Based on these remains, the type species, Neimongosaurus yangi, was formally named and described by Zhang Xiaohong, Xu Xing, Paul Sereno, Kwang Xuewen and Tan Lin in 2001. The generic name is derived from Nei Mongol, the Chinese name for Inner Mongolia. The specific name honours Yang Zhongjian.[1]
Neimongosaurus is thought to have been a small-sized therizinosaur, from 2.3 to 3 m (7.5 to 9.8 ft) in length and weighing 91 to 227 kg (201 to 500 lb).[2][3]
Neimongosaurus was a bipedal and ponderous animal with well developed hindlimbs. The femur measured 36.6 cm (366 mm) long, having a straight shaft, the femoral head points to the inner sides. Both tibiae are preserved, measuring 31 cm (310 mm); shorter than the femur. Its lower jaw is U-shaped, preserving only a partial right dentary. There are 5 alveoli in which only one tooth was preserved. It is coarsely serrated, indicating a herbivorous diet like other therizinosaurs, such as Alxasaurus or Erlikosaurus. It had a relatively elongated neck composed by approximately 16 cervicals (if preserved atlas). Overall, the forelimbs are well preserved, missing the manus. Its scapula had a tapering end.[1]
Classification
The original describers of the genus assigned Neimongosaurus to the Therizinosauroidea, in a basal position.[1] Subsequent cladistic analyses have indicated a position in the more derived Therizinosauridae,[4] but an analysis in 2010 by Lindsay Zanno recovered the original placement.[5] However, Hartman et al. 2019 recovered Neimongosaurus as a therizinosaurid again. Below are the results:[6]
In a 2006 conference abstract, Sara Burch presented the inferred range of motion in the arms of the therizinosaur Neimongosaurus and concluded the overall motion at the glenoid-humeraljoint at the shoulder was roughly circular, and directed sideways and slightly downwards, which diverged from the more oval, backwards-and-downwards-directed ranges of other theropods. This ability to extend their arms considerably forwards may have helped Neimongosaurus reach and grasp for foliage.[7]
^Paul, G. S. (2016). The Princeton Field Guide to Dinosaurs (2nd ed.). Princeton, New Jersey: Princeton University Press. pp. 151−152. ISBN9780691167664.
^Senter, P. (2007). "A new look at the phylogeny of coelurosauria (Dinosauria: Theropoda)". Journal of Systematic Palaeontology. 5 (4): 429–463. doi:10.1017/S1477201907002143. S2CID83726237.