Taphonomy of large marine vertebrates in the Upper Cretaceous (Cenomanian-Turonian) Tropic Shale of southern Utah |
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| Institution: | 1. Department of Geology, St. Norbert College, 100 Grant Street, De Pere, WI 54115, USA;2. Department of Geology, Museum of Northern Arizona, 3101 North Fort Valley Road, Flagstaff, AZ 86001, USA;1. Florida Museum of Natural History, University of Florida, 1659 Museum Road, PO Box 117800, Gainesville FL 32611, USA;2. Geological-Paleontological Department, Natural History Museum Vienna, Burgring 7, 1010 Vienna, Austria;3. Department of Geology and Paleontology, Faculty of Natural Sciences, Comenius University, Mlynská dolina G1, 842 15 Bratislava, Slovakia;4. Natural History Museum of Denmark, Geological Museum, University of Copenhagen, Øster Voldgade 5-7, 1350 Copenhagen K, Denmark;1. ITT Fossil, Instituto Tecnológico de Micropaleontologia, Universidade do Vale do Rio dos Sinos (UNISINOS), Av. UNISINOS, 950, B. Cristo Rei/CEP: 93.022-000, São Leopoldo, RS, Brazil;2. Instituto Antártico Argentino (IAA), Buenos Aires, Argentina;3. IDEAN-CONICET, Departamento de Ciências Geológicas, Universidad de Buenos Aires, Pabellón II, Ciudad Universitaria, 1428, Buenos Aires, Argentina;4. Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT, UK;5. Museu Nacional – Universidade Federal do Rio de Janeiro, Brazil;1. Universidade do Estado do Rio de Janeiro, Departamento de Zoologia, IBRAG, Rua São Francisco Xavier, 524, 20559-900 Rio de Janeiro, Brazil;2. Museu de Paleontologia de Marília, Prefeitura Municipal de Marília, Av. Sampaio Vidal, 245, 17500-020 Marília, São Paulo, Brazil;3. Centro de Pesquisas Paleontológicas Llewellyn Ivor Price, Complexo Cultural e Cientí?co Peirópolis (CCCP/UFTM), BR-262, Km 784, Bairro Peirópolis, Uberaba, Minas Gerais, Brazil;4. Departamento de Paleontologia e Estratigrafia, UFRGS, Av. Bento Gonçalves, 9500, Agronomia, 91540-000, Porto Alegre, RS, Brazil;2. Oertijdmuseum, Bosscheweg 80, 5283 WB Boxtel, The Netherlands;3. Área de Paleontología, Departamento de Ciencias de la Tierra, Universidad de Zaragoza, Zaragoza, Spain;4. Instituto de Geología, Universidad Nacional Autónoma de México, Ciudad Universitaria, Coyoacán, Ciudad de México 04510, Mexico;1. Department of Geology, Naturalis Biodiversity Center, Postbus 9517, 2300 RA Leiden, The Netherlands;2. Jurassic Jim, 22 High Street, Shanklin, Isle of Wight PO37 6JY, UK;1. Departamento de Geologia, Centro de Tecnologia e Geociências, Universidade Federal de Pernambuco, Brazil;2. Setor de Paleontologia, Museu de História Natural, Universidade Federal de Alagoas, Brazil |
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| Abstract: | Sediments from the Upper Cretaceous (Cenomanian-Turonian) Tropic Shale were deposited along the western margin of the Western Interior Seaway, in present-day southern Utah. Marine vertebrates from this formation include plesiosaurs, mosasaurs, bony fish, sharks, and turtles. They are concentrated in the lower portion of the Tropic Shale, mostly between Bentonites B and D. Study of the taphonomic condition of these vertebrates has contributed to an understanding of how they were preserved as well as a detailed paleoenvironment for the Tropic Shale. Physical factors played the dominant role in their preservation, with robust and durable skeletal elements, such as teeth and vertebrae, being most common within the shale. Isolated bones and teeth are also relatively common within the formation, while complete and nearly complete skeletons are more rare. Biological factors played a less dominant role, with no evidence of epifaunal or infaunal activity preserved with any of the skeletal remains. In addition, scavenging marks (both bite and gnaw marks) are relatively uncommon, typically only being found on more complete specimens. A signature of post-burial alteration can be recognized as low levels of abrasion, weathering, and compression and high levels of fracturing of vertebrate skeletal material. Slightly higher levels of abrasion and weathering occur to the west, closer to the ancient shoreline, suggesting some pre-burial alteration. The preservation of marine vertebrates in the Tropic Shale suggests a low energy marine environment with some weak bottom currents and low levels of benthic oxygen. The substrate ranged from soft and soupy to firm, with moderate sedimentation rates resulting in relatively rapid burial. |
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| Keywords: | Tropic Shale Utah Western Interior Seaway Taphonomy Paleoenvironment Plesiosaur |
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