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

Todd D. Cook, Michael G. Newbrey, Donald B. Brinkman, James I. Kirkland

Research output: Chapter in Book/Report/Conference proceedingChapter

13 Scopus citations


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 My ledaphus 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.

Original languageEnglish (US)
Title of host publicationThrough the End of the Cretaceous in the Type Locality of the Hell Creek Formation in Montana and Adjacent Areas
EditorsGregory Wilson, William Clemens, John Horner, Joseph Hartman
Number of pages18
StatePublished - Feb 26 2014

Publication series

NameSpecial Paper of the Geological Society of America
ISSN (Print)0072-1077

All Science Journal Classification (ASJC) codes

  • Geology


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