A new thalattosaur, Concavispina biseridens gen. et sp. nov., is established on the basis of a new skeleton from Xiaowa Formation of Guangling, Guizhou, China. It is diagnosed by two rows of blunt teeth on anterior part of maxilla and V-shaped notch on the dorsal margin of neural spines in dorsal vertebrae. It shares three derived characters only with Xinpusaurus: anterior end of maxilla curved dorsally; cervical vertebrae less than five; proximal end of humerus wider than distal end. This indicates that the new taxon may have a closely relationship with Xinpusaurus.%简要记述了产自贵州关岭小凹组的一具基本完整的骨架,在此基础上建立了海龙类的一个新属种,双列齿凹棘龙(Concavispina biseridens).新种最明显的鉴定特征是:上颌骨前端有两列钝的牙齿,后部无齿;脊椎神经棘背缘形成Ⅴ形缺口.凹棘龙与新铺龙(Xinpusaurus)独有的衍征包括上颌骨前段背向弯曲,颈椎数目小于5枚,肱骨近端比远端宽.这些特征指示凹棘龙与新铺龙可能具有较近的亲缘关系.
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