贵州中三叠世安顺龙(爬行纲:海龙目)一新种

摘要

A new species of the thalattosaur genus Anshunsaurus is described from the Zhuganpo Member of the Falang Formation, Ladinian. It differs from the geologically younger Anshunsaurus huangguoshuensis (from the Wayao Member of the Falang Formation, lower Carnian) in many morphological characteristics as well as in a smaller size at adult stage. Both occurrences are in the marine Triassic of southwestern Guizhou Province, China.%中国的海龙类以前仅发现于法郎组瓦窑段,包括安顺龙和新铺龙两属.最近在法郎组竹杆坡段也发现了海龙化石(完整的骨架,中国科学院古脊椎动物与古人类研究所标本编号V 13782),被归入安顺龙属.标本产自贵州兴义乌沙,时代是中三叠世拉丁期. 此标本小于黄果树安顺龙两个已知标本,但是根据以下特征判断应该是个成年个体:头骨相对较小,许多骨缝愈合,髓椎线(neurocentral suture)封闭,肱骨上各种结构已经显著分化,掌骨和跗骨骨化程度高.根据以下特征建立一新种,乌沙安顺龙(Anshunsaurus wushaensis sp.nov.):头骨相对较小(相对肩臼至髋臼长度);轭骨后突短,向后延伸不超过下颞孔之半;后背区的神经棘高度小于宽度,其背缘有垂向沟、脊;间锁骨十字形,前突基部宽;肱骨外髁沟明显,内髁很发育,在内腹侧有脊但无孔;第五掌骨比第四掌骨稍长;第四指失去一个指节;髂骨板向后背向展开;7个跗骨骨化.