10.5479/si.1943-6688.103 William W. Korth William W. Korth Robert J. Emry Robert J. Emry Clint A. Boyd Clint A. Boyd Jeff J. Person Jeff J. Person Rodents (Mammalia) from Fitterer Ranch, Brule Formation (Oligocene), North Dakota The Smithsonian Institution 2019 rodents mammalia North Dakota, USA Prosciurus Altasciurus Heliscomys Eumys Paleontology 2019-09-12 14:34:51 Book https://smithsonian.figshare.com/articles/book/Rodents_Mammalia_from_Fitterer_Ranch_Brule_Formation_Oligocene_North_Dakota/9761732 Eighteen rodent species are recognized from the Fitterer Ranch fauna of North Dakota on the basis of more than a thousand collected specimens. Of the species recognized, four are new: the prosciurine aplodontiids <em>Prosciurus hogansoni </em>and <em>Altasciurus leonardi</em>, the heliscomyid <em>Heliscomys borealis, </em>and the cricetid <em>Eumys lammersi</em>.<br>A previously described castorid from this fauna, <em>Oligotheriomys primus </em>Korth, 1998, is considered a synonym of “<em>Eutypomys</em>” <em>magnus </em>Wood, 1937, on the basis of the recovery of lower dentitions but is retained in the genus <em>Oligotheriomys</em>. A single specimen is questionably referred to <em>Microparamys</em>, a genus elsewhere limited to the Eocene (Clarkforkian-Chadronian land mammal ages). The rodent fauna appears to be a combination of predominantly Orellan and Whitneyan species (early Oligocene), suggesting that the section might transcend the Orellan-Whitneyan boundary. However, the rodent fauna does not alter significantly from the lowest to the highest horizons. <br>