A new prosciurine rodent from Shantung Province, China

Abstract

A lower molar of a new species of rodent, Prosciurus? shantungensis, from the subsurface of eastern China adds to the diversity of the known Asian prosciurine aplodontids and increases the likelihood that aplodontids were widespread in Eurasia during the Oligocene. This form is structurally close to the North American prosciurine aplodontids, especially Prosciurus relictus from the middle Oligocene. The metaconid is strongly compressed and reduced in height, a condition partially developed in P. relictus but here more extreme. Height of the mesoconid and the degree of lophodonty are more advanced than in North American species of Prosciurus. P.? shantungensis differs from the prosciurine-like lower dentitions from Kazakhstan and Mongolia described by Argyropulo (1939) and Kowalski (1974) in crest development and in details of the cusp morphology. Types of the Asian prosciurine or presumed prosciurine species are upper dentitions for which associated lower dentitions are unknown, yet the slope of the crests in Prosciurus lohiculus is too low to match the occlusal surface in P.? shantungensis and the degree of lophodonty in P. arboraptus is less than would be expected for the upper dentition of the Shantung form.