Abstract: Two partial skeletons are described from the Upper Cretaceous Iren Dabasu Formation of Nei Mongol that represent a new therizinosauroid theropod. Neimongosaurus yangi 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 long 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.

摘要： 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(Russell and Dong ,1994 ;Xu et al. ,1999) 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 ,1997 ;Makovicky and Sues , 1998 ;Xu et al. ,1999 ;Sereno ,1999) 。 新发现于内蒙古苏尼特左旗赛罕高