内蒙古乌兰塔塔尔地区早渐新世梳趾鼠类头骨新材料

New skulls of ctenodactyloids from the Early Oligocene of Ulantatal,Nei Mongol,China

记述了4件采自内蒙古乌兰塔塔尔早渐新世地层的近乎完整的、上下颌咬合在一起的梳趾鼠类头骨化石,基于牙齿特征将新材料归于乌兰塔塔尔丘齿鼠(Bounomys ulantatalensis Huang,1985)。乌兰塔塔尔丘齿鼠与始新世梳趾鼠类钟健鼠(Cocomys)及外鼠(Exmus)相比,在头骨整体形态,门齿孔、眶下孔、蝶腭孔、听泡的大小,后鼻孔、泪孔、眶后突的位置,顶骨及外耳道的形态,下颌骨齿隙长短等方面有明显差别;与渐新世及以后的梳趾鼠类的头骨特征整体相似。通过对梳趾鼠类头骨特征的对比,认为从始新世至渐新世,梳趾鼠类颧-咬结构由始啮型转为豪猪型,咬合能力增强,更有利于处理粗糙的食物;听泡膨大,使得其更适应开阔环境。头骨上的这些变化可能是对始新世–渐新世转折期后全球气候干旱化的一种适应。

Ctenodactyloids are a group of rodents that is characterized by the combination of a protrogomorphous or hystricomorphous skull and a sciurognathous mandible.The earliest known ctenodactyloid rodent is Cocomys,reported from China during the Early Eocene,and ctenodactyloids were widely distributed in East and Central Asia during the Eocene and Oligocene.The four genera of living ctenodactyloids are restricted to areas in North and East Africa.The many known Paleogene ctenodactyloids are based on fragmentary specimens,while only fragmentary skulls are known for Tataromys,Yindirtemys and Bounomys in Oligocene ctenodactyloids,which provide only limited information.Here we report four complete skulls with articulated jaws of ctenodactyloids that were found from the Early Oligocene of Ulantatal,Nei Mongol,China.These specimens were recovered from the light brownish yellow clayey siltsand of the 12-meter level of the Ulantatal Main Section.Based on the teeth morphology,the new specimens are referred to Bounomys ulantatalensis(Huang,1985).The new materials described herein add important data on the skull morphology of Bounomys and provide new and reliable evidence for the understanding of the skull evolution of the ctenodactyloid rodents.