Open Paleo

Yimenosaurus

Bai et al., 1990 yee-MUHN-o-SAWR-us

Named after Yimen County (also written as Yiman) in Yunnan Province, China where it was found, combined with Greek sauros meaning 'lizard'; translates as 'Yiman reptile'

201.4–174.7 million years ago Hettangian–Toarcian, Early Jurassic
Early Jurassic stages

Yimenosaurus is an extinct genus of plateosaurid sauropodomorph dinosaur that lived in China in the Early Jurassic. The genus was first named in 1990 by Ziqi Bai, Jie Yang and Guohui Wang, along with its type and only species, Yimenosaurus youngi. The species name honors renowned Chinese paleontologist Yang Zhongjian, the father of Chinese paleontology, known as C.C. Young in English. Known material includes the holotype, an almost complete skull and mandible, as well as incomplete cervical and dorsal vertebrae, a mostly complete sacrum, an ilium, ischia, partial ribs and complete femur, and a paratype, a well-preserved postcrania with a fragmentary skull. In 2010 Paul estimated its length at 9 meters (30 ft) and its weight at 2 tonnes (2.2 short tons).

Under dispute

Yimenosaurus youngi was assigned to Plateosauridae by Bai and colleagues (1990) in its original description, and has not since been scored in a numerical phylogenetic analysis, so the placement remains provisional.

Diagnosis

  1. Moderate to large prosauropod attaining nine meters in length with relatively delicate skull
  2. Cranial construction with relatively long and gracile elements composing the skull
  3. Elliptical external nares and large triangular antorbital fenestra
  4. Premaxilla and ascending process of maxilla relatively well developed with shortened ventral dental margin
  5. Mandible relatively delicately constructed with well-developed mandibular fenestra positioned higher than in Lufengosaurus and Plateosaurus
  6. Amphicoelous cervical and dorsal vertebrae with low neural arches and spines, lacking pleurocoels
  7. Four premaxillary teeth, 17-18 maxillary teeth, 21-23 dentary teeth with compact arrangement
  8. Teeth with relatively high spoon-shaped crowns with gently convex labial margin and conspicuous striations
  9. Robust femur with conspicuous sinuous curvature and well-developed fourth trochanter located posterodorsally on midshaft
  10. Short humerus three-fifths femur length, thick, lacking curvature with well-developed medial head

Species

Yimenosaurus youngi Bai et al., 1990

Type species

Named for Yang Zhongjian (known in English as C.C. Young), the founder of Chinese vertebrate paleontology, widely regarded as the father of Chinese paleontology.

Holotype
YXV 8701 , Yuxi Prefectural Committee Office
Material
Damaged skeleton with incomplete skull and mandible; postcranial skeleton includes incomplete atlas, axis, Cv4, Cv8, four medial articulated dorsals, several fragmentary dorsal vertebra, three complete sacrals, medial caudals, anterior haemal arch, relatively complete ilium, pair of ischia, complete femur, and several incomplete ribs.
Horizon
Fengjiahe Formation, Hettangian–Toarcian, Early Jurassic , 201.4–174.7 million years ago
Locality
Jiaojiadian, Yunnan, China

References

  1. Bai, Z.; Yang, J.; Wang, G. (1990). [Yimenosaurus, a new genus of Prosauropoda from Yimen County, Yunnan province]. Yuxiwenbo (Yuxi Culture and Scholarship) 1: 14-23.

    Erected Yimenosaurus and assigned it to Plateosauridae.

    bai1990a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Sauropods. Princeton University Press.

    Treats Yimenosaurus as a plateosaurid of uncertain position.

    jones2026b