New species of cricetid rodents (Mammalia) from the late Miocene (Hemphillian) previously referred to Peromyscus pliocenicus Wilson

摘要

Specimens previously identified as the Hemphillian cricetid Basirepomys pliocenicus (Wilson, 1937) (=Peromyscus pliocenicus Wilson, 1937) by Korth and De Blieux (2010) have been re-examined, and several distinct species are here recognized. Specimens from the early Hemphillian Rome fauna of Oregon are referred to a new, more primitive species of Basirepomys Korth and De Blieux, 2010, here named Basirepomys romensis, new species, which differs from other species of the genus in having lower-crowned cheek teeth and incomplete alternation of cusps on some molars. Specimens from the early Hemphillian Juniper Creek and Little Valley faunas of Oregon are referable to Paronychomys Jacobs, 1977, rather than Basirepomys, and represent a new species, Paronychomys shotwelli, which is distinguished from other species of the genus by its larger size and relatively longer lower third molar. A specimen previously referred to Peromyscus pliocenicus from the early Hemphillian of Kansas is referable to Paronychomys sp. Specimens identified as Peromyscus cf. pliocenicus from the late Hemphillian of California represent a new genus and species, Miotomodon mayi, which is distinguished from Basirepomys and Paronychomys by its higher-crowned cheek teeth, position of the ascending ramus on the mandible, and morphology of the mesoloph (-id) on the molars. Miotomodon is a probable ancestor for both Repomys May, 1981, and the Recent Neotomodon Merriam, 1898.