First Discovery Of Fossil Episiphneus (Myospalacinae, Rodentia) From Northeast China

The first Episiphneus (Myospalacinae, Rodentia, Mammalia) fossils of the Late Pliocene from Northeast China are described here as E. dalianensis sp. nov., which were collected from the lowermost fossiliferous deposits from Jinyuan Cave of Luotuo Hill in Dalian, Liaoning Province. The new fossils include intact skull, mandibles and molars with roots. The skull is characterized by a flat occiput and the supra-occipital process cohering with the lambdoid crest; meanwhile distinctive dental features include rooted molars and anterior cap of m1 coated with enamel. The new species is morphologically distinct from those of the tribe Prosiphneini with convex occiput, as well as species of the tribe Mesosiphneini with occipital concavity; and should be referred to the genus Episiphneus of the trible Myospalacini. Episiphneus was previously represented by a single species, E. youngi, whose geographical distribution is restricted to North China during the Early Pleistocene, such as Zhoukoudian Locality18 (ZKD Loc.18), Beijing. The Jinyuan specimens are similar to E. youngi in cranial dome of both species bear flat occiput without interparietal, rooted hypsodont molars, and appreciably reduced M3/m3. Nonetheless, there are also differences in morphology between the new species and E. youngi, the type species of Episiphneus. For example, E. dalianensis sp. nov. is slightly smaller in size, with incisive foramen surrounded by premaxilla, and a well-developed 1st lingual reentrant angle (LRA1) on the M1. With relatively smaller size, rooted molars, thick enamel and developed enamel lakes formed by the reentrants, E. dalianensis sp. nov. is apparently more basal to Myospalax prosilurus and Myospalax psilurus. All the three species have the incisive foramen surrounded by premaxilla, the evident 1st lingual reentrant angle (LRA1) on the M1, obviously reduced M3/m3, and overlapping geographical distribution, suggesting that E. dalianensis sp. nov. represents a putative ancestor of the two others. As the first discovery of fossil Episiphneus from Northeast China, E. dalianensis sp. nov. is also the earliest and most primitive species of the genus. Its discovery has significant implications for reconstructing the origin, evolution and dispersal pattern of Myospalacinae in Northern China, as well as for discussing its palaeoecological variation.