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Euselachians from the freshwater deposits of the Hell Creek Formation of Montana

By
Todd D. Cook
Todd D. Cook
Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada
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Michael G. Newbrey
Michael G. Newbrey
Royal Tyrrell Museum of Palaeontology, Drumheller, Alberta T0J 0Y0, Canada, and Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada
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Donald B. Brinkman
Donald B. Brinkman
Royal Tyrrell Museum of Palaeontology, Drumheller, Alberta T0J 0Y0, Canada
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James I. Kirkland
James I. Kirkland
Ground Water and Paleontology, Utah Geological Survey, P.O. Box 146100, 1594 West North Temple, Suite 3110, Salt Lake City, Utah 84114, USA
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Published:
January 01, 2014

An examination of freshwater euselachian fossils from the Maastrichtian lower and upper Hell Creek Formation, and the Bug Creek Anthills (Cretaceous-Paleogene boundary), and the early Paleocene (Puercan) Tullock Member of the Fort Union Formation of Montana, USA, revealed seven taxa: Lonchidion selachos, Protoginglymostoma estesi, Chiloscyllium, Restesia americana, Ischyrhiza avonicola, Myledaphus pustulosus n. sp., and Dasyatis (Dasyatidae). Squatirhina americana is redescribed to the new genus Restesia based on unique crown morphology. Dasyatis is only reported from the Paleocene. This is in contrast to the other collected taxa, which are only known from the Cretaceous. Ischyrhiza is not reported in our samples from the Hell Creek Formation despite earlier erroneous claims; however, the taxon is present in a sample from the Bug Creek Anthills. We suggest that this taxon infrequently moved into the freshwater rivers to forage. Lonchidion selachos occurs only in the upper Hell Creek Formation, and we hypothesize that the upper Hell Creek localities were deposited during a warm interval, as the paleodistribution of L. selachos shifted significantly to the north during warmer periods in the Santonian and Campanian. Of the taxa found in the Hell Creek Formation and the Bug Creek Anthills, only Myledaphus is found in Paleogene deposits; however, specimens are extremely rare. The occurrence of Myledaphus in the Paleogene is suggested to be due to the occurrence of reworked material.

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GSA Special Papers

Through the End of the Cretaceous in the Type Locality of the Hell Creek Formation in Montana and Adjacent Areas

Gregory P. Wilson
Gregory P. Wilson
Department of Biology and Burke Museum of Natural History and Culture, University of Washington, Seattle, Washington 98195-1800, USA
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William A. Clemens
William A. Clemens
Museum of Paleontology, University of California, Berkeley, Berkeley, California 94720-4780, USA
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John R. Horner
John R. Horner
Museum of the Rockies, Montana State University, Bozeman, Montana 59717-0040, USA
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Joseph H. Hartman
Joseph H. Hartman
Harold Hamm School of Geology and Geological Engineering, University of North Dakota, Grand Forks, North Dakota 58202-8358, USA
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Geological Society of America
Volume
503
ISBN print:
9780813725031
Publication date:
January 01, 2014

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