贵州兴义中三叠世黔鱼龙属(爬行纲:鱼龙目)一新种

A New Species of Qianichthyosaurus(Reptilia: Ichthyosauria)from Xingyi Fauna(Ladinian,Middle Triassic) of Guizhou

描述产于贵州省兴义市乌沙镇中三叠统拉丁阶法郎组竹杆坡段的鱼龙类黔鱼龙属一新种——兴义黔鱼龙(Qianichthyosaurus xingyiensis sp.nov.),并厘定黔鱼龙属(Qianichthyosaurus)的鉴定特征:齿冠长度与头骨宽度之比略小于0.1;尺骨外边缘呈片状或具凹缺;后肢近等或略长于前肢;胫骨外边缘呈片状或具凹缺。新种与Qianichthyosaurus属型种区别在于:吻部与头骨长度之比大于60%;肱骨远端桡骨关节面明显长于尺骨关节面;耻骨孔未闭合;腓骨后缘有一明显突起;坐骨亚三角形,缺少骨干。新种产出地层层位明显低于属型种的上三叠统卡尼阶法郎组瓦窑段,为目前发现的黔鱼龙属出现的最低层位。黔鱼龙属、贵州鱼龙属与海龙类安顺龙属在兴义和关岭均有发现,揭示中三叠世拉丁晚期的兴义动物群和晚三叠世卡尼期的关岭生物群可能有更紧密的关系。

A new species of Qianichthyosaurus Li, 1999 from the Zhuganpo Member of the Falang Formation （Ladinian, Middle Triassic）, Wusha Town, Xingyi City of Guizhou is described here, namely Qianichthyosaurus xingyiensis sp. nov. The recognition of the new species revises the diagnosis of the genus： tooth size relative to the skull width slightly below 0.1; ulna peripheral ＂shaft＂ notched or largely reduced; hindlimb nearly equal or longer than forelimb; tibia peripheral ＂shaft＂ notched or largely reduced. Qianichthyosaurus xingyiensis sp. nov. differs from the type species in having relatively longer snout （snout length/skull length over 60%）; humerus radial facet being prominently larger than ulnar facet; unenclosed obturator foramen on pubis; fibula posterior process on the posterior margin and the ischium sub-triangular lacking shaft. The new species is stratigraphically older than Q. zhoui, the specimens of which were exclusively known from the Wayao Member of the Falang Formation （Carnian, Late Triassic）. Along with askeptosaurid thalattosaur Anshunsaurus and shastasaurid ichthyosaur Guizhouich- thyosaurus, the occurrence of Q. xingyiensis sp. nov. in Xingyi Fauna suggests a closer relationship between Xingyi Fauna （late Ladinian, Middle Triassic） and Guanling Biota （Carnian, Late Triassic）.