内蒙古二连盆地沙拉木伦地区中始新世全脊貘(Teleolophus)(奇蹄目:貘超科)头后骨骼研究（英文）

Postcranial morphology of Middle Eocene deperetellid Teleolophus(Perissodactyla, Tapiroidea) from the Shara Murun region of the Erlian Basin, Nei Mongol, China

戴氏貘科(Deperetellidae)是亚洲中始新世地层中常见且特有的貘类,目前包括了5个属。但已知的戴氏貘材料大部分都是破损的上、下颌骨,仅有Deperetella保存有部分头后骨骼。仅依据牙齿的特征,戴氏貘在貘超科中的系统发育位置有很大争议,比如沼貘科的Colodon,脊齿貘(lophialetids)或红山貘(rhodopagids)都被认为可能和戴氏貘有较近的亲缘关系。最近几年,在内蒙古二连盆地不同地点和层位采集到数量丰富的戴氏貘化石,其中包括头骨和头后骨骼材料。本文即是对其中采自沙拉木伦地区乌兰胡秀地点全脊貘(Teleolophus)头后骨骼的研究报告,材料包括前足、后肢及后足。通过对全脊貘头后骨骼的形态描述,以及和相关类群(Deperetella,Lophialetes,Heptodon,Helaletes和Colodon)的比较,表明全脊貘属和戴氏貘属具有很多相似特征,支持了两者具有较近的亲缘关系。这些特征主要包括长而纤细的四肢,后足三趾;月骨较长而窄,其近端桡骨关节面内侧缘略凹;巨骨近端的头状隆起位置靠前,外侧具有和Mc IV的关节面;股骨滑车略微不对称;腓骨非常退化,甚至和胫骨愈合;Mt III与骰骨关节;Mt II主要在后方与外楔骨关节。虽然全脊貘头后骨骼也有一些和脊齿貘(Lophialetes)相似的特征,但考虑到两者臼齿上明显的区别,它们在骨骼上的相似特征可能归因于平行演化的结果。和全脊貘相比,Colodon的头后骨骼和Heptodon的更为接近,表明后两者具有更近的亲缘关系。但戴氏貘科在貘超科中的系统发育位置以及和沼貘科(Helaletidae)的亲缘关系,仍需进一步的研究工作。形态特征和后肢的"三元图"分析都表明,全脊貘已经具有较为快速的奔跑能力,这和同时期的脊齿貘相似。

Deperetellidae are a group of common,endemic Asian Middle Eocene tapiroids.Although five genera within the family have been named,most of them were represented by fragmentary maxillae and mandibles except for some skeletal material of Deperetella.Based exclusively on dental characters,different authors have proposed affinities of deperetellids with,for instance,helaletid Colodon,lophialetids,or rhodopagids.Here we described the partial postcranial skeleton of Teleolophus medius?recently discovered at Wulanhuxiu(=Ulan Shireh)of the Erlian Basin,China,and compared the postcranial skeletons of Teleolophus with those of Lophialetes,Deperetella,Heptodon,Helaletes,and Colodon.The postcranial skeleton of Teleolophus shares many similarities with that of Deperetella especially in having elongated and slender limbs,a relatively long,narrow lunar with a slightly concave medial border of the radial facet,a magnum with an anteriorly situated hump and a deeply excavated Mc IV facet,a slightly asymmetric trochlea of the femur,a fibula highly reduced or even fused with a tibia,Mt III contacting the cuboid,Mt II in contact with ectocuneiform only on the posterior end,and the pes with functional tridactyls.These similarities support the close relationship between Teleolophus and Deperetella.We interpreted some similarities of postcrania between Teleolophus and Lophialetes as a result of parallel evolution,due to their cursorial adaptations.Colodon is more similar to Heptodon than to Teleolophus in the postcranial features,suggesting a close relationship between Colodon and Heptodon.Whether or not Helaletidae and Deperetellidae are closely related await further investigation.Both morphological characters and ternary diagram indicate that Teleolophus adapted to fast running,as its contemporary Lophialetes.