Middle Pleistocene Hamster Fossils From Locality 2 Of Shanyangzhai In Qinhuangdao Area,China

Shanyangzhai fossil site lies in a limestone quarry in Shanyangzhai Village,Haigang District,Qinhuangdao City,Hebei Province of China.By now,four independent fossil sites have been found in this quarry,and according to the order from south to north,these sites are named as Locality 1,2,3,4 of Shanyangzhai.Among them,Locality 2 has the most abundant fossil materials,and even though comparing it to other fossil sites in the same period(late Middle Pleistocene or Late Pleistocene)of it in northern China,this abundance is also rare.Up to now,there have been found 55 mammal species at the site,of which 46 species are small mammals,and some small mammals often have hundreds of pieces of materials.The present article focuses on the rich collection of hamster materials collected from this site.Specific results of research include:],According to the fauna's age that previous researchers speculated from the com-parison of members of the fauna and absolute age nmeasure,and the absolute age that measured recently by ESR(Electron Spin Resonance),that present author believes that the age of the fauna from Locality 2 is in the late Middle Pleistocene or Late Pleistocene,and more inclined to the former.2,A total of 1625 pieces of hamster materials of the fauna were systematically stud-ied.At the same time,more than 200 pieces of recent Cricetinae species were observed for comparing with the fossil materials.?There have been identifried 3 hamster species belonging to 2 genera from the fossil materials,namely Tscherskia triton,Cricetulus longicaudatus and C.barabensis.All of them are recent species.?Compared differ-ences between C.varions and T.triton detailedly from three aspects——molar's size.shape and structure,and the results showed the differences between them are very small.So,it suggests C.varicans should be discarded as T.triton's junior synonym.And since C.varians is type species of Cricetinus,Cricetinus should also be discarded as junior synonym of Tscherskia.Thus,except C.varians,the remaining 6 species(C.europaeus,C.gritzai,C.beremendensis,C.janossyi,C.koufosim C.mesolophidus)belonging to Cricetinus should also be transposed in Tscherskia.The diagnoses of Tscherskia are also given in the paper.According to the distribution and first emergence time of Tscher-skia species,it is tentatively believed that the genus originated from Europe in Early Pli-ocene and then spread to Asia.?Through the observation on specimens from locality 2,the author holds that C.longicaudatus and C.barabensis all have 2 anteroconids and 1 anterolophulid.Those three so-called assemblage types on ml of these two species which put forward by predecessors——2 anteroconids and 1 anterolophulid,2 antero-conids and 0 anterolophulid,and 1 anteroconid and 1 anterolophulid——may only be a reflect of individual hamster' age,do not have taxonomic significance.On the basis of observing the extant specimens and summarizing previous achievements,this paper further defines the differentiations between C.longicaudatus and C.barabensis.These differentiations are mainly embodied in:the fore branch of rear yoke ridges on Ml-2 of C.barabensis are strong but those of C.longicaudatus are weak or inexistence,crown surface of m1 of C.longicaudatus is relatively more slender than that of C.barabensis,separation degree of anteroconid on ml of C.longicaudatus is commonly larger than that of C.barabensis,and the area under dentition on lingual side of mandible of C.longicaudatus has more pores than that of C.barabensis,etc.?On the basis of ana-lyzing the predecessors' viewpoints,it is further raised that Cricetulus was likely to originate from northern China in the Late Pliocene or Early Pleistocene and then spread to the surroundings gradually.3,Summarized genera and species of fossil hamster in the Quaternary period of China:there are a total of 12 species(not including a lot of indeterminate species,con-formis species,affinis species)belonging to 8 genera and 3 uncertain species.All of them belong to Cricetinae.4,Based on observation of the characteristics of molars of recent specimens,the search tables of molar's characteristics of recent hamsters(4 genera,6 species)in China were given.