats in the midreach of the Hell Creek paleodrainage system resulted in the high taxonomic diversity of the unionoid bivalves and the separation of the unionoid faunal assemblages.",
    url = "https://doi.org/10.2110/palo.2005.p05-059r",
    doi = "10.2110/palo.2005.p05-059r",
    openalex = "W2167317494",
    references = "russell1976pelecypods"
}

@article{crossref2008the,
    title = "The evolutionists: American thinkers confront Charles Darwin, 1860-1920",
    year = "2008",
    journal = "Choice Reviews Online",
    url = "https://doi.org/10.5860/choice.45-2797",
    doi = "10.5860/choice.45-2797",
    number = "05",
    pages = "45-2797-45-2797",
    volume = "45"
}

The observed diversity of dinosaurs reached its highest peak during the mid- and Late Cretaceous, the 50 Myr that preceded their extinction, and yet this explosion of dinosaur diversity may be explained largely by sampling bias. It has long been debated whether dinosaurs were part of the Cretaceous Terrestrial Revolution (KTR), from 125-80 Myr ago, when flowering plants, herbivorous and social insects, squamates, birds and mammals all underwent a rapid expansion. Although an apparent explosion of dinosaur diversity occurred in the mid-Cretaceous, coinciding with the emergence of new groups (e.g. neoceratopsians, ankylosaurid ankylosaurs, hadrosaurids and pachycephalosaurs), results from the first quantitative study of diversification applied to a new supertree of dinosaurs show that this apparent burst in dinosaurian diversity in the last 18 Myr of the Cretaceous is a sampling artefact. Indeed, major diversification shifts occurred largely in the first one-third of the group's history. Despite the appearance of new clades of medium to large herbivores and carnivores later in dinosaur history, these new originations do not correspond to significant diversification shifts. Instead, the overall geometry of the Cretaceous part of the dinosaur tree does not depart from the null hypothesis of an equal rates model of lineage branching. Furthermore, we conclude that dinosaurs did not experience a progressive decline at the end of the Cretaceous, nor was their evolution driven directly by the KTR.

@article{doi101098rspb20080715,
    author = "Lloyd, Graeme T. and Davis, Katie E. and Pisani, Davide and Tarver, James E. and Ruta, Marcello and Sakamoto, Manabu and Hone, David W. E. and Jennings, Rachel and Benton, Michael J.",
    title = "Dinosaurs and the Cretaceous Terrestrial Revolution",
    year = "2008",
    journal = "Proceedings of the Royal Society B Biological Sciences",
    abstract = "The observed diversity of dinosaurs reached its highest peak during the mid- and Late Cretaceous, the 50 Myr that preceded their extinction, and yet this explosion of dinosaur diversity may be explained largely by sampling bias. It has long been debated whether dinosaurs were part of the Cretaceous Terrestrial Revolution (KTR), from 125-80 Myr ago, when flowering plants, herbivorous and social insects, squamates, birds and mammals all underwent a rapid expansion. Although an apparent explosion of dinosaur diversity occurred in the mid-Cretaceous, coinciding with the emergence of new groups (e.g. neoceratopsians, ankylosaurid ankylosaurs, hadrosaurids and pachycephalosaurs), results from the first quantitative study of diversification applied to a new supertree of dinosaurs show that this apparent burst in dinosaurian diversity in the last 18 Myr of the Cretaceous is a sampling artefact. Indeed, major diversification shifts occurred largely in the first one-third of the group's history. Despite the appearance of new clades of medium to large herbivores and carnivores later in dinosaur history, these new originations do not correspond to significant diversification shifts. Instead, the overall geometry of the Cretaceous part of the dinosaur tree does not depart from the null hypothesis of an equal rates model of lineage branching. Furthermore, we conclude that dinosaurs did not experience a progressive decline at the end of the Cretaceous, nor was their evolution driven directly by the KTR.",
    url = "https://doi.org/10.1098/rspb.2008.0715",
    doi = "10.1098/rspb.2008.0715",
    openalex = "W2131872692",
    references = "doi101007978140206754912413, doi101017cbo9780511536045, doi101038274661a0, doi101038nature05634, doi101046j14610248200100230x, doi101073pnas0606028103, doi101073pnas111144698, doi101093bioinformatics124357, doi101111j109600311999tb00277x, doi101126science1118806, doi101126science1144066, doi101159000452856, doi1015159780691224244, doi101525california97805202420980010001, doi101525california97805202462320010001, openalexw2989049194, openalexw3217097258, sloan1986gradual, smith2007marine"
}

Abstract A large dinosaur bone bed has been investigated in the Udurchukan Formation (?late Maastrichtian) at Blagoveschensk, Far Eastern Russia. The observed mixture of unstratified fine and coarse sediments in the bone bed is typical for sediment-gravity-flow deposits. It is postulated that sediment gravity flows, originating from the uplifted areas at the borders of the Zeya-Bureya Basin, reworked the dinosaur bones and teeth as a monodominant bone bed. Fossils of the lambeosaurine Amurosaurus riabinini form >90% of the recovered material. The low number of associated skeletal elements at Blagoveschensk indicates that the carcasses were disarticulated well before reworking. Although shed theropod teeth have been found in the bone bed, <2% of the bones exhibit potential tooth marks; scavenging activity was therefore limited, or scavengers had an abundance of prey at hand and did not have to actively seek out bones for nutrients. Perthotaxic features are very rare on the bones, implying that they were no...

@article{doi102110palo2006p06031r,
    author = "Lauters, Pascaline and Bolotsky, Yuri L. and Itterbeeck, Jimmy Van and Godefroit, Pascal",
    title = "Taphonomy and Age Profile of a Latest Cretaceous Dinosaur Bone Bed in Far Eastern Russia",
    year = "2008",
    journal = "Palaios",
    abstract = "Abstract A large dinosaur bone bed has been investigated in the Udurchukan Formation (?late Maastrichtian) at Blagoveschensk, Far Eastern Russia. The observed mixture of unstratified fine and coarse sediments in the bone bed is typical for sediment-gravity-flow deposits. It is postulated that sediment gravity flows, originating from the uplifted areas at the borders of the Zeya-Bureya Basin, reworked the dinosaur bones and teeth as a monodominant bone bed. Fossils of the lambeosaurine Amurosaurus riabinini form >90\% of the recovered material. The low number of associated skeletal elements at Blagoveschensk indicates that the carcasses were disarticulated well before reworking. Although shed theropod teeth have been found in the bone bed, <2\% of the bones exhibit potential tooth marks; scavenging activity was therefore limited, or scavengers had an abundance of prey at hand and did not have to actively seek out bones for nutrients. Perthotaxic features are very rare on the bones, implying that they were no...",
    url = "https://doi.org/10.2110/palo.2006.p06-031r",
    doi = "10.2110/palo.2006.p06-031r",
    openalex = "W2085377090",
    references = "doi1010160031018270900945, doi101126science2314739714, doi1016711110, doi102110palo2003p0322"
}

Although microvertebrate accumulations are commonly used for paleoecological reconstructions, taphonomic processes affecting the final taxonomic composition of an accumulation are often ignored.This research explores the effects of abiotic taphonomic processes on the taxonomic composition of terrestrial microvertebrate accumulations by comparing a floodplain and a channel lag deposit from the Maastrichtian Hell Creek Formation in eastern Montana.Distribution of skeletal elements with specific physical attributes and relative abundance of taxa correlate with the hydraulic indicators (i.e., grain size, sedimentary structures) of the depositional facies.Transport distances, hydraulic equivalencies of dominant skeletal elements, amount of hydraulic sorting and reworking, and degree of time averaging vary between deposits and significantly affect taxonomic distributions.Relative abundance data, in conjunction with chi-square test results and rank-order analysis, show that size, shape, abrasion, and taxonomic compositions vary significantly between assemblages.The finegrained assemblage is dominated by tabular, low-density elements, such as cycloid scales and fish vertebrae.Dense, equidimensional elements, such as teeth and ganoid fish scales, dominate the sandstone assemblage.Rank-order analysis results demonstrate that relative abundance of hydraulically equivalent skeletal elements from morphologically similar organisms can be compared regardless of accumulation in nonisotaphonomic deposits.Statistical comparisons were made among osteichthyans using ganoid scales, caudates using vertebrae, ornithischians using teeth, and testudinates using shell fragments.Results show that portions of the assemblage analyzed using hydrodynamically equivalent elements are not significantly different, despite different depositional environments.

@article{doi102110palo2007p07006r,
    author = "Wilson, Laura E.",
    title = "Comparative Taphonomy and Paleoecological Reconstruction of Two Microvertebrate Accumulations from the Late Cretaceous Hell Creek Formation (Maastrichtian), Eastern Montana",
    year = "2008",
    journal = "Palaios",
    abstract = "Although microvertebrate accumulations are commonly used for paleoecological reconstructions, taphonomic processes affecting the final taxonomic composition of an accumulation are often ignored.This research explores the effects of abiotic taphonomic processes on the taxonomic composition of terrestrial microvertebrate accumulations by comparing a floodplain and a channel lag deposit from the Maastrichtian Hell Creek Formation in eastern Montana.Distribution of skeletal elements with specific physical attributes and relative abundance of taxa correlate with the hydraulic indicators (i.e., grain size, sedimentary structures) of the depositional facies.Transport distances, hydraulic equivalencies of dominant skeletal elements, amount of hydraulic sorting and reworking, and degree of time averaging vary between deposits and significantly affect taxonomic distributions.Relative abundance data, in conjunction with chi-square test results and rank-order analysis, show that size, shape, abrasion, and taxonomic compositions vary significantly between assemblages.The finegrained assemblage is dominated by tabular, low-density elements, such as cycloid scales and fish vertebrae.Dense, equidimensional elements, such as teeth and ganoid fish scales, dominate the sandstone assemblage.Rank-order analysis results demonstrate that relative abundance of hydraulically equivalent skeletal elements from morphologically similar organisms can be compared regardless of accumulation in nonisotaphonomic deposits.Statistical comparisons were made among osteichthyans using ganoid scales, caudates using vertebrae, ornithischians using teeth, and testudinates using shell fragments.Results show that portions of the assemblage analyzed using hydrodynamically equivalent elements are not significantly different, despite different depositional environments.",
    url = "https://doi.org/10.2110/palo.2007.p07-006r",
    doi = "10.2110/palo.2007.p07-006r",
    openalex = "W2098265913",
    references = "crossref2008the"
}

Dracorex hogwartsia (juvenile) and Stygimoloch spinifer (subadult) are reinterpreted as younger growth stages of Pachycephalosaurus wyomingensis (adult). This synonymy reduces the number of pachycephalosaurid taxa from the Upper Cretaceous of North America and demonstrates the importance of cranial ontogeny in evaluating dinosaur diversity and taxonomy. These growth stages reflect a continuum rather than specific developmental steps defined by "known" terminal morphologies.

@article{doi101371journalpone0007626,
    author = "Horner, John R. and Goodwin, Mark B.",
    title = "Extreme Cranial Ontogeny in the Upper Cretaceous Dinosaur Pachycephalosaurus",
    year = "2009",
    journal = "PLoS ONE",
    abstract = {Dracorex hogwartsia (juvenile) and Stygimoloch spinifer (subadult) are reinterpreted as younger growth stages of Pachycephalosaurus wyomingensis (adult). This synonymy reduces the number of pachycephalosaurid taxa from the Upper Cretaceous of North America and demonstrates the importance of cranial ontogeny in evaluating dinosaur diversity and taxonomy. These growth stages reflect a continuum rather than specific developmental steps defined by "known" terminal morphologies.},
    url = "https://doi.org/10.1371/journal.pone.0007626",
    doi = "10.1371/journal.pone.0007626",
    openalex = "W2094698530",
    references = "doi10100210970177200099999999aiddvdy107330co2f, doi101002jmor10575, doi1010079781489953919, doi101007978148995740520, doi101029sc005p0175, doi101093sysbio24137, doi101111j109636421997tb00340x, doi101111j174966321940tb57047x, doi1016660094837320040300253chopom20co2, doi1016660094837320050310291teafot20co2, doi10167102724634200828134ooceit20co2, doi1023072532815, openalexw2259418280"
}

@article{horner2011dinosaur,
    author = "Horner, John R. and Goodwin, Mark B. and Myhrvold, Nathan",
    title = "Dinosaur Census Reveals Abundant Tyrannosaurus and Rare Ontogenetic Stages in the Upper Cretaceous Hell Creek Formation (Maastrichtian), Montana, USA",
    year = "2011",
    journal = "PLoS ONE",
    url = "https://doi.org/10.1371/journal.pone.0016574",
    doi = "10.1371/journal.pone.0016574",
    number = "2",
    pages = "e16574",
    volume = "6"
}

Abstract The global Late Maastrichtian non-avian dinosaur apparent biodiversity is extensively surveyed for the first time. It amounts to 104 species (including unnamed forms) in 2010. The real biodiversity being obscured by taphonomical biases and the scarcity of the continental fossil record, a species-area relationship is used to estimate it. The results show that several hundreds (between 628 and 1078) non-avian dinosaur species were alive in the Late Maastrichtian, which is almost an order of magnitude above previous estimates. Because of the complex Late Cretaceous palaeobiogeography, discussions about dinosaur extinction should be based on this estimated real global biodiversity, not on the apparent biodiversity of a single area. Given the mean duration of dinosaur genera (7.7 Ma), the presence of so many dinosaur species in the Latest Cretaceous is consistent with the termination of most lineages at the Cretaceous-Tertiary boundary (the Late Maastrichtian sub-stage is 2.8 m.y. long). The Late Maastrichtian dinosaurian biodiversity is therefore consistent with the sudden extinction of the group following the Chicxulub impact.

@article{doi102113gssgfbull1836547,
    author = "Lœuff, Jean Le",
    title = "Paleobiogeography and biodiversity of Late Maastrichtian dinosaurs: how many dinosaur species went extinct at the Cretaceous-Tertiary boundary?",
    year = "2012",
    journal = "Bulletin de la Société Géologique de France",
    abstract = "Abstract The global Late Maastrichtian non-avian dinosaur apparent biodiversity is extensively surveyed for the first time. It amounts to 104 species (including unnamed forms) in 2010. The real biodiversity being obscured by taphonomical biases and the scarcity of the continental fossil record, a species-area relationship is used to estimate it. The results show that several hundreds (between 628 and 1078) non-avian dinosaur species were alive in the Late Maastrichtian, which is almost an order of magnitude above previous estimates. Because of the complex Late Cretaceous palaeobiogeography, discussions about dinosaur extinction should be based on this estimated real global biodiversity, not on the apparent biodiversity of a single area. Given the mean duration of dinosaur genera (7.7 Ma), the presence of so many dinosaur species in the Latest Cretaceous is consistent with the termination of most lineages at the Cretaceous-Tertiary boundary (the Late Maastrichtian sub-stage is 2.8 m.y. long). The Late Maastrichtian dinosaurian biodiversity is therefore consistent with the sudden extinction of the group following the Chicxulub impact.",
    url = "https://doi.org/10.2113/gssgfbull.183.6.547",
    doi = "10.2113/gssgfbull.183.6.547",
    openalex = "W2129835365",
    references = "doi101086379695"
}

ABSTRACT The vertebrate fauna of the Cloverly Formation has been studied for more than 75 years, but remains poorly sampled and incompletely understood. We undertook an extensive survey of the formation that resulted in the discovery of several new, highly productive vertebrate microfossil bonebeds (VMBs). Comprehensive sampling of these and other sites has nearly doubled the known vertebrate diversity of the Cloverly Formation. In addition to the comparatively well-known dinosaurs, this augmented faunal list includes hybodontoid sharks, numerous bony fishes, three lissamphibian lineages, lizards, multiple crocodylians, and several new mammal occurrences. The known Cloverly vertebrate fauna now more closely resembles those of other late Early Cretaceous formations in North America, indicating broad similarities across wide geographic areas at this time. In addition, this work underscores the important role VMBs can play in areas previously studied primarily through surface prospecting and quarrying, especially for assessing paleoecology and species diversity.

@article{doi101080027246342012717567,
    author = "Oreska, Matthew P. J. and Carrano, Matthew T. and Dzikiewicz, Katherine M.",
    title = "Vertebrate paleontology of the Cloverly Formation (Lower Cretaceous), I: faunal composition, biogeographic relationships, and sampling",
    year = "2013",
    journal = "Journal of Vertebrate Paleontology",
    abstract = "ABSTRACT The vertebrate fauna of the Cloverly Formation has been studied for more than 75 years, but remains poorly sampled and incompletely understood. We undertook an extensive survey of the formation that resulted in the discovery of several new, highly productive vertebrate microfossil bonebeds (VMBs). Comprehensive sampling of these and other sites has nearly doubled the known vertebrate diversity of the Cloverly Formation. In addition to the comparatively well-known dinosaurs, this augmented faunal list includes hybodontoid sharks, numerous bony fishes, three lissamphibian lineages, lizards, multiple crocodylians, and several new mammal occurrences. The known Cloverly vertebrate fauna now more closely resembles those of other late Early Cretaceous formations in North America, indicating broad similarities across wide geographic areas at this time. In addition, this work underscores the important role VMBs can play in areas previously studied primarily through surface prospecting and quarrying, especially for assessing paleoecology and species diversity.",
    url = "https://doi.org/10.1080/02724634.2012.717567",
    doi = "10.1080/02724634.2012.717567",
    openalex = "W1977535708",
    references = "cifelli1998triconodont, doi10100797814684216682, doi101007bf00344966, doi101016jcretres200802004, doi101038114085a0, doi10108002724634199810011048, doi101080027246342012671204, doi101086273307, doi101093nqs5vi146318i, doi101098rstb19940091, doi1016660094837336180, doi102110pec95520097, doi102475ajss319111253, doi105281zenodo16171435, doi107312kiel11918, openalexw2246336267, openalexw3215057009, sánchezhernández2007dinosaurs"
}

A high-resolution biostratigraphic analysis of 287 dinosaurian macrofossils and 138 bonebeds in the Edmonton Group (Upper Cretaceous) of southern Alberta provides evidence for at least three dinosaurian assemblage zones in the Horseshoe Canyon Formation (HCFm). From bottom to top the zones comprise unique assemblages of ornithischians and are named as follows: (1) Edmontosaurus regalis – Pachyrhinosaurus canadensis (lower zone); (2) Hypacrosaurus altispinus – Saurolophus osborni (middle zone); and (3) Eotriceratops xerinsularis (upper zone). Whereas the lower and middle zones are well defined and based on abundant specimens, the validity of the uppermost zone (E. xerinsularis) is tentative because it is based on a single specimen and the absence of dinosaur taxa from lower in section. The transition from the lower to the middle zone coincides with the replacement of a warm-and-wet saturated deltaic setting by a cooler, coastal-plain landscape, characterized by seasonal rainfall and better-drained substrates. Whereas changes in rainfall and substrate drainage appear to have influenced the faunal change, changes in mean annual temperature and proximity to shoreline appear to have had little influence on faunal change. We speculate that the faunal change between the middle and upper zones also resulted from a change in climate, with ornithischian dinosaurs responding to the re-establishment of wetter-and-warmer climates and poorly-drained substrates. Compared with the shorter-duration and climatically-consistent dinosaurian assemblage zones in the older Dinosaur Park Formation of southern Alberta, HCFm assemblage zones record long-term morphological stasis in dinosaurs. Furthermore, the coincidence of faunal and paleoenvironmental changes in the HCFm suggest climate-change-driven dinosaur migrations into and out of the region.

@article{doi101139cjes20120185,
    author = "Eberth, David A. and Evans, David C. and Brinkman, Donald B. and Therrien, François and Tanke, Darren H. and Russell, Loris S.",
    title = "Dinosaur biostratigraphy of the Edmonton Group (Upper Cretaceous), Alberta, Canada: evidence for climate influence",
    year = "2013",
    journal = "Canadian Journal of Earth Sciences",
    abstract = "A high-resolution biostratigraphic analysis of 287 dinosaurian macrofossils and 138 bonebeds in the Edmonton Group (Upper Cretaceous) of southern Alberta provides evidence for at least three dinosaurian assemblage zones in the Horseshoe Canyon Formation (HCFm). From bottom to top the zones comprise unique assemblages of ornithischians and are named as follows: (1) Edmontosaurus regalis – Pachyrhinosaurus canadensis (lower zone); (2) Hypacrosaurus altispinus – Saurolophus osborni (middle zone); and (3) Eotriceratops xerinsularis (upper zone). Whereas the lower and middle zones are well defined and based on abundant specimens, the validity of the uppermost zone (E. xerinsularis) is tentative because it is based on a single specimen and the absence of dinosaur taxa from lower in section. The transition from the lower to the middle zone coincides with the replacement of a warm-and-wet saturated deltaic setting by a cooler, coastal-plain landscape, characterized by seasonal rainfall and better-drained substrates. Whereas changes in rainfall and substrate drainage appear to have influenced the faunal change, changes in mean annual temperature and proximity to shoreline appear to have had little influence on faunal change. We speculate that the faunal change between the middle and upper zones also resulted from a change in climate, with ornithischian dinosaurs responding to the re-establishment of wetter-and-warmer climates and poorly-drained substrates. Compared with the shorter-duration and climatically-consistent dinosaurian assemblage zones in the older Dinosaur Park Formation of southern Alberta, HCFm assemblage zones record long-term morphological stasis in dinosaurs. Furthermore, the coincidence of faunal and paleoenvironmental changes in the HCFm suggest climate-change-driven dinosaur migrations into and out of the region.",
    url = "https://doi.org/10.1139/cjes-2012-0185",
    doi = "10.1139/cjes-2012-0185",
    openalex = "W2157353435",
    references = "doi101016jpalaeo201206024, doi101016jpalaeo201206027, doi101017cbo9780511536045020, doi101098rspb20090352, doi101126science1177265, doi1011270078042120120020, doi101139e10005, doi101139e11017, doi101139e72031, doi101139e93016, doi10130683d923ed16c711d78645000102c1865d, doi101371journalpone0016574, doi101371journalpone0025186, doi104202app20110033, doi105281zenodo3725717, horner2011dinosaur, openalexw2989049194, sternberg1926notes"
}

Detailed understanding of ecosystem decline and recovery attending the Cretaceous-Paleogene boundary (KPB) mass extinctions is hindered by limited constraints on the pace and tempo of environmental events near the boundary. To mitigate this shortcoming, high-resolution 40Ar/39Ar geochronology was performed on tephras intercalated between fossiliferous terrestrial sediments of the upper Hell Creek and lower Fort Union Formations in the western Williston Basin of northeastern Montana (USA). Tephra samples were collected from 10 stratigraphic sections spanning an area of ~5000 km2. Several distinctive tephras can be correlated between sections separated spatially by as much as ~60 km. The tephras are thin distal deposits generally preserved only in lignite beds, which are interbedded with clastic deposits yielding vertebrate faunas of Lancian (late Maastrichtian) to Torrejonian (early Danian) North American Land Mammal Ages. Sanidine from 15 tephra samples was analyzed in 1649 total fusion experiments (1597 on single crystals) and 12 incremental heating analyses of multigrain aliquots. Ages were determined for 13 distinct tephras, ranging from 66.289 ± 0.051 to 64.866 ± 0.023 Ma, including only analytical uncertainties. This level of precision is sufficient to resolve the ages of all of the coal beds that have served as a basis for a regional stratigraphic framework. The data confirm that the Hell Creek-Fort Union formational contact is diachronous, and further support the age of the KPB impact layer at 66.043 ± 0.010 Ma (or ± 0.043 Ma considering systematic uncertainties). Application of the new results to previous magnetostratigraphic data indicates an appreciably compressed time interval between the base of chron C29r and the top of chron C28r, with a maximum duration estimate of 1.421 ± 0.066 Ma. Most notable is the implied brevity of chron C29r, with a maximum estimate of 457 ± 54 ka, and possibly as brief as 345 ± 38 ka, compared to the 710 ka estimate from the Geologic Time Scale 2012 (GTS2012). Further, application of new results to terrestrial biostratigraphy adds higher precision to the timing and tempo of biotic change before and after the KPB. Our results indicate that the timing of pre-KPB ecological decline is constrained to the last ~200 ka of the Cretaceous, adding further support to the press-pulse extinction hypothesis. Additionally, the duration of the depauperate basal Paleogene Puercan 1 disas ter fauna is confined to a 70 ka interval. Faunal recovery in this region, indicated by the appearance of primitive members of the placental mammal radiation and the restoration of taxonomic richness and evenness, occurred within ~900 ka after the KPB. These results show that biotic recovery after the mass extinction in the terrestrial realm was more rapid than in the marine.

@article{doi101130b310761,
    author = "Sprain, Courtney J. and Renne, Paul R. and Wilson, Gregory P. and Clemens, W. A.",
    title = "High-resolution chronostratigraphy of the terrestrial Cretaceous-Paleogene transition and recovery interval in the Hell Creek region, Montana",
    year = "2014",
    journal = "Geological Society of America Bulletin",
    abstract = "Detailed understanding of ecosystem decline and recovery attending the Cretaceous-Paleogene boundary (KPB) mass extinctions is hindered by limited constraints on the pace and tempo of environmental events near the boundary. To mitigate this shortcoming, high-resolution 40Ar/39Ar geochronology was performed on tephras intercalated between fossiliferous terrestrial sediments of the upper Hell Creek and lower Fort Union Formations in the western Williston Basin of northeastern Montana (USA). Tephra samples were collected from 10 stratigraphic sections spanning an area of \textasciitilde 5000 km2. Several distinctive tephras can be correlated between sections separated spatially by as much as \textasciitilde 60 km. The tephras are thin distal deposits generally preserved only in lignite beds, which are interbedded with clastic deposits yielding vertebrate faunas of Lancian (late Maastrichtian) to Torrejonian (early Danian) North American Land Mammal Ages. Sanidine from 15 tephra samples was analyzed in 1649 total fusion experiments (1597 on single crystals) and 12 incremental heating analyses of multigrain aliquots. Ages were determined for 13 distinct tephras, ranging from 66.289 ± 0.051 to 64.866 ± 0.023 Ma, including only analytical uncertainties. This level of precision is sufficient to resolve the ages of all of the coal beds that have served as a basis for a regional stratigraphic framework. The data confirm that the Hell Creek-Fort Union formational contact is diachronous, and further support the age of the KPB impact layer at 66.043 ± 0.010 Ma (or ± 0.043 Ma considering systematic uncertainties). Application of the new results to previous magnetostratigraphic data indicates an appreciably compressed time interval between the base of chron C29r and the top of chron C28r, with a maximum duration estimate of 1.421 ± 0.066 Ma. Most notable is the implied brevity of chron C29r, with a maximum estimate of 457 ± 54 ka, and possibly as brief as 345 ± 38 ka, compared to the 710 ka estimate from the Geologic Time Scale 2012 (GTS2012). Further, application of new results to terrestrial biostratigraphy adds higher precision to the timing and tempo of biotic change before and after the KPB. Our results indicate that the timing of pre-KPB ecological decline is constrained to the last \textasciitilde 200 ka of the Cretaceous, adding further support to the press-pulse extinction hypothesis. Additionally, the duration of the depauperate basal Paleogene Puercan 1 disas ter fauna is confined to a 70 ka interval. Faunal recovery in this region, indicated by the appearance of primitive members of the placental mammal radiation and the restoration of taxonomic richness and evenness, occurred within \textasciitilde 900 ka after the KPB. These results show that biotic recovery after the mass extinction in the terrestrial realm was more rapid than in the marine.",
    url = "https://doi.org/10.1130/b31076.1",
    doi = "10.1130/b31076.1",
    openalex = "W2044128051",
    references = "alvarez1980extraterrestrial, archibald1982upper, doi101016jepsl200707011, doi101016jgca201106021, doi101016jpalaeo200709016, doi1010292008jb005644, doi101073pnas0234701100, doi101073pnas802627, doi101126science1154339, doi101126science1177265, doi101126science1230492, doi101126science1483667220, doi101126science22346411177, doi10113000917613198210153ucbamh20co2, doi10113000917613198614279ssaedt20co2, doi101146annurevecolsys35021103105715, doi10166612041, doi1023073514678, openalexw610180004, rigby1987dinosaurs"
}

Megaherbivorous dinosaurs were exceptionally diverse on the Late Cretaceous island continent of Laramidia, and a growing body of evidence suggests that this diversity was facilitated by dietary niche partitioning. We test this hypothesis using the fossil megaherbivore assemblage from the Dinosaur Park Formation (upper Campanian) of Alberta as a model. Comparative tooth morphology and wear, including the first use of quantitative dental microwear analysis in the context of Cretaceous palaeosynecology, are used to infer the mechanical properties of the foods these dinosaurs consumed. The phylliform teeth of ankylosaurs were poorly adapted for habitually processing high-fibre plant matter. Nevertheless, ankylosaur diets were likely more varied than traditionally assumed: the relatively large, bladed teeth of nodosaurids would have been better adapted to processing a tougher, more fibrous diet than the smaller, cusp-like teeth of ankylosaurids. Ankylosaur microwear is characterized by a preponderance of pits and scratches, akin to modern mixed feeders, but offers no support for interspecific dietary differences. The shearing tooth batteries of ceratopsids are much better adapted to high-fibre herbivory, attested by their scratch-dominated microwear signature. There is tentative microwear evidence to suggest differences in the feeding habits of centrosaurines and chasmosaurines, but statistical support is not significant. The tooth batteries of hadrosaurids were capable of both shearing and crushing functions, suggestive of a broad dietary range. Their microwear signal overlaps broadly with that of ankylosaurs, and suggests possible dietary differences between hadrosaurines and lambeosaurines. Tooth wear evidence further indicates that all forms considered here exhibited some degree of masticatory propaliny. Our findings reveal that tooth morphology and wear exhibit different, but complimentary, dietary signals that combine to support the hypothesis of dietary niche partitioning. The inferred mechanical and dietary patterns appear constant over the 1.5 Myr timespan of the Dinosaur Park Formation megaherbivore chronofauna, despite continual species turnover.

@article{doi101371journalpone0098605,
    author = "Mallon, Jordan C. and Anderson, Jason S.",
    title = "The Functional and Palaeoecological Implications of Tooth Morphology and Wear for the Megaherbivorous Dinosaurs from the Dinosaur Park Formation (Upper Campanian) of Alberta, Canada",
    year = "2014",
    journal = "PLoS ONE",
    abstract = "Megaherbivorous dinosaurs were exceptionally diverse on the Late Cretaceous island continent of Laramidia, and a growing body of evidence suggests that this diversity was facilitated by dietary niche partitioning. We test this hypothesis using the fossil megaherbivore assemblage from the Dinosaur Park Formation (upper Campanian) of Alberta as a model. Comparative tooth morphology and wear, including the first use of quantitative dental microwear analysis in the context of Cretaceous palaeosynecology, are used to infer the mechanical properties of the foods these dinosaurs consumed. The phylliform teeth of ankylosaurs were poorly adapted for habitually processing high-fibre plant matter. Nevertheless, ankylosaur diets were likely more varied than traditionally assumed: the relatively large, bladed teeth of nodosaurids would have been better adapted to processing a tougher, more fibrous diet than the smaller, cusp-like teeth of ankylosaurids. Ankylosaur microwear is characterized by a preponderance of pits and scratches, akin to modern mixed feeders, but offers no support for interspecific dietary differences. The shearing tooth batteries of ceratopsids are much better adapted to high-fibre herbivory, attested by their scratch-dominated microwear signature. There is tentative microwear evidence to suggest differences in the feeding habits of centrosaurines and chasmosaurines, but statistical support is not significant. The tooth batteries of hadrosaurids were capable of both shearing and crushing functions, suggestive of a broad dietary range. Their microwear signal overlaps broadly with that of ankylosaurs, and suggests possible dietary differences between hadrosaurines and lambeosaurines. Tooth wear evidence further indicates that all forms considered here exhibited some degree of masticatory propaliny. Our findings reveal that tooth morphology and wear exhibit different, but complimentary, dietary signals that combine to support the hypothesis of dietary niche partitioning. The inferred mechanical and dietary patterns appear constant over the 1.5 Myr timespan of the Dinosaur Park Formation megaherbivore chronofauna, despite continual species turnover.",
    url = "https://doi.org/10.1371/journal.pone.0098605",
    doi = "10.1371/journal.pone.0098605",
    openalex = "W2033356851",
    references = "brinkman1990paleooecology, doi1010029780470750711, doi101002jmor10372, doi101016jpalaeo201206024, doi101017cbo9780511564345, doi101046j14429993200101070x, doi101080089129632012688589, doi101086653688, doi101093behecoarh107, doi101111j14429993200101070ppx, doi101139e78109, doi101186147267851314, doi101371journalpone0067182, doi1016690883135120010160482ttoaco20co2, doi101671027246342003231apfast20co2, doi1023072291098, doi105860choice326223, doi105962bhltitle115853, openalexw1540596182, openalexw2138825607, openalexw2183707334, openalexw575814759"
}

@article{doi101016jcretres201507007,
    author = "Fastovsky, David E. and Bercovici, Antoine",
    title = "The Hell Creek Formation and its contribution to the Cretaceous–Paleogene extinction: A short primer",
    year = "2015",
    journal = "Cretaceous Research",
    url = "https://doi.org/10.1016/j.cretres.2015.07.007",
    doi = "10.1016/j.cretres.2015.07.007",
    openalex = "W1445231874",
    references = "doi101002jgrg20086, doi10113000917613198614279ssaedt20co2"
}

Our understanding of the evolutionary transitions leading to the modern endothermic state of birds and mammals is incomplete, partly because tools available to study the thermophysiology of extinct vertebrates are limited. Here we show that clumped isotope analysis of eggshells can be used to determine body temperatures of females during periods of ovulation. Late Cretaceous titanosaurid eggshells yield temperatures similar to large modern endotherms. In contrast, oviraptorid eggshells yield temperatures lower than most modern endotherms but ∼ 6 °C higher than co-occurring abiogenic carbonates, implying that this taxon did not have thermoregulation comparable to modern birds, but was able to elevate its body temperature above environmental temperatures. Therefore, we observe no strong evidence for end-member ectothermy or endothermy in the species examined. Body temperatures for these two species indicate that variable thermoregulation likely existed among the non-avian dinosaurs and that not all dinosaurs had body temperatures in the range of that seen in modern birds.

@article{doi101038ncomms9296,
    author = "Eagle, Robert A. and Enriquez, Marcus and Grellet‐Tinner, Gerald and Pérez‐Huerta, Alberto and Hu, David L. and Tütken, Thomas and Montanari, Shaena and Loyd, S. J. and Ramírez, Pedro Dueñas and Tripati, Aradhna and Kohn, Matthew J. and Cerling, Thure E. and Chiappe, Luis M. and Eiler, John M.",
    title = "Isotopic ordering in eggshells reflects body temperatures and suggests differing thermophysiology in two Cretaceous dinosaurs",
    year = "2015",
    journal = "Nature Communications",
    abstract = "Our understanding of the evolutionary transitions leading to the modern endothermic state of birds and mammals is incomplete, partly because tools available to study the thermophysiology of extinct vertebrates are limited. Here we show that clumped isotope analysis of eggshells can be used to determine body temperatures of females during periods of ovulation. Late Cretaceous titanosaurid eggshells yield temperatures similar to large modern endotherms. In contrast, oviraptorid eggshells yield temperatures lower than most modern endotherms but ∼ 6 °C higher than co-occurring abiogenic carbonates, implying that this taxon did not have thermoregulation comparable to modern birds, but was able to elevate its body temperature above environmental temperatures. Therefore, we observe no strong evidence for end-member ectothermy or endothermy in the species examined. Body temperatures for these two species indicate that variable thermoregulation likely existed among the non-avian dinosaurs and that not all dinosaurs had body temperatures in the range of that seen in modern birds.",
    url = "https://doi.org/10.1038/ncomms9296",
    doi = "10.1038/ncomms9296",
    openalex = "W1942246699",
    references = "doi101002jms1614, doi1010160168962291900552, doi101016030096299190122s, doi101016jchemgeo200708005, doi101016jgca200405035, doi101016jgca200511014, doi101016jgca201109025, doi101016s0016703797001695, doi101073pnas1001824107, doi101126science2665186779"
}

Most dromaeosaurids were small- to medium-sized cursorial, scansorial, and arboreal, sometimes volant predators, but a comparatively small percentage grew to gigantic proportions. Only two such giant “raptors” have been described from North America. Here, we describe a new giant dromaeosaurid, Dakotaraptor steini gen. et sp. nov., from the Hell Creek Formation of South Dakota. The discovery represents the first giant dromaeosaur from the Hell Creek Formation, and the most recent in the fossil record worldwide. A row of prominent ulnar papilli or “quill knobs” on the ulna is our first clear evidence for feather quills on a large dromaeosaurid forearm and impacts evolutionary reconstructions and functional morphology of such derived, typically flight-related features. The presence of this new predator expands our record of theropod diversity in latest Cretaceous Laramidia, and radically changes paleoecological reconstructions of the Hell Creek Formation.

@article{doi1017161paleo180818764,
    author = "DePalma, Robert A. and Burnham, David A. and Martin, Larry D. and Larson, Peter L. and Bakker, Robert T.",
    title = "The first giant raptor (Theropoda: Dromaeosauridae) from the Hell Creek Formation",
    year = "2015",
    journal = "Paleontological Contributions",
    abstract = "Most dromaeosaurids were small- to medium-sized cursorial, scansorial, and arboreal, sometimes volant predators, but a comparatively small percentage grew to gigantic proportions. Only two such giant “raptors” have been described from North America. Here, we describe a new giant dromaeosaurid, Dakotaraptor steini gen. et sp. nov., from the Hell Creek Formation of South Dakota. The discovery represents the first giant dromaeosaur from the Hell Creek Formation, and the most recent in the fossil record worldwide. A row of prominent ulnar papilli or “quill knobs” on the ulna is our first clear evidence for feather quills on a large dromaeosaurid forearm and impacts evolutionary reconstructions and functional morphology of such derived, typically flight-related features. The presence of this new predator expands our record of theropod diversity in latest Cretaceous Laramidia, and radically changes paleoecological reconstructions of the Hell Creek Formation.",
    url = "https://doi.org/10.17161/paleo.1808.18764",
    doi = "10.17161/paleo.1808.18764",
    openalex = "W1844540539",
    references = "doi101002ara20206, doi101007s0011401311075, doi101017s247526300000091x, doi10103821872, doi10103845769, doi101038nature01342, doi101038nature03996, doi101126science1144066, doi101371journalpone0028964, doi101371journalpone0036790, doi101371journalpone0092022, doi102475ajss3179786, doi102475ajss319111253, doi105281zenodo1040383, doi105281zenodo16171435, openalexw1537382937, russell2002synopsis"
}

@inproceedings{andlyson2016dinosaur,
    author = "Lyson, Tyler R. and Rossetto, Gabriella and Evans, Erica S.J. and Bercovici, Antoine and Johnson, Kirk and Pearson, Dean",
    title = "DINOSAUR SKELETON OCCURRENCE IN THE LATEST CRETACEOUS (LATE MAASTRICHTIAN) HELL CREEK FORMATION OF SOUTHWESTERN NORTH DAKOTA AND SOUTHEASTERN MONTANA",
    year = "2016",
    booktitle = "Geological Society of America Abstracts with Programs",
    url = "https://doi.org/10.1130/abs/2016am-282741",
    doi = "10.1130/abs/2016am-282741"
}

Despite long-standing significance in the annals of North American stratigraphy and paleontology, key aspects of the Upper Cretaceous Judith River Formation remain poorly understood. We re-evaluate Judith River stratigraphy and propose new reference sections that both document the range of lithologies present in the type area in north-central Montana and reveal dramatic changes in facies architecture, fossil content, and rock accumulation rates that can be mapped throughout the type area and into the plains of southern Alberta and Saskatchewan. One section spans the basal contact of the Judith River Formation with marine shales of the underlying Claggett Formation. This contact, which lies along the base of the Parkman Sandstone Member of the Judith River Formation, is erosional and consistent with an episode of forced regression, contrary to previous descriptions. A second reference section spans the entire Judith River Formation. This complete section hosts a lithologic discontinuity, herein referred to as the mid-Judith discontinuity, that reflects a regional reorganization of terrestrial and marine depositional systems associated with a turnaround from regressive to transgressive deposition. The mid-Judith discontinuity correlates with the base of three backstepping marine sequences in the eastern sector of the type area and is thus interpreted as the terrestrial expression of a maximum regressive surface. This mid-Judith discontinuity defines the boundary between the new McClelland Ferry and overlying Coal Ridge Members of the Judith River Formation. The shallow marine sandstones that form the backstepping sequences represent the leading edge of the Bearpaw transgression in this region and are formalized as the new Woodhawk Member of the Judith River Formation in a third reference section. New 40Ar/39Ar ages indicate (1) that the mid-Judith discontinuity formed ∼76.2 Ma, coincident with the onset of the Bearpaw transgression in central Montana; and (2) that the Bearpaw Sea had advanced westward beyond the Judith River type area by ∼75.2 Ma, on the basis of the dating of a bentonite bed at the base of the Bearpaw Formation. These new ages also provide more confident age control for important vertebrate fossil occurrences in the Judith River Formation. Facies analysis across the mid-Judith discontinuity reveals how alluvial systems respond to regional base-level rise, which is implicit with the increase in rock accumulation rates and marine transgression. With the increase in accommodation signaled by the mid-Judith discontinuity, the alluvial system shifted in dominance from fluvial channel to overbank deposits, with greater tidal influence in channel sands, more hydromorphic and carbonaceous overbank deposits, and a higher frequency of bentonites and skeletal concentrations, suggesting higher preservation rates. These features, along with the appearance of extraformational pebbles above the discontinuity, are consistent with an upstream tectonic explanation for the addition of accommodation.

@article{doi101086684289,
    author = "Rogers, Raymond R. and Kidwell, Susan M. and Deino, Alan L. and Mitchell, James P. and Nelson, Kenneth and Thole, Jeffrey T.",
    title = "Age, Correlation, and Lithostratigraphic Revision of the Upper Cretaceous (Campanian) Judith River Formation in Its Type Area (North-Central Montana), with a Comparison of Low- and High-Accommodation Alluvial Records",
    year = "2016",
    journal = "The Journal of Geology",
    abstract = "Despite long-standing significance in the annals of North American stratigraphy and paleontology, key aspects of the Upper Cretaceous Judith River Formation remain poorly understood. We re-evaluate Judith River stratigraphy and propose new reference sections that both document the range of lithologies present in the type area in north-central Montana and reveal dramatic changes in facies architecture, fossil content, and rock accumulation rates that can be mapped throughout the type area and into the plains of southern Alberta and Saskatchewan. One section spans the basal contact of the Judith River Formation with marine shales of the underlying Claggett Formation. This contact, which lies along the base of the Parkman Sandstone Member of the Judith River Formation, is erosional and consistent with an episode of forced regression, contrary to previous descriptions. A second reference section spans the entire Judith River Formation. This complete section hosts a lithologic discontinuity, herein referred to as the mid-Judith discontinuity, that reflects a regional reorganization of terrestrial and marine depositional systems associated with a turnaround from regressive to transgressive deposition. The mid-Judith discontinuity correlates with the base of three backstepping marine sequences in the eastern sector of the type area and is thus interpreted as the terrestrial expression of a maximum regressive surface. This mid-Judith discontinuity defines the boundary between the new McClelland Ferry and overlying Coal Ridge Members of the Judith River Formation. The shallow marine sandstones that form the backstepping sequences represent the leading edge of the Bearpaw transgression in this region and are formalized as the new Woodhawk Member of the Judith River Formation in a third reference section. New 40Ar/39Ar ages indicate (1) that the mid-Judith discontinuity formed ∼76.2 Ma, coincident with the onset of the Bearpaw transgression in central Montana; and (2) that the Bearpaw Sea had advanced westward beyond the Judith River type area by ∼75.2 Ma, on the basis of the dating of a bentonite bed at the base of the Bearpaw Formation. These new ages also provide more confident age control for important vertebrate fossil occurrences in the Judith River Formation. Facies analysis across the mid-Judith discontinuity reveals how alluvial systems respond to regional base-level rise, which is implicit with the increase in rock accumulation rates and marine transgression. With the increase in accommodation signaled by the mid-Judith discontinuity, the alluvial system shifted in dominance from fluvial channel to overbank deposits, with greater tidal influence in channel sands, more hydromorphic and carbonaceous overbank deposits, and a higher frequency of bentonites and skeletal concentrations, suggesting higher preservation rates. These features, along with the appearance of extraformational pebbles above the discontinuity, are consistent with an upstream tectonic explanation for the addition of accommodation.",
    url = "https://doi.org/10.1086/684289",
    doi = "10.1086/684289",
    openalex = "W2274198338",
    references = "doi101006cres19941022, doi1010079783642859168, doi1010160031018288900855, doi101016003101829090202i, doi1010160037073891901395, doi101016003707389390022w, doi101016jgca2006061563, doi101016s0016703799002045, doi101016s0195667105800308, doi101111j136530911979tb00935x, doi101126science1154339, doi1011270078042120110011, doi101139cjes20120185, doi1016660094837336180, doi101666080251, doi1018814epiiugs2013v36i3002, doi1023071005355, eberth1990stratigraphy"
}

Troodontids are known from Asia and North America, with the most complete specimens from the Jurassic of China and the Cretaceous of Mongolia. North American troodontids are poorly known, and specimens that have been described are isolated elements or partial skeletons with limited material. A new troodontid from the upper Dinosaur Park Formation (upper Campanian) is based on partial skulls, several vertebrae, ribs, gastralia, chevrons, a sacrum, partial pelvis, and partial fore and hind limbs. It is the largest troodontid known, with an estimated height of 180 cm and length of 350 cm. Like other troodontids, it possesses an elongated ambiens process and has a horizontal ventral margin of the postacetabular process. It differs from all other derived troodontids in that the slightly retroverted pubis has a shaft that curves anteroventrally. Some specimens from the Dinosaur Park Formation previously assigned to Troodon are reassigned to the new taxon, including multiple partial crania, an associated dentary and metatarsus, and a partial skeleton. Previously undescribed elements from the lower part of the Dinosaur Park Formation are assigned to the resurrected Stenonychosaurus inequalis. Distinct stratigraphic separation of Stenonychosaurus inequalis and the new taxon indicates a replacement in troodontid fauna, similar to the turnover of large ornithischians in the same formation. The new taxon is phylogenetically more closely related to Mongolian taxa, indicating the replacement of Stenonychosaurus may have been from an earlier Asian form immigrating into North America.

@article{doi101139cjes20170031,
    author = "van der Reest, Aaron J. and Currie, Philip J.",
    title = "Troodontids (Theropoda) from the Dinosaur Park Formation, Alberta, with a description of a unique new taxon: implications for deinonychosaur diversity in North America",
    year = "2017",
    journal = "Canadian Journal of Earth Sciences",
    abstract = "Troodontids are known from Asia and North America, with the most complete specimens from the Jurassic of China and the Cretaceous of Mongolia. North American troodontids are poorly known, and specimens that have been described are isolated elements or partial skeletons with limited material. A new troodontid from the upper Dinosaur Park Formation (upper Campanian) is based on partial skulls, several vertebrae, ribs, gastralia, chevrons, a sacrum, partial pelvis, and partial fore and hind limbs. It is the largest troodontid known, with an estimated height of 180 cm and length of 350 cm. Like other troodontids, it possesses an elongated ambiens process and has a horizontal ventral margin of the postacetabular process. It differs from all other derived troodontids in that the slightly retroverted pubis has a shaft that curves anteroventrally. Some specimens from the Dinosaur Park Formation previously assigned to Troodon are reassigned to the new taxon, including multiple partial crania, an associated dentary and metatarsus, and a partial skeleton. Previously undescribed elements from the lower part of the Dinosaur Park Formation are assigned to the resurrected Stenonychosaurus inequalis. Distinct stratigraphic separation of Stenonychosaurus inequalis and the new taxon indicates a replacement in troodontid fauna, similar to the turnover of large ornithischians in the same formation. The new taxon is phylogenetically more closely related to Mongolian taxa, indicating the replacement of Stenonychosaurus may have been from an earlier Asian form immigrating into North America.",
    url = "https://doi.org/10.1139/cjes-2017-0031",
    doi = "10.1139/cjes-2017-0031",
    openalex = "W2742325356",
    references = "doi101007s0011401411439, doi101007s1143400900096, doi101016jpalaeo201206024, doi101016jpalaeo201206027, doi101038415780a, doi101038nature02898, doi101038ncomms4289, doi101038ncomms4788, doi1010800272463420161269539, doi101139e93187, doi1012066481, doi1012067481, doi101371journalpone0024487, doi101371journalpone0054329, doi101371journalpone0093190, doi1016710272463420072787antdtf20co2, doi105860choice435902, doi105962p339375, openalexw2597671315"
}

Interbasinal stratigraphic correlation provides the foundation for all consequent continental-scale geological and paleontological analyses. Correlation requires synthesis of lithostratigraphic, biostratigraphic and geochronologic data, and must be periodically updated to accord with advances in dating techniques, changing standards for radiometric dates, new stratigraphic concepts, hypotheses, fossil specimens, and field data. Outdated or incorrect correlation exposes geological and paleontological analyses to potential error. The current work presents a high-resolution stratigraphic chart for terrestrial Late Cretaceous units of North America, combining published chronostratigraphic, lithostratigraphic, and biostratigraphic data. 40Ar / 39Ar radiometric dates are newly recalibrated to both current standard and decay constant pairings. Revisions to the stratigraphic placement of most units are slight, but important changes are made to the proposed correlations of the Aguja and Javelina formations, Texas, and recalibration corrections in particular affect the relative age positions of the Belly River Group, Alberta; Judith River Formation, Montana; Kaiparowits Formation, Utah; and Fruitland and Kirtland formations, New Mexico. The stratigraphic ranges of selected clades of dinosaur species are plotted on the chronostratigraphic framework, with some clades comprising short-duration species that do not overlap stratigraphically with preceding or succeeding forms. This is the expected pattern that is produced by an anagenetic mode of evolution, suggesting that true branching (speciation) events were rare and may have geographic significance. The recent hypothesis of intracontinental latitudinal provinciality of dinosaurs is shown to be affected by previous stratigraphic miscorrelation. Rapid stepwise acquisition of display characters in many dinosaur clades, in particular chasmosaurine ceratopsids, suggests that they may be useful for high resolution biostratigraphy.

@article{doi101371journalpone0188426,
    author = "Fowler, Denver Warwick",
    title = "Revised geochronology, correlation, and dinosaur stratigraphic ranges of the Santonian-Maastrichtian (Late Cretaceous) formations of the Western Interior of North America.",
    year = "2017",
    journal = "PloS one",
    abstract = "Interbasinal stratigraphic correlation provides the foundation for all consequent continental-scale geological and paleontological analyses. Correlation requires synthesis of lithostratigraphic, biostratigraphic and geochronologic data, and must be periodically updated to accord with advances in dating techniques, changing standards for radiometric dates, new stratigraphic concepts, hypotheses, fossil specimens, and field data. Outdated or incorrect correlation exposes geological and paleontological analyses to potential error. The current work presents a high-resolution stratigraphic chart for terrestrial Late Cretaceous units of North America, combining published chronostratigraphic, lithostratigraphic, and biostratigraphic data. 40Ar / 39Ar radiometric dates are newly recalibrated to both current standard and decay constant pairings. Revisions to the stratigraphic placement of most units are slight, but important changes are made to the proposed correlations of the Aguja and Javelina formations, Texas, and recalibration corrections in particular affect the relative age positions of the Belly River Group, Alberta; Judith River Formation, Montana; Kaiparowits Formation, Utah; and Fruitland and Kirtland formations, New Mexico. The stratigraphic ranges of selected clades of dinosaur species are plotted on the chronostratigraphic framework, with some clades comprising short-duration species that do not overlap stratigraphically with preceding or succeeding forms. This is the expected pattern that is produced by an anagenetic mode of evolution, suggesting that true branching (speciation) events were rare and may have geographic significance. The recent hypothesis of intracontinental latitudinal provinciality of dinosaurs is shown to be affected by previous stratigraphic miscorrelation. Rapid stepwise acquisition of display characters in many dinosaur clades, in particular chasmosaurine ceratopsids, suggests that they may be useful for high resolution biostratigraphy.",
    url = "https://pmc.ncbi.nlm.nih.gov/articles/PMC5699823/",
    doi = "10.1371/journal.pone.0188426",
    openalex = "W2544476050",
    pmcid = "PMC5699823",
    pmid = "29166406",
    references = "doi1010160012821x77900607, doi101016016896228790025x, doi101016037594749090598g, doi101016jgca201006017, doi101016jgca201106021, doi101016jsedgeo200610001, doi101016s0009254197001599, doi101016s0016703799002045, doi101016s0375947497006131, doi101126science1154339, doi101130001676061952631011cotcfo20co2, doi101130b310761, doi101139e93016, doi101371journalpone0012292, doi101371journalpone0024487, doi101371journalpone0025186, doi101371journalpone0141304, doi10167102724634200727373aarolm20co2, doi105860choice514447, lehman1987late, openalexw2025327988"
}

The mass extinction at the Cretaceous- Paleogene boundary marks one of the most important biotic turnover events in Earth history. Yet, despite decades of study, the causes of the Cretaceous-Paleogene boundary crises remain under debate. An important tool that has the capacity to greatly improve our understanding of the events around the Cretaceous-Paleogene boundary is the geomagnetic polarity time scale (GPTS). The GPTS is used for age control in numerous Cretaceous-Paleogene boundary studies, including the timing of Deccan Traps volcanism, a majority of studies in marine sections, and studies on climate and ecological change across the Cretaceous-Paleogene boundary. The current calibration of the GPTS for circum- Cretaceous-Paleogene boundary polarity chrons (C30n-C28n) from the Geologic Time Scale draws heavily on astronomical tuning and uses a 40Ar/39Ar age for the Cretaceous- Paleogene boundary as a tie point that has since been shown to be 200 ka too old. Furthermore, complex sedimentation has been recorded in marine sections immediately following the Cretaceous-Paleogene boundary, which can possibly obscure orbital signals and complicate cyclostratigraphic interpretation. An independent test of the cyclostratigraphy for this time period is imperative for confidence in the astronomical time scale. Further, polarity reversal ages given in the GPTS do not include uncertainty estimates, making them unsuitable for quantitative chronometry. Recent calibrations have been attempted using U/Pb geochronology on zircons; however, U/Pb zircon dates may be biased by pre-eruptive zircon residence times of tens to hundreds of thousands of years. In this study, we provide constraints on the timing and duration of the most important circum-Cretaceous-Paleogene boundary chron, chron C29r, using high-precision 40Ar/39Ar geochronology and magnetostratigraphy on fluvial sediments from the Hell Creek region, Montana. Here, we show results for 14 new magnetostratigraphic sections, and 18 new high-precision 40Ar/39Ar dates, which together provide six independent constraints on the age of the C29r/C29n reversal and two constraints on the C30n/ C29r reversal. Together, these results show that the duration of C29r was 587 ± 53 ka, consistent with the most recent Geologic Time Scale calibration and previous U-Pb age models. We further present new geochronologic data for the Cretaceous-Paleogene boundary that provide the most precise date yet, of 66.052 ± 0.008/0.043 Ma. Integration of our results into the extensive paleontological framework for this region further provides important constraints on rates of terrestrial faunal change across the Cretaceous-Paleogene boundary.

@article{doi101130b318901,
    author = "Sprain, Courtney J. and Renne, Paul R. and Clemens, William A. and Wilson, Gregory P.",
    title = "Calibration of chron C29r: New high-precision geochronologic and paleomagnetic constraints from the Hell Creek region, Montana",
    year = "2018",
    journal = "Geological Society of America Bulletin",
    abstract = "The mass extinction at the Cretaceous- Paleogene boundary marks one of the most important biotic turnover events in Earth history. Yet, despite decades of study, the causes of the Cretaceous-Paleogene boundary crises remain under debate. An important tool that has the capacity to greatly improve our understanding of the events around the Cretaceous-Paleogene boundary is the geomagnetic polarity time scale (GPTS). The GPTS is used for age control in numerous Cretaceous-Paleogene boundary studies, including the timing of Deccan Traps volcanism, a majority of studies in marine sections, and studies on climate and ecological change across the Cretaceous-Paleogene boundary. The current calibration of the GPTS for circum- Cretaceous-Paleogene boundary polarity chrons (C30n-C28n) from the Geologic Time Scale draws heavily on astronomical tuning and uses a 40Ar/39Ar age for the Cretaceous- Paleogene boundary as a tie point that has since been shown to be 200 ka too old. Furthermore, complex sedimentation has been recorded in marine sections immediately following the Cretaceous-Paleogene boundary, which can possibly obscure orbital signals and complicate cyclostratigraphic interpretation. An independent test of the cyclostratigraphy for this time period is imperative for confidence in the astronomical time scale. Further, polarity reversal ages given in the GPTS do not include uncertainty estimates, making them unsuitable for quantitative chronometry. Recent calibrations have been attempted using U/Pb geochronology on zircons; however, U/Pb zircon dates may be biased by pre-eruptive zircon residence times of tens to hundreds of thousands of years. In this study, we provide constraints on the timing and duration of the most important circum-Cretaceous-Paleogene boundary chron, chron C29r, using high-precision 40Ar/39Ar geochronology and magnetostratigraphy on fluvial sediments from the Hell Creek region, Montana. Here, we show results for 14 new magnetostratigraphic sections, and 18 new high-precision 40Ar/39Ar dates, which together provide six independent constraints on the age of the C29r/C29n reversal and two constraints on the C30n/ C29r reversal. Together, these results show that the duration of C29r was 587 ± 53 ka, consistent with the most recent Geologic Time Scale calibration and previous U-Pb age models. We further present new geochronologic data for the Cretaceous-Paleogene boundary that provide the most precise date yet, of 66.052 ± 0.008/0.043 Ma. Integration of our results into the extensive paleontological framework for this region further provides important constraints on rates of terrestrial faunal change across the Cretaceous-Paleogene boundary.",
    url = "https://doi.org/10.1130/b31890.1",
    doi = "10.1130/b31890.1",
    openalex = "W2802628992",
    references = "archibald1982upper, doi101007s1091400569434, doi101016003192017790108x, doi101016jepsl200801015, doi101016s0009254197001599, doi101016s0012821x03005570, doi101017cbo9780511536045, doi10102994jb03098, doi1010510004636120041335, doi101098rspa19530064, doi101111j1365246x1980tb02601x, doi101111j1365246x1990tb05683x, doi101111sed12405, doi101126science1154339, doi101126science1177265, doi10113000917613198210153ucbamh20co2, doi10113000917613198614279ssaedt20co2, doi101130b310761, doi1023073514678, doi103133pp776"
}

Perinatal specimens of hadrosaurids discovered in the late 1970's by field crews from Princeton University were significant in providing evidence of the early ontogenetic stages in North American dinosaurs. These specimens from the Campanian (Upper Cretaceous) Two Medicine Formation of Montana consist of over a dozen skeletons referable to the saurolophine hadrosaurid Maiasaura peeblesorum, but never fully figured or described. Here, we provide a more complete documentation of the morphology of these specimens, along with an examination of variation during a large span of the development of saurolophine hadrosaurids. Many ontogenetic changes in the available facial and mandibular elements are associated with the progressive elongation of the preorbital region of the skull and mandible. In the postcranium, limb bones change nearly isometrically, with exception of certain elements of the forelimb. Some cranial and postcranial characters commonly used for inferring hadrosaurid phylogenetic relationships remain invariable during the ontogeny of M. peeblesorum. This indicates that early ontogenetic stages may still provide a limited amount of character information useful for systematics and phylogenetic inference.

@article{doi107717peerj4734,
    author = "Prieto‐Márquez, Albert and Guenther, Merrilee F.",
    title = "Perinatal specimens of Maiasaura from the Upper Cretaceous of Montana (USA): insights into the early ontogeny of saurolophine hadrosaurid dinosaurs",
    year = "2018",
    journal = "PeerJ",
    abstract = "Perinatal specimens of hadrosaurids discovered in the late 1970's by field crews from Princeton University were significant in providing evidence of the early ontogenetic stages in North American dinosaurs. These specimens from the Campanian (Upper Cretaceous) Two Medicine Formation of Montana consist of over a dozen skeletons referable to the saurolophine hadrosaurid Maiasaura peeblesorum, but never fully figured or described. Here, we provide a more complete documentation of the morphology of these specimens, along with an examination of variation during a large span of the development of saurolophine hadrosaurids. Many ontogenetic changes in the available facial and mandibular elements are associated with the progressive elongation of the preorbital region of the skull and mandible. In the postcranium, limb bones change nearly isometrically, with exception of certain elements of the forelimb. Some cranial and postcranial characters commonly used for inferring hadrosaurid phylogenetic relationships remain invariable during the ontogeny of M. peeblesorum. This indicates that early ontogenetic stages may still provide a limited amount of character information useful for systematics and phylogenetic inference.",
    url = "https://doi.org/10.7717/peerj.4734",
    doi = "10.7717/peerj.4734",
    openalex = "W2803572907",
    references = "doi101371journalpone0141304"
}

In the lead-up to the Cretaceous/Paleogene mass extinction, dinosaur diversity is argued to have been either in long-term decline, or thriving until their sudden demise. The latest Cretaceous (Campanian-Maastrichtian [83-66 Ma]) of North America provides the best record to address this debate, but even here diversity reconstructions are biased by uneven sampling. Here we combine fossil occurrences with climatic and environmental modelling to quantify latest Cretaceous North American dinosaur habitat. Ecological niche modelling shows a Campanian-to-Maastrichtian habitability decrease in areas with present-day rock-outcrop. However, a continent-wide projection demonstrates habitat stability, or even a Campanian-to-Maastrichtian increase, that is not preserved. This reduction of the spatial sampling window resulted from formation of the proto-Rocky Mountains and sea-level regression. We suggest that Maastrichtian North American dinosaur diversity is therefore likely to be underestimated, with the apparent decline a product of sampling bias, and not due to a climatically-driven decrease in habitability as previously hypothesised.

@article{doi101038s41467019089972,
    author = "Chiarenza, Alfio Alessandro and Mannion, Philip D. and Lunt, Daniel J. and Farnsworth, Alex and Jones, Lewis A. and Kelland, Sarah-Jane and Allison, Peter A.",
    title = "Ecological niche modelling does not support climatically-driven dinosaur diversity decline before the Cretaceous/Paleogene mass extinction",
    year = "2019",
    journal = "Nature Communications",
    abstract = "In the lead-up to the Cretaceous/Paleogene mass extinction, dinosaur diversity is argued to have been either in long-term decline, or thriving until their sudden demise. The latest Cretaceous (Campanian-Maastrichtian [83-66 Ma]) of North America provides the best record to address this debate, but even here diversity reconstructions are biased by uneven sampling. Here we combine fossil occurrences with climatic and environmental modelling to quantify latest Cretaceous North American dinosaur habitat. Ecological niche modelling shows a Campanian-to-Maastrichtian habitability decrease in areas with present-day rock-outcrop. However, a continent-wide projection demonstrates habitat stability, or even a Campanian-to-Maastrichtian increase, that is not preserved. This reduction of the spatial sampling window resulted from formation of the proto-Rocky Mountains and sea-level regression. We suggest that Maastrichtian North American dinosaur diversity is therefore likely to be underestimated, with the apparent decline a product of sampling bias, and not due to a climatically-driven decrease in habitability as previously hypothesised.",
    url = "https://doi.org/10.1038/s41467-019-08997-2",
    doi = "10.1038/s41467-019-08997-2",
    openalex = "W2919866498",
    references = "doi101016jecolmodel201312012, doi101016jpalaeo201602033, doi101038nature15697, doi101038ncomms1815, doi101073pnas0901637106, doi101073pnas1521478113, doi10108008912969009386535, doi101111ecog03049, doi101111j13652664200601214x, doi101111j14724642201000725x, doi101111pala12329, doi101126science3287615, doi1012019781315140919, doi101371journalpone0079420, doi1018900721531, doi1023071931034, doi103897zookeys4698439, lehman1987late"
}

Modern megaherbivore community richness is limited by bottom-up controls, such as resource limitation and resultant dietary competition. However, the extent to which these same controls impacted the richness of fossil megaherbivore communities is poorly understood. The present study investigates the matter with reference to the megaherbivorous dinosaur assemblage from the middle to upper Campanian Dinosaur Park Formation of Alberta, Canada. Using a meta-analysis of 21 ecomorphological variables measured across 14 genera, contemporaneous taxa are demonstrably well-separated in ecomorphospace at the family/subfamily level. Moreover, this pattern is persistent through the approximately 1.5 Myr timespan of the formation, despite continual species turnover, indicative of underlying structural principles imposed by long-term ecological competition. After considering the implications of ecomorphology for megaherbivorous dinosaur diet, it is concluded that competition structured comparable megaherbivorous dinosaur communities throughout the Late Cretaceous of western North America.

@article{doi101038s41598019517095,
    author = "Mallon, Jordan C.",
    title = "Competition structured a Late Cretaceous megaherbivorous dinosaur assemblage",
    year = "2019",
    journal = "Scientific Reports",
    abstract = "Modern megaherbivore community richness is limited by bottom-up controls, such as resource limitation and resultant dietary competition. However, the extent to which these same controls impacted the richness of fossil megaherbivore communities is poorly understood. The present study investigates the matter with reference to the megaherbivorous dinosaur assemblage from the middle to upper Campanian Dinosaur Park Formation of Alberta, Canada. Using a meta-analysis of 21 ecomorphological variables measured across 14 genera, contemporaneous taxa are demonstrably well-separated in ecomorphospace at the family/subfamily level. Moreover, this pattern is persistent through the approximately 1.5 Myr timespan of the formation, despite continual species turnover, indicative of underlying structural principles imposed by long-term ecological competition. After considering the implications of ecomorphology for megaherbivorous dinosaur diet, it is concluded that competition structured comparable megaherbivorous dinosaur communities throughout the Late Cretaceous of western North America.",
    url = "https://doi.org/10.1038/s41598-019-51709-5",
    doi = "10.1038/s41598-019-51709-5",
    openalex = "W2981425882",
    references = "doi101007978146124018114, doi101017cbo9780511565441, doi101017cbo9780511608551, doi101017cbo9780511735011, doi101086653688, doi101093biomet301281, doi101098rsos161086, doi101111j15023931200900187x, doi101139cjes20120185, doi101139e10005, doi101139e78109, doi101186147267851314, doi1012060003008220023660001aitrou20co2, doi101371journalpone0098605, doi101371journalpone0175253, doi101371journalpone0188426, doi1023073545850, doi1023075663, doi102475ajs2628975, openalexw2183707334"
}

The non-marine Horseshoe Canyon Formation (HCFm, southern Alberta) yields taxonomically diverse, late Campanian to middle Maastrichtian dinosaur assemblages that play a central role in documenting dinosaur evolution, paleoecology, and paleobiogeography leading up to the end-Cretaceous extinction. Here, we present high-precision U–Pb CA–ID–TIMS ages and the first calibrated chronostratigraphy for the HCFm using zircon grains from (1) four HCFm bentonites distributed through 129 m of section, (2) one bentonite from the underlying Bearpaw Formation, and (3) a bentonite from the overlying Battle Formation that we dated previously. In its type area, the HCFm ranges in age from 73.1–68.0 Ma. Significant paleoenvironmental and climatic changes are recorded in the formation, including (1) a transition from a warm-and-wet deltaic setting to a cooler, seasonally wet-dry coastal plain at 71.5 Ma, (2) maximum transgression of the Drumheller Marine Tongue at 70.896 ± 0.048 Ma, and (3) transition to a warm-wet alluvial plain at 69.6 Ma. The HCFm’s three mega-herbivore dinosaur assemblage zones track these changes and are calibrated as follows: Edmontosaurus regalis – Pachyrhinosaurus canadensis zone, 73.1–71.5 Ma; Hypacrosaurus altispinus – Saurolophus osborni zone, 71.5–69.6 Ma; and Eotriceratops xerinsularis zone, 69.6–68.2 Ma. The Albertosaurus Bonebed — a monodominant assemblage of tyrannosaurids in the Tolman Member — is assessed an age of 70.1 Ma. The unusual triceratopsin, Eotriceratops xerinsularis, from the Carbon Member, is assessed an age of 68.8 Ma. This chronostratigraphy is useful for refining correlations with dinosaur-bearing upper Campanian–middle Maastrichtian units in Alberta and elsewhere in North America.

@article{doi101139cjes20190019,
    author = "Eberth, David A. and Kamo, Sandra L.",
    title = "High-precision U–Pb CA–ID–TIMS dating and chronostratigraphy of the dinosaur-rich Horseshoe Canyon Formation (Upper Cretaceous, Campanian–Maastrichtian), Red Deer River valley, Alberta, Canada",
    year = "2019",
    journal = "Canadian Journal of Earth Sciences",
    abstract = "The non-marine Horseshoe Canyon Formation (HCFm, southern Alberta) yields taxonomically diverse, late Campanian to middle Maastrichtian dinosaur assemblages that play a central role in documenting dinosaur evolution, paleoecology, and paleobiogeography leading up to the end-Cretaceous extinction. Here, we present high-precision U–Pb CA–ID–TIMS ages and the first calibrated chronostratigraphy for the HCFm using zircon grains from (1) four HCFm bentonites distributed through 129 m of section, (2) one bentonite from the underlying Bearpaw Formation, and (3) a bentonite from the overlying Battle Formation that we dated previously. In its type area, the HCFm ranges in age from 73.1–68.0 Ma. Significant paleoenvironmental and climatic changes are recorded in the formation, including (1) a transition from a warm-and-wet deltaic setting to a cooler, seasonally wet-dry coastal plain at 71.5 Ma, (2) maximum transgression of the Drumheller Marine Tongue at 70.896 ± 0.048 Ma, and (3) transition to a warm-wet alluvial plain at 69.6 Ma. The HCFm’s three mega-herbivore dinosaur assemblage zones track these changes and are calibrated as follows: Edmontosaurus regalis – Pachyrhinosaurus canadensis zone, 73.1–71.5 Ma; Hypacrosaurus altispinus – Saurolophus osborni zone, 71.5–69.6 Ma; and Eotriceratops xerinsularis zone, 69.6–68.2 Ma. The Albertosaurus Bonebed — a monodominant assemblage of tyrannosaurids in the Tolman Member — is assessed an age of 70.1 Ma. The unusual triceratopsin, Eotriceratops xerinsularis, from the Carbon Member, is assessed an age of 68.8 Ma. This chronostratigraphy is useful for refining correlations with dinosaur-bearing upper Campanian–middle Maastrichtian units in Alberta and elsewhere in North America.",
    url = "https://doi.org/10.1139/cjes-2019-0019",
    doi = "10.1139/cjes-2019-0019",
    openalex = "W2979872101",
    references = "andeberth2016new, doi101007springerreference4923, doi1010160016703773902135, doi101016jchemgeo200503011, doi101016jgca200509007, doi101016jgca201006017, doi101016s0009254196000332, doi101016s0195667105800308, doi101073pnas1313334111, doi101103physrevc41889, doi101126science1154339, doi101126science1230492, doi101139cjes20120185, doi101371journalpone0188426, doi104202app20110033, doi105860choice435902, openalexw2989049194"
}

@inproceedings{andsankey2020why,
    author = "Sankey, Julia",
    title = "WHY SWEAT THE SMALL STUFF? NEW DISCOVERIES OF BABY DINOSAURS, TINY SHARKS, AND OTHER MICROVERTEBRATE FOSSILS, LATEST CRETACEOUS HELL CREEK FORMATION, NORTH DAKOTA",
    year = "2020",
    booktitle = "Geological Society of America Abstracts with Programs",
    url = "https://doi.org/10.1130/abs/2020cd-347371",
    doi = "10.1130/abs/2020cd-347371",
    openalex = "W3016779821"
}

The Cretaceous/Paleogene mass extinction, 66 Ma, included the demise of non-avian dinosaurs. Intense debate has focused on the relative roles of Deccan volcanism and the Chicxulub asteroid impact as kill mechanisms for this event. Here, we combine fossil-occurrence data with paleoclimate and habitat suitability models to evaluate dinosaur habitability in the wake of various asteroid impact and Deccan volcanism scenarios. Asteroid impact models generate a prolonged cold winter that suppresses potential global dinosaur habitats. Conversely, long-term forcing from Deccan volcanism (carbon dioxide [CO 2]-induced warming) leads to increased habitat suitability. Short-term (aerosol cooling) volcanism still allows equatorial habitability. These results support the asteroid impact as the main driver of the non-avian dinosaur extinction. By contrast, induced warming from volcanism mitigated the most extreme effects of asteroid impact, potentially reducing the extinction severity.

@article{doi101073pnas2006087117,
    author = "Chiarenza, Alfio Alessandro and Farnsworth, Alexander and Mannion, Philip D. and Lunt, Daniel J. and Valdes, Paul J. and Morgan, Joanna and Allison, Peter A.",
    title = "Asteroid impact, not volcanism, caused the end-Cretaceous dinosaur extinction",
    year = "2020",
    journal = "Proceedings of the National Academy of Sciences",
    abstract = "The Cretaceous/Paleogene mass extinction, 66 Ma, included the demise of non-avian dinosaurs. Intense debate has focused on the relative roles of Deccan volcanism and the Chicxulub asteroid impact as kill mechanisms for this event. Here, we combine fossil-occurrence data with paleoclimate and habitat suitability models to evaluate dinosaur habitability in the wake of various asteroid impact and Deccan volcanism scenarios. Asteroid impact models generate a prolonged cold winter that suppresses potential global dinosaur habitats. Conversely, long-term forcing from Deccan volcanism (carbon dioxide [CO 2]-induced warming) leads to increased habitat suitability. Short-term (aerosol cooling) volcanism still allows equatorial habitability. These results support the asteroid impact as the main driver of the non-avian dinosaur extinction. By contrast, induced warming from volcanism mitigated the most extreme effects of asteroid impact, potentially reducing the extinction severity.",
    url = "https://doi.org/10.1073/pnas.2006087117",
    doi = "10.1073/pnas.2006087117",
    openalex = "W3038551147",
    references = "alvarez1980extraterrestrial, doi101007s1091400569434, doi101016jcub201804062, doi101016s0012825200000374, doi10102993jd02553, doi101038s41467019089972, doi101073pnas1211526110, doi101073pnas1319253111, doi101111brv12128, doi101111ecog03049, doi101111j14724642201000725x, doi101111j16000587200805742x, doi101126sciadvaat4858, doi101126science1177265, doi101126science1229237, doi101126science20844481095, doi101126science21545391501, doi101126scienceaau2422, doi101126scienceaay2268, doi1011302014250315, doi1011302014250502, doi101130spe247, doi101144sp35813"
}

Abstract In the Cretaceous of North America, environmental sensitivity and habitat specialization have been hypothesized to explain the surprisingly restricted geographic ranges of many large-bodied dinosaurs. Understanding the drivers behind this are key to determining broader trends of dinosaur species and community response to climate change under greenhouse conditions. However, previous studies of this question have commonly examined only small components of the paleo-ecosystem or operated without comparison to similar modern systems from which to constrain interpretations. Here we perform a high-resolution multi-taxic δ13C and δ18O study of a Cretaceous coastal floodplain ecosystem, focusing on species interactions and paleotemperature estimation, and compare with similar data from extant systems. Bioapatite δ13C preserves predator-prey offsets between tyrannosaurs and ornithischians (large herbivorous dinosaurs), and between aquatic reptiles and fish. Large ornithischians had broadly overlapping stable isotope ranges, contrary to hypothesized niche partitioning driven by specialization on coastal or inland subhabitat use. Comparisons to a modern analogue coastal floodplain show similar patterns of ecological guild structure and aquatic-terrestrial resource interchange. Multi-taxic oxygen isotope temperature estimations yield results for the Campanian of Alberta (Canada) consistent with the few other paleotemperature proxies available, and are validated when applied for extant species from a modern coastal floodplain, suggesting that this approach is a simple and effective avenue for paleoenvironmental reconstruction. Together, these new data suggest that dinosaur niche partitioning was more complex than previously hypothesized, and provide a framework for future research on dinosaur-dominated Mesozoic floodplain communities.

@article{doi101130g473991,
    author = "Cullen, Thomas M. and Longstaffe, Fred J. and Wortmann, Ulrich G. and Huang, L. and Fanti, Federico and Goodwin, Mark B. and Ryan, Michael J. and Evans, David C.",
    title = "Large-scale stable isotope characterization of a Late Cretaceous dinosaur-dominated ecosystem",
    year = "2020",
    journal = "Geology",
    abstract = "Abstract In the Cretaceous of North America, environmental sensitivity and habitat specialization have been hypothesized to explain the surprisingly restricted geographic ranges of many large-bodied dinosaurs. Understanding the drivers behind this are key to determining broader trends of dinosaur species and community response to climate change under greenhouse conditions. However, previous studies of this question have commonly examined only small components of the paleo-ecosystem or operated without comparison to similar modern systems from which to constrain interpretations. Here we perform a high-resolution multi-taxic δ13C and δ18O study of a Cretaceous coastal floodplain ecosystem, focusing on species interactions and paleotemperature estimation, and compare with similar data from extant systems. Bioapatite δ13C preserves predator-prey offsets between tyrannosaurs and ornithischians (large herbivorous dinosaurs), and between aquatic reptiles and fish. Large ornithischians had broadly overlapping stable isotope ranges, contrary to hypothesized niche partitioning driven by specialization on coastal or inland subhabitat use. Comparisons to a modern analogue coastal floodplain show similar patterns of ecological guild structure and aquatic-terrestrial resource interchange. Multi-taxic oxygen isotope temperature estimations yield results for the Campanian of Alberta (Canada) consistent with the few other paleotemperature proxies available, and are validated when applied for extant species from a modern coastal floodplain, suggesting that this approach is a simple and effective avenue for paleoenvironmental reconstruction. Together, these new data suggest that dinosaur niche partitioning was more complex than previously hypothesized, and provide a framework for future research on dinosaur-dominated Mesozoic floodplain communities.",
    url = "https://doi.org/10.1130/g47399.1",
    doi = "10.1130/g47399.1",
    openalex = "W3011136744",
    references = "doi101007b110345, doi101016003101828790040x, doi101016jepsl200407015, doi101016jpalaeo201206027, doi101016s0016703796002402, doi101038s41598019517095, doi101073pnas1004933107, doi101073pnas1521478113, doi101098rsos161086, doi101186147267851314, doi101186s1289801601068, doi101371journalpone0012292, doi1016660094837336180, doi1018901540929520075429anfie20co2, doi102475ajs3047612"
}

Spinosaurids are among the most distinctive and yet poorly-known of large-bodied theropod dinosaurs, a situation exacerbated by their mostly fragmentary fossil record and competing views regarding their palaeobiology. Here, we report two new Early Cretaceous spinosaurid specimens from the Wessex Formation (Barremian) of the Isle of Wight. Large-scale phylogenetic analyses using parsimony and Bayesian techniques recover the pair in a new clade within Baryonychinae that also includes the hypodigm of the African spinosaurid Suchomimus. Both specimens represent distinct and novel taxa, herein named Ceratosuchops inferodios gen. et sp. nov. and Riparovenator milnerae gen. et sp. nov. A palaeogeographic reconstruction suggests a European origin for Spinosauridae, with at least two dispersal events into Africa. These new finds provide welcome information on poorly sampled areas of spinosaurid anatomy, suggest that sympatry was present and potentially common in baryonychines and spinosaurids as a whole, and contribute to updated palaeobiogeographic reconstructions for the clade.

@article{doi101038s41598021978708,
    author = "Barker, Chris T. and Hone, David W. E. and Naish, Darren and Cau, Andrea and Lockwood, Jeremy A. F. and Foster, Brian and Clarkin, Claire and Schneider, Philipp and Gostling, Neil J.",
    title = "New spinosaurids from the Wessex Formation (Early Cretaceous, UK) and the European origins of Spinosauridae",
    year = "2021",
    journal = "Scientific Reports",
    abstract = "Spinosaurids are among the most distinctive and yet poorly-known of large-bodied theropod dinosaurs, a situation exacerbated by their mostly fragmentary fossil record and competing views regarding their palaeobiology. Here, we report two new Early Cretaceous spinosaurid specimens from the Wessex Formation (Barremian) of the Isle of Wight. Large-scale phylogenetic analyses using parsimony and Bayesian techniques recover the pair in a new clade within Baryonychinae that also includes the hypodigm of the African spinosaurid Suchomimus. Both specimens represent distinct and novel taxa, herein named Ceratosuchops inferodios gen. et sp. nov. and Riparovenator milnerae gen. et sp. nov. A palaeogeographic reconstruction suggests a European origin for Spinosauridae, with at least two dispersal events into Africa. These new finds provide welcome information on poorly sampled areas of spinosaurid anatomy, suggest that sympatry was present and potentially common in baryonychines and spinosaurids as a whole, and contribute to updated palaeobiogeographic reconstructions for the clade.",
    url = "https://doi.org/10.1038/s41598-021-97870-8",
    doi = "10.1038/s41598-021-97870-8",
    openalex = "W3203271713",
    references = "doi101016jcretres201103005, doi101038s4159802066261w, doi101073pnas1613813113, doi1010800272463420201877151, doi101111brv12666, doi104202app20110144, doi107717peerj5976, doi107717peerj9192, sánchezhernández2007dinosaurs"
}

We describe a new species of the albanerpetontid amphibian Albanerpeton from three localities in the Lower Cretaceous Cloverly Formation of Wyoming, U.S.A. Radiometric dates between ∼111–112 Ma indicate it is slightly younger than A. arthridion from the Antlers Formation. The new species is diagnosed on a pair of fused frontals that possess a unique combination of characters, mixing plesiomorphic features of the internasal process with a more derived overall shape and proportions. Referred material includes premaxillae, maxillae, dentaries, atlantes, ‘axes,’ trunk vertebrae, humeri, and an ilium.Phylogenetic analyses place the new species near the base of Albanerpeton sensu lato but without fully resolving its position. The inclusion of Shirerpeton and Wesserpeton within this clade opens up the possibility that these genera might be incorporated into Albanerpeton, or that a number of species formerly assigned to Albanerpeton might receive new generic assignments. By including several informal species in our analysis, it becomes clear that character distributions are more homoplastic and that past genus typologies are probably less secure. We assign the new species to Albanerpeton conservatively, pending further phylogenetic study.The Cloverly Albanerpeton is found in unambiguously aquatic deposits, suggesting that the animal lived near these settings for at least part of its life. This is a common habitat for Mesozoic albanerpetontids, unlike the karst-dominated, often drier, deposits in which Cenozoic species are typically found. Despite the recent discovery of a probable arboreal species, it is likely that albanerpetontids inhabited a range of habitats throughout their evolutionary history.

@article{doi1010800272463420212003372,
    author = "Carrano, Matthew T. and Oreska, Matthew P. J. and Murch, Abree and Trujillo, Kelli C. and Chamberlain, Kevin R.",
    title = "Vertebrate paleontology of the Cloverly Formation (Lower Cretaceous), III: a new species of Albanerpeton, with biogeographic and paleoecological implications",
    year = "2021",
    journal = "Journal of Vertebrate Paleontology",
    abstract = "We describe a new species of the albanerpetontid amphibian Albanerpeton from three localities in the Lower Cretaceous Cloverly Formation of Wyoming, U.S.A. Radiometric dates between ∼111–112 Ma indicate it is slightly younger than A. arthridion from the Antlers Formation. The new species is diagnosed on a pair of fused frontals that possess a unique combination of characters, mixing plesiomorphic features of the internasal process with a more derived overall shape and proportions. Referred material includes premaxillae, maxillae, dentaries, atlantes, ‘axes,’ trunk vertebrae, humeri, and an ilium.Phylogenetic analyses place the new species near the base of Albanerpeton sensu lato but without fully resolving its position. The inclusion of Shirerpeton and Wesserpeton within this clade opens up the possibility that these genera might be incorporated into Albanerpeton, or that a number of species formerly assigned to Albanerpeton might receive new generic assignments. By including several informal species in our analysis, it becomes clear that character distributions are more homoplastic and that past genus typologies are probably less secure. We assign the new species to Albanerpeton conservatively, pending further phylogenetic study.The Cloverly Albanerpeton is found in unambiguously aquatic deposits, suggesting that the animal lived near these settings for at least part of its life. This is a common habitat for Mesozoic albanerpetontids, unlike the karst-dominated, often drier, deposits in which Cenozoic species are typically found. Despite the recent discovery of a probable arboreal species, it is likely that albanerpetontids inhabited a range of habitats throughout their evolutionary history.",
    url = "https://doi.org/10.1080/02724634.2021.2003372",
    doi = "10.1080/02724634.2021.2003372",
    openalex = "W4214830085",
    references = "carrano2016vertebrate, doi101016jgr201412004, doi101016jtecto201204021, doi101016s0031018203003675, doi10108002724634198210011915, doi101080027246342012717567, doi10108008120090500100077, doi101111cla12160, doi101111j10960031200800217x, doi101126scienceabb6005, doi101371journalpone0189767, doi1016660094837336180, doi1023071933240, doi105860choice325663, doi105860choice461500"
}

Well-sampled dinosaur communities from the Jurassic through the early Late Cretaceous show greater taxonomic diversity among larger (>50 kg) theropod taxa than communities of the Campano-Maastrichtian, particularly to those of eastern/central Asia and Laramidia. The large carnivore guilds in Asiamerican assemblages are monopolized by tyrannosaurids, with adult medium-sized (50–500 kg) predators rare or absent. In contrast, various clades of theropods are found to occupy these body sizes in earlier faunas, including early tyrannosauroids. Assemblages with “missing middle-sized” predators are not found to have correspondingly sparser diversity of potential prey species recorded in these same faunas. The “missing middle-sized” niches in the theropod guilds of Late Cretaceous Laramidia and Asia may have been assimilated by juvenile and subadults of tyrannosaurid species, functionally distinct from their adult ecomorphologies. It is speculated that if tyrannosaurids assimilated the niches previously occupied by mid-sized theropod predators, we would expect the evolution of distinct transitions in morphology and possibly the delay of the achievement of somatic maturity in species of this taxon.

@article{doi101139cjes20200174,
    author = "Holtz, Thomas R.",
    title = "Theropod guild structure and the tyrannosaurid niche assimilation hypothesis: implications for predatory dinosaur macroecology and ontogeny in later Late Cretaceous Asiamerica 1",
    year = "2021",
    journal = "Canadian Journal of Earth Sciences",
    abstract = "Well-sampled dinosaur communities from the Jurassic through the early Late Cretaceous show greater taxonomic diversity among larger (>50 kg) theropod taxa than communities of the Campano-Maastrichtian, particularly to those of eastern/central Asia and Laramidia. The large carnivore guilds in Asiamerican assemblages are monopolized by tyrannosaurids, with adult medium-sized (50–500 kg) predators rare or absent. In contrast, various clades of theropods are found to occupy these body sizes in earlier faunas, including early tyrannosauroids. Assemblages with “missing middle-sized” predators are not found to have correspondingly sparser diversity of potential prey species recorded in these same faunas. The “missing middle-sized” niches in the theropod guilds of Late Cretaceous Laramidia and Asia may have been assimilated by juvenile and subadults of tyrannosaurid species, functionally distinct from their adult ecomorphologies. It is speculated that if tyrannosaurids assimilated the niches previously occupied by mid-sized theropod predators, we would expect the evolution of distinct transitions in morphology and possibly the delay of the achievement of somatic maturity in species of this taxon.",
    url = "https://doi.org/10.1139/cjes-2020-0174",
    doi = "10.1139/cjes-2020-0174",
    openalex = "W3168560974",
    references = "doi101016jcub201803042, doi101017pab201519, doi101017s0094837300011891, doi10103846266, doi101038nature02699, doi101038ncomms3827, doi101038s4155901908880, doi101038s41598019517095, doi101038srep20252, doi101073pnas1600140113, doi101093nsrnwu055, doi101098rspb20202258, doi101111brv12638, doi101111j1469185x201000137x, doi101111j15023931200900187x, doi101126sciadvaax6250, doi101126science1065522, doi101126science1161833, doi101126science28454232137, doi101139cjes20120185, doi101139cjes20170031, doi101139cjes20190019, doi101371journalpone0054329, doi101371journalpone0188426, doi1017161paleo180818764, doi1023071942327, doi1023072411924, doi1029920070860302, doi103897zookeys92847517, doi107717peerj9192, openalexw2183707334, openalexw2971401580"
}

@inproceedings{andbeatty2022megaflora,
    author = "Beatty, William and Ruhland, Nicole E. and Davitt, Sophia E. and Khatri, Samantha I. and Schroeder, Adam J.",
    title = "MEGAFLORA FOSSILS FROM A DINOSAUR EXCAVATION SITE IN THE LATE CRETACEOUS HELL CREEK FORMATION OF WESTERN NORTH DAKOTA",
    year = "2022",
    booktitle = "Geological Society of America Abstracts with Programs",
    url = "https://doi.org/10.1130/abs/2022am-383445",
    doi = "10.1130/abs/2022am-383445",
    openalex = "W4313135711"
}

Abstract The Late Cretaceous dinosaur Tyrannosaurus rex was recently split into three species based on the premise that variation in the T. rex hypodigm is exceptional, indicating cryptic species and “robust” and “gracile” morphs. The morphs are based on proportional ratios throughout the skeleton. The species are claimed to be stratigraphically separate, with an early robust species followed by robust and gracile descendants. There are problems with the hypothesis: the taxon diagnoses are based on two features that overlap between the species; several skulls cannot be identified based on the diagnoses; proportional comparisons between Tyrannosaurus and other theropods are based on incomparable samples; the tooth data are problematic; the stratigraphic framework divides the Hell Creek Formation into thirds, without the stratigraphic position of each specimen, or independent age control showing the subdivisions are coeval over the entire geographic area; previous work found variation in T. rex, but it cannot be parsed into discrete categories. We tested for “gracile” and “robust” morphs by analyzing the femoral and tooth ratios that were published in the multiple species study using agglomerative hierarchical clustering. The results found that each set of ratios are explained by one cluster, showing that dimorphism is not supported. We tested for exceptional variation of the femoral ratio of Tyrannosaurus; we calculated the mean intraspecific robusticity for 112 species of living birds and 4 nonavian theropods. The results showed that the absolute variation in Tyrannosaurus is unexceptional and it does not indicate cryptic diversity. We conclude that “ T. regina ” and “ T. imperator ” are subjective junior synonyms of T. rex.

@article{doi101007s11692022095731,
    author = "Carr, Thomas D. and Napoli, James G. and Brusatte, Stephen L. and Holtz, Thomas R. and Hone, David W. E. and Williamson, Thomas E. and Zanno, Lindsay E.",
    title = "Insufficient Evidence for Multiple Species of Tyrannosaurus in the Latest Cretaceous of North America: A Comment on “The Tyrant Lizard King, Queen and Emperor: Multiple Lines of Morphological and Stratigraphic Evidence Support Subtle Evolution and Probable Speciation Within the North American Genus Tyrannosaurus”",
    year = "2022",
    journal = "Evolutionary Biology",
    abstract = "Abstract The Late Cretaceous dinosaur Tyrannosaurus rex was recently split into three species based on the premise that variation in the T. rex hypodigm is exceptional, indicating cryptic species and “robust” and “gracile” morphs. The morphs are based on proportional ratios throughout the skeleton. The species are claimed to be stratigraphically separate, with an early robust species followed by robust and gracile descendants. There are problems with the hypothesis: the taxon diagnoses are based on two features that overlap between the species; several skulls cannot be identified based on the diagnoses; proportional comparisons between Tyrannosaurus and other theropods are based on incomparable samples; the tooth data are problematic; the stratigraphic framework divides the Hell Creek Formation into thirds, without the stratigraphic position of each specimen, or independent age control showing the subdivisions are coeval over the entire geographic area; previous work found variation in T. rex, but it cannot be parsed into discrete categories. We tested for “gracile” and “robust” morphs by analyzing the femoral and tooth ratios that were published in the multiple species study using agglomerative hierarchical clustering. The results found that each set of ratios are explained by one cluster, showing that dimorphism is not supported. We tested for exceptional variation of the femoral ratio of Tyrannosaurus; we calculated the mean intraspecific robusticity for 112 species of living birds and 4 nonavian theropods. The results showed that the absolute variation in Tyrannosaurus is unexceptional and it does not indicate cryptic diversity. We conclude that “ T. regina ” and “ T. imperator ” are subjective junior synonyms of T. rex.",
    url = "https://doi.org/10.1007/s11692-022-09573-1",
    doi = "10.1007/s11692-022-09573-1",
    openalex = "W4287510523",
    references = "doi101038114085a0, doi10108010635150590906037, doi101093biolinneanblaa105, doi101126science2562999, doi101139cjes20170031, doi101139cjes20200145, doi101139e78109, doi101371journalpone0082000, doi1015468yhxmzl, doi102110palo2003p0322, doi1023072412740, doi1023073889334, doi105281zenodo814935, doi105860choice393984, doi105860choice434677, doi105860choice435902"
}

A new spinosaurid genus and species is described based on the right maxilla and five caudal vertebrae of a single specimen from the Arcillas de Morella Formation (Early Cretaceous) at the locality of Cinctorres (Castellón, Spain). Protathlitis cinctorrensis gen. et sp. nov. is diagnosed by one autapomorphic feature as well as by a unique combination of characters. The autapomorphy includes a subcircular depression in the anterior corner of the antorbital fossa in the maxilla. The new Iberian species is recovered as a basal baryonychine. The recognition of Protathlitis cinctorrensis gen. et sp. nov. as the first baryonychine dinosaur species identified from the Arcillas de Morella Formation (late Barremian) from the same time as Vallibonavenatrix cani, the first spinosaurine dinosaur from the same formation in the Morella subbasin (Maestrat Basin, eastern Spain), indicates that the Iberian Peninsula was home to a highly diverse assemblage of medium-to-large bodied spinosaurid dinosaurs. It seems that spinosaurids appeared during the Early Cretaceous in Laurasia, with the two subfamilies occupying the western part of Europe during this period. Later, during the Barremian-Aptian, they migrated to Africa and Asia, where they would diversify. In Europe, baryonychines were dominant, while in Africa, spinosaurines were most abundant.

@article{doi101038s41598023334182,
    author = "Cubedo, Andrés Santos and de Santisteban, Carlos and Poza, Begoña and Meseguer, Sergi",
    title = "A new spinosaurid dinosaur species from the Early Cretaceous of Cinctorres (Spain)",
    year = "2023",
    journal = "Scientific Reports",
    abstract = "A new spinosaurid genus and species is described based on the right maxilla and five caudal vertebrae of a single specimen from the Arcillas de Morella Formation (Early Cretaceous) at the locality of Cinctorres (Castellón, Spain). Protathlitis cinctorrensis gen. et sp. nov. is diagnosed by one autapomorphic feature as well as by a unique combination of characters. The autapomorphy includes a subcircular depression in the anterior corner of the antorbital fossa in the maxilla. The new Iberian species is recovered as a basal baryonychine. The recognition of Protathlitis cinctorrensis gen. et sp. nov. as the first baryonychine dinosaur species identified from the Arcillas de Morella Formation (late Barremian) from the same time as Vallibonavenatrix cani, the first spinosaurine dinosaur from the same formation in the Morella subbasin (Maestrat Basin, eastern Spain), indicates that the Iberian Peninsula was home to a highly diverse assemblage of medium-to-large bodied spinosaurid dinosaurs. It seems that spinosaurids appeared during the Early Cretaceous in Laurasia, with the two subfamilies occupying the western part of Europe during this period. Later, during the Barremian-Aptian, they migrated to Africa and Asia, where they would diversify. In Europe, baryonychines were dominant, while in Africa, spinosaurines were most abundant.",
    url = "https://doi.org/10.1038/s41598-023-33418-2",
    doi = "10.1038/s41598-023-33418-2",
    openalex = "W4377092856",
    references = "doi103897zookeys92847517, sánchezhernández2007dinosaurs"
}