Abstract

Several taxa of supposed "Kimballian" (late Tertiary) rodents collected from Uptegrove Quarry in western Nebraska are shown to be based on remains of modern species apparently introduced into the fossil assemblage by burrowing. Citellus kimballensis Kent, 1967, is synonymous with Spermophilus richardsoni, a modern Richardson's ground squirrel, and Propliophenacomys uptegrovensis Martin, 1975, is based on a partial skull of the Recent heather vole, Phenacomys intermedius. Recent species of Thomomys and Perognathus are also present in the Uptegrove assemblage and their remains are, likewise, unmineralized and "fresh" in appearance, unlike the genuine fossil ungulate and carnivore remains from the same quarry. The latter fossils, especially the horse Nannippus lenticularis, indicate that the Uptegrove Local Fauna is late Hemphillian in age.--Modified journal abstracts.

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