自20世纪60年代,欧亚大陆晚新生代地层中陆续发现了p3由5个主要褶沟组成的兔类化石,并先后建立了上新五褶兔(Pliopentalagus Gureev et Konkova,1964)和三裂齿兔(Tris- chizolagus Radulesco et Samson,1967)两属。近年,在中国安徽淮南大居山新生代晚期不同时代的洞穴、裂隙堆积物中发现了保存相当完整,数量颇多的上新五褶兔的材料。笔者在研究大居山新洞早上新世的上新五褶兔时, 将其与欧亚大陆该属内的已知种和三裂齿兔的各种进行了详细比较,发现产自河北省阳原县泥河湾盆地晚上新世稻地组的Pliopentalagus nihewanensis Cai,1989被指定为上新五褶兔值得商榷。Pliopentalagus nihewanensis的材料仅有1枚p3(GMC V 2008-1)和两枚中间颊齿(p4 或ml,GMC V 2008-2及m2,V 2008-3)。正型标本p3的中前褶沟(AR)中央、后外褶沟和后内褶沟后壁釉质层具有小褶曲,这些形态确实与上新五褶兔的特征有些相似。但褶曲的发育程度明显比上新五褶兔的弱;另外,其齿冠舌侧后缘向后内突出,后外褶沟和后内褶沟较平直并近与齿纵轴垂直,后外褶沟与后内褶沟深度相近等而与上新五褶兔也有所不同。褶沟的釉质层在两枚中间颊齿中较平直,与上新五褶兔显然也有较大的区别。就该p3而言,可以认为它属于一枚釉质构造极简单的上新五褶兔的前臼齿,也可以认为是釉质构造很复杂的三裂齿兔的p3。研究表明,在上新五褶兔和三裂齿兔的系统演化过程中,其颊齿褶沟釉质层的构造有越来越复杂的趋向。作为上新世较晚期的“Pliopentalagus nihewanensis”的p3,指定为上新五褶兔显然有悖于该属釉质构造在地史中越来越复杂的演化事实,而指定为三裂齿兔则正好与该属釉质构造的演化趋势相符(Averianov and Tesakov,1997)。另外,从共生动物群和动物的生活习性看,安徽淮南发现的上新五褶兔与大量现代东洋界特有的类型共生(如Tupaiidae�
Promimomys asiaticus sp. nov., the first known species of the genus in East Asia, is described. The material was collected from the early Pliocene cave deposit in Daju- shan Hill, Huainan, Anhui Province. Promimomys was first found in Europe and considered as the ancestor of the family Arvicolidae. The new species from China is distinct from the type species, P. cor, and other known species in its thicker enamel of uniform thickness, simple anterior loop of m1, and blunt, salient angles. It is more primitive than other known species in Europe and North America and also more primi- tive than Mimomys bilikeensis of early Pliocene of Inner Mongolia. It is thus the earliest and the most primitive arvi- colid rodent known. The discovery of Promimomys asiaticus sp. nov. is significant to the study on the origin and the phy- logeny of arvicolids, and to the discussion of the interconti- nental dispersal events of arvicolids.
