河北阳原山神庙咀早更新世直隶狼(Canis chihliensis)新材料

于2006-2011期间的4次野外发掘中,在泥河湾盆地的山神庙咀遗址发现了大量犬科化石,材料包括残破颅骨、前颌骨、上颌骨、若干下颌骨及头后骨骼的主要部件,其中的头后骨骼是迄今在中国发现的早期犬属化石中最为完整的.依据有关形态特征和测量数据,将其归入直隶狼(Canis chihliensis).具体特征如下:体形较大,I3强大,P4窄长,原尖发育,M1前后向变扁并具宽阔的齿带状次尖,m1具下后尖和下内尖,相对其M1大小而言,上、下第二臼齿较大,m2下跟座宽阔等.其头部骨骼及牙齿测量数据与现代灰狼的较为接近,但头后骨骼数据较后者明显为小.该种的最大特征是其下臼齿舌侧齿尖的退化和P4窄长及M1前后方向变扁.但山神庙咀犬属材料的ml舌侧齿尖的发育程度变异较大,因此,仅仅依据ml的特征不足以区分直隶狼和拟豺(Xenocyon dubius (=Cuon dubius)),尽管后者的鉴定与分类问题尚存争议,但直隶狼与被归入拟豺的材料有更多相似之处,它们与非洲野犬(Lycaon pictus)差异很大.山神庙咀遗址化石层与邻近的小长梁遗址文化层时代相当或稍晚,大约为1.3 Ma.

NEW REMAINS OF CANIS CHIHLIENSIS(MAMMALIA,CARNIVORA) FROM SHANSHENMIAOZUI,A LOWER PLEISTOCENE SITE IN YANGYUAN,HEBEI

From 2006—2011,numerous Canis specimens were recovered from the newly discovered Shanshenmiaozui Locality in the Nihewan Basin.The material includes broken crania,premaxillae,maxillae,mandibles and postcranial skeleton with most of the elements preserved,and represents the most extensive and informative sample of early fossil Canis ever recovered in China.This material can be assigned to the species Canis chihliensis based on morphological and metric characters,including large size,robust I3,elongated P4 with anterior notch and well-developed protocone,M1 strongly mesiodistally compressed and with broad cingular hypocone,m1 with metaconid and entoconid(however small),M2 and m2 large relative to M1 and m1 respectively,and m2 with broad talonid.Measurements of the skulls and the teeth are similar to the equivalent measurements for Canis lupus,but those of the postcranial elements are smaller.Canis chihliensis is characterized by reduction of the lingual cuspids on the lower molars,an elongated P4,and a mesiodistally compressed M1.However,the first lower molars from Shanshenmiaozui are quite variable in the development of their lingual cuspids.This study shows that it is not easy to distinguish Canis chihliensis from Xenocyon dubius(=Cuon dubius) based exclusively on characters of the first lower molar,and the taxonomic status of the latter species is still open to question.Both of them differ greatly in morphology from the African hunting dog Lycaon pictus.Unlike in Canis chihliensis,the tooth dimensions of Xenocyon dubius are quite variable.The fossil bearing stratum at Shanshenmiaozui can be correlated with,but probably later than that at the neighboring Xiaochangliang Site,which has an age of ca.1.36 Ma.