陕西洛南中晚更新世根田鼠化石

The Middle-Late Pleistocene fossils of Microtus oeconomus from Luonan County,Shaanxi Province,China

目的研究陕西洛南张坪洞穴群中发现的根田鼠化石M icccrotus oeconomus。方法运用经典古生物学方法,包括化石解剖、系统描述、形态对比、统计归纳。结果M3舌侧3褶沟4褶角;m1有4个封闭的三角,第5个与前帽贯通,后环位于齿列纵轴上;m3唇侧3褶角;M3和m1的长度、宽度从第6层洞到第1层洞逐渐变大,第6齿峡(Is6)的宽度变小。结论化石的主要特征可与周口店第1地点的M.epiratticeps相对比,主要测量值在现生种的变异范围之内,确定为中更新世以来不同时段的根田鼠化石,其颊齿趋于增大,第6齿峡趋于变窄。

Aim To research the fossils of Microtus oeconomus by screen-washing from Zhangping Caves in Luonan County, China. Methods Using the classical geology methods including measuring, statistics and comparing with other locality fossils. Results The m3 have 3 LRA and 4 LSA ; ml have 4 closed triangles and T5 fuse with AC ; the position of PL is on teeth line axes; M3 have 3 BSA. From C6 to C1, the L and W ofml and M3 are increased and the Is6 is reduced. Conclusion The fossils teeth resemble those of the M. epiratticeps from Choukoutien Locality 1, and their measure is in variations of the extant Microtus oeconomus. The dimensions indicate that their molars tendency has become enlarged and the 6th dentine isthmus tendency narrow gradually.