FIRST URSINE BEAR MATERIAL FROM DONGXIANG,GANSU——Addition to the Longdan Mammalian Fauna(2)

Two bear specimens obtained from Dongxiang area were noticed from the purchased"dragon bones"of the Hezheng County in 2006:a complete mandible(HMV 1422) and a skull in association with its mandible(HMV 1454).They represent the first bear material of the Longdan mammalian fauna. Although slightly different in morphology,they are found to be very close to Ursus(Protarctos) yinanensis described by Li Yizheng in 1993,and thus referred to this species.A revised diagnosis of this species is given in the text. Based on high degree of genetic homogeneity and short divergence time of the 6 extant ursine species, molecular and biochemical biologists are being increasingly confident that all the extant ursines should be assigned to a single genus,Ursus.On the other hand,most of the paleontologists,governed by their factual knowledge of morphologic distinctions between these ursine species,are inclined to separate them into different genera.Nevertheless,the Eurasian Pliocene-Early Quaternary bear fossils have often been indiscriminately referred to Ursas.A closer observation of the bear materials during our comparative study of the Dongxiang bear specimens revealed great variety in bear ml morphology,implying its particular importance in classification of the Ursinae.Based mainly on ml morphology,coupled with other skull and dental features,the majority of the Eurasian Pliocene-Early Quaternary bears can possibly be divided into three groups:1) The bears having simple ml's,lacking pre-metaconids and pre-entoconids,with the transverse groove surfaces being basically smooth.2) Those having ml's with pre-metaconids and V-,Y-,or X-shaped ridges on the transverse grooves,but no pre-entoconids.The ml morphology of this group is close to that of the extant black bears.3) Those having ml's with bunodont pre-metaconids,pre-entoconids and well developed accessory cusplets.The ml morphology of this group is basically that of the extant brown bears.The 1~(st) group includes the specimens from Baroth-K(o|¨)pecz, Yinan(and Dongxiang),and the left hemimandible of Serrat d'en Vacquer described in 1890.The 2~(nd) group includes those from Perrier,Weze,Layna,W(o|¨)lfershein,etc.,and the skull and mandible from Serrat d' en Vacquer described in 1892.The 3~(rd) group includes U.etruscus of many European localities,among which Val d' Arno and St.Vallier are the principal ones.Morphologic distinctions between,and the degree of variability within,these three groups strongly inclined us to separate them into different genera.If the above viewpoint is tenable,three generic names would be suitable for them:Protarctos,Euarctos and Ursus.In this case,Protarctos would include P.boeckhi(MN 14),P. ruscinensis(MN 15) and P.yinanensis(equivalent to MN 16-17).Euarctos would include E.pyrenaicus (MN 15),E.minimus(MN 16-17) and the extant American and Asian black bears.Ursus would contain U.etruscus(MN 17),U.spelaeus etc.,and the extant brown bear(and possibly U.maritimus).