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New specimens from the Bridger Formation allow for a critical review of the alpha taxonomy and evolution of the two most abundant species of sciuravid rodents from the Early Eocene of the Green River Basin, Sciuravus nitidus and S. undans. Previously, the two species were considered to be synonymous, based on studies of the upper and/or lower dentitions. Specimens with nearly complete lower dentitions are studied for the first time and they reveal clear distinctions between the two species in the molar crown patterns, incisor shape, and mandible morphology. The key specimen, UM 101638, closely matched the type specimen of S. undans, YPM 13349, in molar dimensions and morphology for m1-2.


Dr. Deborah Anderson, Biology

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biology, taxonomy, sciuravid rodents

A Taxonomic Revision and Characterization of Sciuravus nitidus and S. undans (Rodentia; Sciuravidae), early to middle Eocene Rodents from the Bridger Formation, Green River Basin, Wyoming

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