18 research outputs found

    Diverse New Microvertebrate Assemblage from the Upper Triassic Cumnock Formation, Sanford Subbasin, North Carolina, USA

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    The Moncure microvertebrate locality in the Cumnock Formation, Sanford sub-basin, North Carolina, dramatically increases the known Late Triassic age vertebrate assemblage from the Deep River Basin. The 50,000 recovered microvertebrate fossils include osteichthyans, amphibians, and numerous lepidosauromorph, archosauriform, and synapsid amniotes. Actinopterygian fossils consist of thousands of scales, teeth, skull, and lower jaw fragments, principally of redfieldiids and semionotids. Non-tetrapod sarcopterygians include the dipnoan Arganodus sp., the first record of lungfish in the Newark Supergroup. Temnospondyls are comparatively rare but the preserved centra, teeth, and skull fragments probably represent small (juvenile) metoposaurids. Two fragmentary teeth are assigned to the unusual reptile Colognathus obscurus (Case). Poorly preserved but intriguing records include acrodont and pleurodont jaw fragments tentatively assigned to lepidosaurs. Among the archosauriform teeth is a taxon distinct from R. callenderi that we assign to Revueltosaurus olseni new combination, a morphotype best assigned to cf. Galtonia, the first Newark Supergroup record of Crosbysaurus sp., and several other archosauriform tooth morphotypes, as well as grooved teeth assigned to the recently named species Uatchitodon schneideri. Synapsids represented by molariform teeth include both "traversodontids" assigned to aff. Boreogomphodon and the "dromatheriid" Microconodon. These records are biogeographically important, with many new records for the Cumnock Formation and/or the Newark Supergroup. In particular, Colognathus, Crosbysaurus, and Uatchitodon are known from basins of Adamanian age in the southwestern U.S.A. These new records include microvertebrate taxa more typical of non-Newark basins (abundant archosauriforms, temnospondyls, lungfish) as well as more typical Newark osteichthyans and synapsid-rich faunal elements

    Small Theropod Teeth from the Late Cretaceous of the San Juan Basin, Northwestern New Mexico and Their Implications for Understanding Latest Cretaceous Dinosaur Evolution

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    Studying the evolution and biogeographic distribution of dinosaurs during the latest Cretaceous is critical for better understanding the end-Cretaceous extinction event that killed off all non-avian dinosaurs. Western North America contains among the best records of Late Cretaceous terrestrial vertebrates in the world, but is biased against small-bodied dinosaurs. Isolated teeth are the primary evidence for understanding the diversity and evolution of small-bodied theropod dinosaurs during the Late Cretaceous, but few such specimens have been well documented from outside of the northern Rockies, making it difficult to assess Late Cretaceous dinosaur diversity and biogeographic patterns. We describe small theropod teeth from the San Juan Basin of northwestern New Mexico. These specimens were collected from strata spanning Santonian - Maastrichtian. We grouped isolated theropod teeth into several morphotypes, which we assigned to higher-level theropod clades based on possession of phylogenetic synapomorphies. We then used principal components analysis and discriminant function analyses to gauge whether the San Juan Basin teeth overlap with, or are quantitatively distinct from, similar tooth morphotypes from other geographic areas. The San Juan Basin contains a diverse record of small theropods. Late Campanian assemblages differ from approximately coeval assemblages of the northern Rockies in being less diverse with only rare representatives of troodontids and a Dromaeosaurus-like taxon. We also provide evidence that erect and recurved morphs of a Richardoestesia-like taxon represent a single heterodont species. A late Maastrichtian assemblage is dominated by a distinct troodontid. The differences between northern and southern faunas based on isolated theropod teeth provide evidence for provinciality in the late Campanian and the late Maastrichtian of North America. However, there is no indication that major components of small-bodied theropod diversity were lost during the Maastrichtian in New Mexico. The same pattern seen in northern faunas, which may provide evidence for an abrupt dinosaur extinction

    Investigations on canadian dinosaurs

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    The present study detects changes in dinosaur assemblages from the Upper Creataceous of South Alberta, Canada, by analyzing isolated dinosaur teeth from vertebrate microfossil sites. The studied formations, namely the coastal Milk River, Oldman, Dinosaur Park, Horseshoe Canyon and the inland Scollard Formations represent a time span of approximately twenty million years. In the Latest Maastrichtian, the inland Scollard Formation and the coastal Lance and Frenchman Formations are examined in order to obtain a certain geographical range and a comparison of inland versus coastal environments. Two distinct assemblages, which differ in the relative abundance of taxa, are present during the time span of this study: assemblage A is present in the Early Campanian Milk River Formation, assemblage B takes over in the Campanian Oldman, Dinosaur Park and Horseshoe Canyon Formations and is replaced by assemblage A again in the Latest Maastrichtian Scollard, Lance and Frenchman Formations. Thus, assemblage A might have migrated to areas with more appropriate ecological conditions during the Campanian. The time for which assemblage A persisted is therefore estimated to about twenty (or more) million years. The relative dating of biostratigraphic zones is put into question by these results, since palaeo-assemblages persist for very long time spans and rather hint to environmental controls than to the time in which they lived. The diversity of dinosaur taxa does not decline in the stratigraphically uppermost locality which is situated 13 m below the K/T-boundary. This hints towards stability of the ecosystem up to this time. By putting together taxa to ecological guilds, it is attempted to identify ecological controls that are responsible for the observed change of assemblages. As a result, neither 'proximity to coast' nor 'humidity' are primary factors for this change. Although more studies of this kind would be necessary on larger geographical and stratigraphical ranges, data of this study hint to the following vegetational structure of the palaeo-environment: the Milk River Formation was covered with dense vegetation and the Oldman Formation was relatively open in vegetational structure and these conditions persisted during the following Dinosaur Park Group. The Horseshoe Canyon Formation seems to be covered with dense vegetation again and the environment opens in the inland Scollard Formation. A rough investigation of the carnivore/herbivore ratio within the Dinosauria shows that the predators from the Latest Maastrichtian fed on relatively more non-dinosaurs than in earlier times. Finally, the use of neo-ecological concepts in palaeo-ecology is discussed. (orig.)Available from TIB Hannover: RN 5205(196) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

    Late Maastrichtian small-sized herpetofauna from Valencia province, eastern Spain

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    This is an Accepted Manuscript of an article published by Taylor & Francis in Historical Biology on 2017, available online: http://www.tandfonline.com/10.1080/08912963.2015.1122004[EN] A Late Maastrichtian microvertebrate assemblage which includes amphibian remains was recovered from continental deposits of the palaeontological site of La Solana, Valencia Province, Spain. This site is composed of variegated mudstones, pedogenically modified, interbedded with fluvial sand bodies and freshwater limestones lenses, and has also yielded plant debris, freshwater and oligohaline invertebrates, abundant fish remains (isolated bones and scales), turtle plates and archosaur bones. This fossil assemblage, dominated by aquatic forms, also includes semiaquatic and terrestrial elements, and may be interpreted as the palaeofauna of a wetland environment with terrestrial environs. The new material described here consists of fragmentary remains of an indeterminate albanerpetontid, a salamandrid and two anuran taxa (an alytid and a palaeobatrachid). The amphibians from La Solana are typical Laurasiatic taxa. This faunal association shows broad similarities to other coeval faunas of the Iberian Peninsula and contrasts with the Upper Campanian¿Lower Maastrichtian sites where Gondwanan elements are frequent.This work was supported by the Hungarian Scientific Research Fund [grant number OTKA NF 84193]; the Spanish Ministry of Economy and Competitiveness (MINECO) [project numbers CGL2013-47521-P and CGL2014-535484].Szentesi, Z.; Company Rodríguez, J. (2017). Late Maastrichtian small-sized herpetofauna from Valencia province, eastern Spain. Historical Biology (Online). 29(1):43-52. https://doi.org/10.1080/08912963.2015.11220044352291Astibia, H., Buffetaut, E., Buscalioni, A. D., Cappetta, H., Corral, C., Estes, R., … Tong, H. (1990). 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    First evidence of ankylosaurian dinosaurs (Ornithischia: Thyreophora) from the mid-Cretaceous (late Albian-Cenomanian) Winton Formation of Queensland, Australia

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    First evidence of ankylosaurian dinosaurs (Ornithischia: Thyreophora) from the mid-Cretaceous (late Albian-Cenomanian) Winton Formation of Queensland, Australia. Alcheringa 37, 261-269. ISSN 0311-5518. The first evidence of ankylosaurian thyreophorans from the Winton Formation (late Albian-Cenomanian) of central-western Queensland, Australia, reveals new information about the temporal and palaeobiogeographical range of these dinosaurs within Gondwana. The material, which comprises isolated teeth, is the youngest evidence of ankylosaurs in Australia. Although the Winton teeth exhibit a suite of pleisiomorphic characteristics that are also seen in other Australian and Gondwanan ankylosaur taxa, they are morphologically distinct and very likely represent a new taxon. Their discovery adds to the growing body of evidence indicating that thyreophorans, and in particular ankylosaurians, constitute a diverse and important component of Australia's mid-Cretaceous dinosaur fauna
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