A New Genus of Cylindrodontid Rodent from the Chadronian (Late Eocene) of Southwestern Montana and a Reassessment of the Genus Pseudocylindrodon Burke, 1935

ABSTRACT The cylindrodontid rodent Pseudocylindrodon Burke, 1935, formerly included seven named species, but is here restricted to the type species P. neglectus Burke, 1935, two additional North. American species (P. citofluminis Storer, 1984, and P. lateriviae Storer, 1988), and the Asian species P. mongolicus Kowalski, 1974. The other three species previously assigned to Pseudocylindrodon are here referred to the new genus Dolocylindrodon: D. medius (Burke, 1938), D. tobeyi (Black, 1970), and D. texanus (Wood, 1974) based on a combination of cranial and dental morphology. Two new species of Dolocylindrodon are named from the Chadronian part of the Climbing. Arrow Formation of southwestern Montana: Dolocylindrodon vukae (type species of the genus) and Dolocylindrodon rahnensis. Additional specimens of D. medius from the early Chadronian McCarty's Mountain fauna of Montana are briefly discussed. The recognition of a new genus and two new species of cylindrodonts increases the known diversity of this family to 14 recognized species included in five genera during the North .American Chadronian, the time of greatest diversity of the family. Dolocylindrodon is viewed as a primitive member of the Cylindrodontinae that attained higher-crowned teeth independent of the more hypsodont Cylindrodon Douglass, 1901.