Neimongosaurus (meaning "Nei Mongol lizard") is a genus of herbivorous therizinosaur theropod dinosaur that lived in Asia during the Cenomanian stage of the Late Cretaceous period in what is now the Iren Dabasu Formation.
Discovery and naming[]
Right rostral dentary from the holotype of N. yangi
Neimongosaurus is a therizinosauroid which is known from the holotype LH V0001, consisting of a partially preserved braincase; the front of the right lower jaw; a nearly complete axial column compromising 15 cervical (including the axis), 4 dorsal and 22 caudal vertebrae; a furcula; both scapulocoracoids; both humeri; left radius; fragmented ilia; both femora; both tibiae; left tarsals and a virtually complete and articulated left pes. A second specimen, LH V0008, consisting of a sacrum composed by 6 sacral vertebrae and both ilia, was assigned as the paratype. The specimens were collected in 1999 at Sanhangobi in Inner Mongolia from the Iren Dabasu Formation, dating from the Cenomanian stage.
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.
Desription[]
Life restoration
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).
Neimongosaurus was 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.
Neimongosaurus exhibits some features not seen in other therizinosaurians but found in some advanced maniraptorans, such as highly pneumatized vertebrae and a highly derived shoulder. In particular, the elongated neck and short tail suggest a close relationship between therizinosaurians and oviraptosaurians.
The shoulder girdle elements of Ny angi , including a complete, undistorted wishbone, were reconstructed and articulated to show a unique orientation of the glenoid fossa compared to other known theropods and birds. This fossa was oriented laterally with a slight ventral component. The enlarged scapular and coracoid margins are oriented dorsally and ventrally around the joint rather than anteriorly and posteriorly as in most other non-avian theropods and birds. This reconstruction, along with an associated humerus, was used to determine the range of motion of the glenohumeral joint. The unusual morphology of the scapular and coracoid margins restricted the total range of motion in the dorsoventral direction, although the lateral position of the glenoid allowed for more extensive dorsal travel of the humerus. The humerus was also capable of considerable anterior protraction. Such extensive protraction is very different from the flight motion of extant birds, indicating that this glenoid morphology was most likely not an evolutionary transition to the morphology of modern birds. Neimongosaurus may have used this ability to extend its arms considerably forward for other activities such as reaching and grasping foliage. It measured approximately 2.3 meters (7.5 ft) in length and weighed about 90 kilograms (200 lb).
Classification[]
The original describers of the genus assigned Neimongosaurus to the Therizinosauroidea, in a basal position. Subsequent cladistic analyses have indicated a position in the more derived Therizinosauridae, but an analysis in 2010 by Lindsay Zanno recovered the original placement. However, Hartman et al. 2019 recovered Neimongosaurus as a therizinosaurid again. Below are the results:
| Therizinosauridae |
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Paleobiology[]
Sara Burch, in a 2006 conference abstract, presented the estimated range of motion in Neimongosaurus, with the motion at the glenoid-humeral joint being a rough circle, directed sideways and slightly downwards. This is different of the ovular backwards-downwards ranges in other theropods. This ability to extend their arms considerably may have helped it grasp for vegetation.
Appearance in other media[]
Jurassic Park[]
- Neimongosaurus was going to appear in Jurassic World: Primal Ops. However it was never added due to the game's closure in October 31st, 2022.
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