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Earliest Eocene Miacidae (Mammalia: Carnivora) from northwestern Wyoming

  • Ronald E. Heinrich (a1), Suzanne G. Strait (a2) and Peter Houde (a3)

Fossil carnivorans are described from earliest Eocene localities in the Clarks Fork and southern Bighorn basins of Wyoming. Three new species, Miacis rosei, Uintacyon gingerichi, and Vassacyon bowni, collected from the base of the Wasatchian North American Land Mammal Age (Wa-0), are the smallest and possibly most basal members of their respective genera, and increase from one to four the number of miacids known from this faunal zone. An upper dentition of Miacis deutschi from slightly younger (Wa-2) deposits is also described. Previously known only from lower teeth and a single M1, the specimen of M. deutschi includes the left P3-M2, alveoli for the canine, first two premolars and the last molar, as well as most of the maxilla. the new material helps fill gaps in our knowledge of the dental morphology of basal Miacidae and provides insight into the functional differences of the carnassial teeth in the diverging Uintacyon and Miacis lineages. It also provides an opportunity to further assess the hypothesis that climactic warming in the earliest Eocene resulted in evolutionary dwarfing of mammalian species; based on three criteria for identifying dwarfed species at least one of the new taxa, U. gingerichi, is consistent with this hypothesis.

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D. J. Froehlich 2002. Quo vadis eohippus? The systematics and taxonomy of the early Eocene equids (Perissodactyla). Zoological Journal of the Linnean Society, 134(2): 141256.

P. D. Gingerich 2003. Mammalian responses to climate change at the Paleocene-Eocene boundary: Polecat Bench record in the northern Bighorn Basin, Wyoming, p. 463478. In S. L. Wing , P. D. Gingerich , and E. Thomas (eds.), Causes and Consequences of Globally Warm Climates in the Early Paleogene. Geological Society of America Special Paper 369.

C. Stock 1934. New Creodonta from the Sespe Upper Eocene, California. Proceedings of the National Academy of Sciences, 20:423427.

G. D. Wesley and J. J. Flynn 2005. Phylogeny of the Carnivora: Basal relationships among the carnivoramorphans, and assessment of the position of “Miacoidea” relative to crown-clade Carnivora. Journal of Systematic Palaeontology, 3(1): 128.

J. Yans , S. G. Strait , T. Smith , C. Dupuis , E. Steurbaut , and P. D. Gingerich 2006. High resolution carbon isotope stratigraphy and mammalian faunal change at the Paleocene-Eocene boundary in the honeycombs area of the southern Bighorn Basin, Wyoming. American Journal of Science, 306:712735.

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Journal of Paleontology
  • ISSN: 0022-3360
  • EISSN: 1937-2337
  • URL: /core/journals/journal-of-paleontology
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