贵州晚三叠世关岭生物群大型鱼龙化石一新属种

A new species of large-sized and long-body ichthyosaur from the Late Triassic Guanling biota,Guizhou,China

根据采自贵州关岭上三叠统小凹组下段两个分别具有完整骨架和呈立体保存的头骨标本,命名和描述为一种大型的长体型的鱼龙Panjiangsaurusepicharisgen.etsp.nov.。这类鱼龙以下颌后部缺齿,荐前椎数约69节,前肢边缘的凹口出现在桡骨、接桡骨和远端腕骨上为特征。Panjiangsaurus外鼻孔的骨片组成与中、晚三叠世Shastasaurus和Cymbospondylus的外鼻孔相似,肩带和腰带也具有晚三叠世卡尼期Shonisaurus的肩带和腰带的特点,但其桡骨、接桡骨和远端腕骨均发育有凹槽的前肢,可以与晚三叠世诺利期Macgonwani以及早侏罗世Stenopterygius的前肢相比较,而具有侏罗纪鱼龙的特征。

On the basis of a complete skeleton specimen and a nearly three-dimensional skull specimen collected from the Lower Member of the Upper Triassic Xiaowa Formation at Xiaowa Village,Xinpu,Guanling County,Guizhou Province,a new species of large-sized,long -body ichthyosaur —Pan-jiangsaurus epicharis gen.et sp.nov.—is named and described in detail.The new ichthyosaur is character-ized by the absence of the teeth in the posterior half of the dentary on the lower jaw,possession of ca.69presacral vertebrae and appearance of a notch in the anterior axial margin of radius ,radiule and distal carpus.It dif fers from all other shastasaurids except Shonisaurus and Callawayia in the shape of the cora-coid with an essentially straight medial margin and also in the larger radius than the ulna.Panjiangsaurus differs from Shonisaurus and Callawayia in the relatively longer vertebrae and obvious intermedium.This new taxon differs from Shastasaurus in the lack of a small notch in the leading edge of the humerus.Compared with Cymbospondylus,the latter has a premaxilla with long processus supranarialis,and the nasal reaches posterior to contact postfrontal.