Open Paleo

Neimongosaurus

Zhang et al., 2001 nay-MOHN-go-SOR-us

Named after Nei Mongol (Inner Mongolia), the Chinese autonomous region where it was found, combined with Greek 'sauros' (lizard); meaning 'Nei Mongol lizard'.

89.8–66.0 million years ago Coniacian–Maastrichtian, Late Cretaceous
Late Cretaceous stages

Neimongosaurus is a genus of herbivorous therizinosaurian theropod dinosaur that lived in China during the Late Cretaceous period. Its fossils are known from the strata of the Iren Dabasu Formation. It is known from two specimens, discovered in 1999 by researchers from the Ministry of Land and Resources and described two years later. One species, N. yangi, is known, named after Chinese paleontologist Yang Zhongjian.

Under dispute

Neimongosaurus is an intermediate therizinosaur that falls inside or outside Therizinosauridae according to the definition used. Zanno (2010) and Hartman and colleagues (2019) recover it below the derived clade of Nothronychus, Segnosaurus and Erlikosaurus, outside the family as Zanno and colleagues (2009) define it, and Liao and colleagues (2026) recover it as an outgroup to the family. Kobayashi and colleagues (2022) recover it in the same position, with Erliansaurus, and include it in Therizinosauridae under their stem-based definition. It is placed in Therizinosauroidea.

Diagnosis

  1. Anterior caudal vertebrae with circular fossa under transverse process
  2. Radius with prominent biceps tuberosity
  3. Proximal pedal phalanges with well-developed heels
  4. Tibia with extremely long fibular crest exceeding half tibia length
  5. Lateral surface of preacetabular process twisted to face dorsally
  6. Caudal vertebrae with widely divergent prezygapophyses

Species

Neimongosaurus yangi Zhang et al., 2001

Type species

Named for Yang Zhongjian (also known as C. C. Young), the prominent Chinese paleontologist.

Holotype
LH V0001 , Long Hao Institute of Geology and Palaeontology
Material
Partial braincase, right dentary anterior end, most axial column except atlas/some mid-posterior dorsals/distalmost caudals, pectoral girdle (scapulocoracoids, furcula, humeri, left radius), pelvic girdle (partial ilia, femora, tibiae, left distal tarsals 3-4, most left pes)
Horizon
Iren Dabasu Formation, Coniacian–Maastrichtian, Late Cretaceous , 89.8–66.0 million years ago
Locality
Sanhangobi, Inner Mongolia, China

References

  1. Zhang, X. H.; Xu, X.; Zhao, X. J.; Sereno, P. C.; Kuang, X. W.; Tan, L. (2001). A long-necked therizinosauroid dinosaur from the Upper Cretaceous Iren Dabasu Formation of Nei Mongol, People's Republic of China. Vertebrata PalAsiatica 39(4): 282-290. zhang2001a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Theropods. Princeton University Press.

    Source of the hip height estimate, and the appearance features.

    jones2026c
  3. Zanno, L. E. (2010). A taxonomic and phylogenetic re-evaluation of Therizinosauria (Dinosauria: Maniraptora). Journal of Systematic Palaeontology 8(4): 503-543. doi:10.1080/14772019.2010.488045

    Re-evaluation of Therizinosauria placed Neimongosaurus outside Therizinosauridae as intermediate therizinosauroid.

    zanno2010a
  4. Kobayashi, Y.; Takasaki, R.; Fiorillo, A. R.; Chinzorig, T.; Hikida, Y. (2022). New therizinosaurid dinosaur from the marine Osoushinai Formation (Upper Cretaceous, Japan) provides insight for function and evolution of therizinosaur claws. Scientific Reports 12(1). Springer Science and Business Media LLC. doi:10.1038/s41598-022-11063-5

    New therizinosaurid description recovered Neimongosaurus with Erliansaurus as basal clade under broader definition.

    kobayashi2022a
  5. Hartman, S.; Mortimer, M.; Wahl, W. R.; Lomax, D. R.; Lippincott, J.; Lovelace, D. M. (2019). A new paravian dinosaur from the Late Jurassic of North America supports a late acquisition of avian flight. PeerJ 7: e7247. PeerJ. doi:10.7717/peerj.7247

    Recovered Neimongosaurus outside a clade of Nanshiungosaurus, Nothronychus, Erlikosaurus and Segnosaurus.

    hartman2019a
  6. Kobayashi, Y.; Zelenitsky, D. K.; Fiorillo, A. R.; Chinzorig, T. (2025). Didactyl therizinosaur with a preserved keratinous claw from the Late Cretaceous of Mongolia. iScience 28(4). Elsevier BV. doi:10.1016/j.isci.2025.112141 kobayashi2025a
  7. Zanno, L. E.; Gillette, D. D.; Albright, L. B.; Titus, A. L. (2009). A new North American therizinosaurid and the role of herbivory in 'predatory' dinosaur evolution. Proceedings of the Royal Society B: Biological Sciences 276(1672): 3505-3511. The Royal Society. doi:10.1098/rspb.2009.1029

    Defined Therizinosauridae as the least inclusive clade containing Nothronychus, Segnosaurus, Erlikosaurus and Therizinosaurus.

    zanno2009a
  8. Liao, C. C.; Freimuth, W. J.; Zanno, L. E.; Xu, X. (2026). A new therizinosaur from the Early Cretaceous Jehol Biota and ecomorphological patterns among early therizinosaurians. Journal of Systematic Palaeontology 24(2): 2710287. Informa UK Limited. doi:10.1080/14772019.2026.2710287

    Recovered Neimongosaurus as an outgroup to Therizinosauridae.

    liao2026a