Erlianomys Combinatus, a Primitive Myodont Rodent from the Eocene Arshanto Formation, Nuhetingboerhe, Nei Mongol, China

摇 A new myodont rodent is reported from the lower part of the Arshanto Formation in Nuhe鄄 tingboerhe of Nei Mongol, which represents one of the earliest and most primitive myodont rodents in Asia. The new species is characterized by several primitive features, such as M1 and M2 subequal in size, anterior cingulum( id) pronounced and having weak or no connection with the protocone and protoconid, presence of a small p4 or dp4 in at least some individuals, the m1 anteroconid weak or absent, protoconid and metaconid isolated, anterolophulid absent, hypoconulid on m2-3 distinct, hypolophid short or extending to the hypoconulid on m2-3, ectolophid weak, mesoloph( id) absent or weak. The new species is most similar to the Asian Aksyiromys, Primisminthus yuenus and other species. The primitive features of the new species suggest that the common ancestor of Eocene myo鄄 donts is probably similar to Erlianomys and originated in Asia in Early Eocene. Key words摇 Nuhetingboerhe, Nei Mongol; Early Eocene; Arshanto Formation; myodont