Repomys

Abstract: Two vertebrate faunas of Pliocene age, the Walnut Canyon and Buckhorn local faunas, are described from sediments of the Gila Group in the Mangas basin in northern Grant County, southwestern New Mexico. Stratigraphic sections and lithologic descriptions are provided for the three unnamed formations in the upper part of the Gila Group that produced these two faunas. The Walnut Canyon local fauna includes one major locality, the Walnut Canyon Horse Quarry, and three smaller sites located 5 km southeast of Gila. The fauna is composed of 12 species of mammals, including one lagomorph, one rodent, two carnivores, two horses, one peccary, three camels, one cervid, and one antilocaprid. The most common members of the fauna are the equids Astrohippus stockii and Dinohippus mexicanus and two genera of camelids (Hemiauchenia and Alforjas). The remaining species in the fauna are represented by very small samples. A. stockii, D. mexicanus, the canid Vulpes stenognathus, the tayassuid d. Catagonus brachydontus, and the camelid Alforjas are typical of late Hemphillian (late Miocene and early Pliocene) faunas. Furthermore, the presence of A. stockii, D. mexicanus, and a true cervid are indicative of latest Hemphillian faunas. Two correlative latest Hemphillian faunas, the Yepomera fauna from Chihuahua in northern Mexico and the Palmetto fauna from the Bone Valley Formation in Florida, are earliest Pliocene in age (5.2- 4.5 Ma). The Buckhorn local fauna incorporates 14 sites located between 3 and 10 km northwest of Buckhorn. The fauna is composed of 27 species of vertebrates, including one fish, one frog, one salamander, two snakes, six birds, one lagomorph, four rodents, four carnivores, two horses, one peccary, two camels, one ruminant, and one proboscidean. The abundance of aquatic vertebrates in several of the Buckhorn sites, in particular frogs (Rana) and birds, including a flamingo (Phoenicopterus), rails, and ducks, as well as the lithology of the sediments, suggest a lacustrine depositional environment. The mammals from the Buckhorn local fauna are clearly indicative of a Blancan (Pliocene) age, and several species permit a more precise placement within the Blancan. The presence of the small hipparionine horse Nannippus and a primitive species of the arvicoline rodent Mimomys and the absence of Neotropical immigrants, suggest a pre-late Blancan age (older than 2.5 Ma). The occurrence of the horse Equus (Dolichohippus) simplicidens and a large species of Mimomys (subgenus Ogmodontomys) excludes very early Blancan faunas. The evolutionary stage of the rodents Mimomys (Ogmodontomys) d. M. poaphagus and Repomys d. R. panacaensis is most consistent with a late early or early middle Blancan age (4.0-3.0 Ma) for the Buckhorn local fauna. Broadly correlative early or middle Blancan faunas are Cuchillo Negro Creek and Truth or Consequences in New Mexico, Clarkdale and Verde in Arizona, Rexroad in Kansas, and Panaca in Nevada.

Abstract: Four species of rodents (two heteromyids and two cricetids) and one lagomorph are identified from the late Tertiary Sevier River Formation of Utah. The heteromyids include a new genus and species of heteromyine, Metaliomys sevierensis, which is intermediate in morphology between the Clarendonian and early Hemphillian Diprionomys Kellogg and the extant genera Liomys and Heteromys. A single specimen is referred to Diprionomys sp., cf. D. minimus (Kellogg). The cricetid Paronychomys lemredfieldi Jacobs is known from the Hemphillian of Arizona. The second cricetid is referred to a new genus Basirepomys. Peromyscus pliocenicus Wilson from the Hemphillian of California is designated as the type species of the new genus, to which the new species B. robertsi from Utah is referred. Basirepomys is viewed as intermediate between Peromyscus and the basal neotomyine Repomys May from the late Hemphillian and Blancan. The only lagomorph in the fauna is Hypolagus vetus (Kellogg). Four of the taxa recognized from...

Abstract: 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 Paronychomy...