内蒙古赤峰初头朗早更新世哺乳动物群的新材料及二元相似性分析

摘要

出土于内蒙古赤峰初头朗小南山地点的哺乳动物化石新材料有直隶犬(Canis chihliensis),泥河湾披毛犀(Coelodonta nihowanensis),中国长鼻三趾马(Hipparion (Proboscidipparion) sinense),三门马(Equus sanmeniensis),李氏野猪(Sus lydekkeri),湖麂相似种(Muntiacus cf.M.lacustris),山西轴鹿(Axis shansius),布氏真枝角鹿(Eucladoceros boulei),翁氏转角羚羊(Spirocerus cf.S.wongi)及古中华野牛(Bison palaeosinensis).加上此前在初头朗东梁、东村北沟和东村南沟3个地点出土的标本,初头朗一带出土的哺乳动物化石种类增加到30个.初头朗4个地点的哺乳动物化石产自同一层位,属于同一个动物群.根据动物群的二元相似性系数,初头朗动物群在组成上最接近狭义泥河湾动物群.综合Brainerd-Robinson排序结果、动物群古老系数和动物群中绝灭种类的百分比,初头朗动物群的时代介于狭义泥河湾动物群和柳城巨猿洞动物群之间;而根据与相关动物群年龄值的对比,初头朗动物群的年龄值约在1.4-1.6 Ma之间.初头朗动物群中的食肉目种类有1 1个,但大多为小型种类.奇蹄目和偶蹄目种类的总和占动物群总数的一半,大多为体型较大的种类.该动物群中的嫩食者和林柄者指示当时存在一定范围的森林和林地;而动物群中的粗食者及开阔地栖息者指示当时存在面积较大的草原和草甸.初头朗动物群的大部分种类是喜温动物,喜冷种类只有鼠兔和披毛犀,因此当时的气候与现今大致相同.在地理位置上初头朗动物群是我国最靠北和最靠东的早更新世动物群,因此可以推荐为东北地区的早更新世哺乳动物群典型地点.%New specimens from a new locality at Chutoulang in eastern Nei Mongol were identified as Canis chihliensis,Coelodonta nihowanensis,Hipparion (Proboscidipparion) sinense,Equus sanmeniensis,Sus lydekkeri,Muntiacus cf.M.lacustris,Axis shansius,Eucladoceros boulei,Spirocerus cf.S.wongi and Bison palaeosinensis.They enriched the mammalian fauna of Chutoulang to 30 taxa together with the material from Dongliang,Dongcun Beigou and Dongcun Nangou localities.The mammalian fossils from these four localities are all from the same horizon and can be regarded as the same fauna,i.e.Chutoulang fauna.The composition of Chutoulang fauna is the closest to that of Nihewan (s.s.) by binary faunal similarity coefficients.The age of Chutoulang fauna is between those of Nihewan (s.s.) and Juyuandong at Liucheng according to Brainerd-Robinson's sequence,extinction rates and antiquity coefficients.The numerical age of Chutoulang fauna is estimated between 1.4-1.6 Ma based on those of compared faunas.Carnivora are the most numerous in Chutoulang fauna with 11 taxa,but mostly the small sized ones.Perissodactyla and Artiodactyla make about half of the fauna.They are mostly large sized forms.The presence of numerous browsers or forest dwellers implies the existence of forest or woodland in Chutoulang area during that period.The presence of grazers and openland dwellers indicates the existence of larger area of grassland or steppes than that of woodland or forests.Most members of Chutoulang fauna are temperate habitat dwellers with a few cold-prone forms such as Ochotona and Coelodonta.The climate in Chutoulang area in the Early Pleistocene was thus similar to that of today.Chutoulang fauna is the most northeastern Early Pleistocene fauna in China and it can be recommended as a type site of the Early Pleistocene mammalian fauna in northeastern China.