内蒙古上白垩统二连组一长颈的镰刀龙类(英文)

A LONG-NECKED THERIZINOSAUROID DINOSAUR FROM THE UPPER CRETACEOUS IREN DABASU FORMATION OF NEI MONGOL,PEOPLE'S REPUBLIC OF CHINA

镰刀龙类 (又称“懒龙”)是一类奇特的植食性兽脚类恐龙 ,化石记录主要局限于亚洲白垩纪地层中。由于镰刀龙类极其特化的形态和化石材料的局限性 ,这类恐龙的系统位置存在较多的争议。最近的发现 (RussellandDong ,1 994;Xuetal.,1 999)表明这类恐龙属于虚骨龙类 ,但其更为具体的系统位置依然存在争议 (Sues ,1 997;MakovickyandSues,1 998;Xuetal.,1 999;Sereno,1 999)。新发现于内蒙古苏尼特左旗赛罕高毕上白垩统二连组的镰刀龙类化石材料代表这类恐龙的一个新属种。杨氏内蒙古龙 (Neimongosaurusyangigen .etsp .nov .)的正型标本为一较为完整的骨架 ,是已知镰刀龙类当中第一件在同一个体中保存了大多数脊椎和几乎所有肢骨的标本。依据以下特征将内蒙古龙归入镰刀龙超科 :U形的下颌联合部、齿骨前端向下弯曲、齿骨前部没有牙齿、牙齿有一个收缩的基部、近圆形的齿根和叶形的齿冠、前部颈椎的神经脊低矮而轴向较长、后部颈椎背视呈X形、肱骨近端角状、肱骨有后转子、肱骨的尺骨髁和挠骨髁位于前部并为一狭窄槽分开、肠骨的耻骨柄细长而坐骨柄短以及跖部短。内蒙古龙的以下特征区别于其他镰刀龙类 :前部尾椎的横突下部有一圆形的窝 ,桡骨二头肌结节非常发育 ,后足趾节近端跟部非常发育 。

Two partial skeletons are described from the Upper Cretaceous Iren Dabasu Formation of Ner Mongol that represent a new therizinosauroid theropod. Neimongosaurus yanggi gen. Et sp.nov.,is the first therizinosauroid to preserve most of the axial column and nearly all of the long bones of a single individual. Distinctive characteristics of the new species include anterior caudal vertebrae with a circular fossa under the transverse process, radius with a prominent biceps tuberosity, proximal pedal phalanges with well developed heels, tibia with an extremely ong fibular crest that is much longer than the half length of the tibia, lateral surface of preacetabular process twisted to face dorsally, and caudal vertebrae with widely divergent prezygapophyses. Neimongosaurus displays a few characters that are not reported in other therizinosauroids but do occur in some advanced maniraptorians, such as highly pneumatized vertebra and derived shoulder girdle. Particularly the elongated neck and shortened tail provide further evidence for a close relationship between therizinosauroids and oviraptorsaurs.