Neimongosaurus
A small herbivorous therizinosaur from Late Cretaceous China.
Neimongosaurus, whose name means "Nei Mongol lizard," was a plant-eating theropod dinosaur from the therizinosaur group. It lived in what is now China during the Late Cretaceous, and its remains come from the Iren Dabasu Formation. Two skeletons were found in 1999 by a team from the Ministry of Land and Resources, and they were formally described in 2001. The only known species is *Neimongosaurus yangi*, named in honor of Chinese paleontologist Yang Zhongjian.
The first specimen, LH V0001, included a partial braincase, part of the right lower jaw, a nearly complete backbone (15 neck vertebrae, 4 back vertebrae, and 22 tail vertebrae), a furcula, both shoulder blades and coracoids, both upper arm bones, a left radius, fragmented hip bones, both thigh bones, both shin bones, left ankle bones, and a complete left foot. The second specimen, LH V0008, consisted of a fused sacrum made of six vertebrae and both hip bones. Both were taken to the Long Hao Institute of Geology and Palaeontology for study.
Neimongosaurus was a fairly small therizinosaur. In 2001, Zhang and colleagues estimated its length at 2–3 meters (6.6–9.8 ft). Gregory S. Paul, in 2016, put its length at 3 meters (9.8 ft) and its weight at 100 kilograms (220 lb).
Only the back part of the skull and the front half of the right lower jaw are known. The front of the lower jaw was U-shaped, like in ornithomimids, oviraptorosaurs, and most troodontids, rather than V-shaped as in other theropods. The very front of the dentary had no teeth. Behind that, there were five tooth sockets, but only the third held a functional tooth; the second socket contained an unerupted replacement tooth. The crowns of these teeth were flattened from side to side and had small serrations on the front and back edges. A small opening for nerves and blood vessels sat about 15 mm behind the jaw's front joint. The occipital condyle was very thin, only 12 mm wide, while the foramen magnum's condyle measured about 15 mm.
The backbone included seventeen preserved vertebrae. The first thirteen were likely neck vertebrae, and the researchers suggested there might have been fourteen in total—one of the longest necks among non-avian theropods, longer than *Nanshiungosaurus* (which had twelve or fewer). The axis and the next nine neck vertebrae had long centra with slightly concave fronts and strongly concave backs.
Quick Facts
- Taxon
- Neimongosaurus
- Type Species
- Neimongosaurus yangi
- Type Species Authority
- Zhang et al., 2001
Facts from the source article.
Lore & Background
In 1999, a team from the Ministry of Land and Resources, based in Hohhot, Inner Mongolia, was conducting field work at Sanhangobi, 20 km southwest of Erenhot. The strata they were working in belonged to the Iren Dabasu Formation, which has been variably dated to the Turonian, the Santonian, or the Campanian–Maastrichtian. The first specimen, LH V0001, consisted of a partially preserved braincase; the front of the right lower jaw; a nearly complete axial column comprising 15 cervical, 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. The second, LH V0008, consisted of a sacrum composed of 6 sacral vertebrae and both ilia. Both specimens were transported to the Long Hao Institute of Geology and Palaeontology for study. In 2001, Zhang Xiaohong, Xu Xing, Paul Sereno, Kwang Xuewen and Tan Lin assigned them to a new genus and species of therizinosaurid dinosaur, Neimongosaurus yangi, designating LH V0001 as the holotype.
Reader's Guide
Neimongosaurus represents a small-bodied therizinosaur from the Late Cretaceous of China, providing insight into the diversity and evolution of therizinosaurs. Its fossils, discovered in 1999 and described in 2001, include a partial skull, nearly complete vertebral column, and limb elements. The skull shows a U-shaped symphyseal region and an edentulous front of the dentary, similar to ornithomimids, oviraptorosaurs, and most troodontids. The vertebral column includes one of the longest cervical series known among non-avian theropods, with up to fourteen neck vertebrae. The appendicular skeleton shows features typical of therizinosauroids, such as an enlarged medial tuberosity on the humerus and a deflected deltopectoral crest. Its classification has been debated: the original describers considered it a fairly basal therizinosaur outside Therizinosauridae, but later analyses, including a 2019 study by Hartman et al., recovered it as a therizinosaurid within a clade with Erliansaurus, Suzhousaurus, and Therizinosaurus. A 2006 study on arm motion suggested Neimongosaurus could extend its arms considerably forwards, possibly aiding in reaching and grasping foliage.
Did You Know?
- Neimongosaurus is named after Nei Mongol, the Chinese name for Inner Mongolia.
- Its specific name, yangi, honors Chinese palaeontologist Yang Zhongjian.
- The holotype specimen includes a nearly complete left pes that is articulated.
- The species had a U-shaped symphyseal region in the lower jaw, unlike the V-shape of other theropods.
More in Late Cretaceous dinosaurs 1-24
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