Open Paleo

Xiaosaurus

Dong & Tang, 1983 shyow-SOR-us /ʃaʊˈsɔːrəs/

From Chinese 'xiao' meaning 'dawn', referring to the early geological age of the fossil, combined with Greek 'sauros' meaning 'lizard'.

170.9–154.8 million years ago Bajocian–Oxfordian, Middle Jurassic–Late Jurassic
Middle Jurassic and Late Jurassic stages

Xiaosaurus is a genus of small herbivorous ornithischian dinosaur from the middle Jurassic (approximately 170.3 to 163.5 million years ago) of what is now the Sichuan Basin of China.

Under dispute

Xiaosaurus is a small ornithischian from the Middle Jurassic of China. Long treated as a nomen dubium, it was provisionally accepted as valid by Barrett and colleagues (2005) on a single humeral autapomorphy, a reading later works follow; the type material is of unknown whereabouts, and the fragmentary remains do not support a placement below Ornithischia. It was formerly placed in the deprecated Fabrosauridae.

Diagnosis

  1. Humerus proximally straight, lacking the medial curvature seen in all other basal ornithischians

Species

Xiaosaurus dashanpensis Dong & Tang, 1983

Type species

Named for Dashanpu, the village near Zigong in Sichuan, China, where the holotype was excavated.

Holotype
IVPP V6730A , Institute of Vertebrate Paleontology and Paleoanthropology
Material
A maxilla fragment with one tooth, two cervical and four caudal vertebrae, a humerus, and a complete right hind limb.
Horizon
lower Shaximiao Formation, Bajocian–Oxfordian, Middle Jurassic–Late Jurassic , 170.9–154.8 million years ago
Locality
Dashanpu, Sichuan, China

References

  1. Dong, Z.; Tang, Z. (1983). New ornithopod genus from the Middle Jurassic of Sichuan Basin, China. Vertebrata PalAsiatica 21(2): 168-171. dong1983b
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

    Reports Xiaosaurus as provisionally valid.

    jones2026a
  3. Barrett, P. M.; Butler, R. J.; Knoll, F. (2005). Small-bodied ornithischian dinosaurs from the Middle Jurassic of Sichuan, China. Journal of Vertebrate Paleontology 25(4): 823-834. Informa UK Limited. doi:10.1671/0272-4634(2005)025[0823:sodftm]2.0.co;2

    Emends the diagnosis to a single humeral autapomorphy and provisionally accepts Xiaosaurus as valid.

    barrett2005a
  4. Butler, R. J.; Upchurch, P.; Norman, D. B. (2008). The phylogeny of the ornithischian dinosaurs. Journal of Systematic Palaeontology 6(1): 1-40. doi:10.1017/S1477201907002271

    Accepts the humeral autapomorphy but leaves Xiaosaurus out of its analysis, the type material being of unknown whereabouts.

    butler2008b
  5. Boyd, C. A. (2015). The systematic relationships and biogeographic history of ornithischian dinosaurs. PeerJ 3: e1523. PeerJ. doi:10.7717/peerj.1523

    Treats Xiaosaurus as valid on the humeral autapomorphy but too fragmentary for phylogenetic analysis.

    boyd2015a