Open Paleo

Xuanhanosaurus

Dong, 1984 SHWEN-HAHN-o-SAWR-us

Named for Xuanhan County in Sichuan, China, where the fossils were recovered, 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

Xuanhanosaurus is a genus of theropod dinosaur that lived during the Middle Jurassic (Bathonian) of the Sichuan Basin, China, around 166 million years ago. This taxon represents one of the various non-coelurosaurian tetanuran taxa found on the Middle Jurassic of the region, uncovered in the Lower Shaximiao Formation. Although it has been known for more than 40 years, this taxon has been the subject of very few studies, although most seem to agree that it is a tetanuran, possibly a basal allosauroid, highlighting the fact that it has a vestigial fourth metacarpal.

Under dispute

Xuanhanosaurus qilixiaensis is weakly constrained — its holotype is a fragmentary postcranium with much missing data. Benson (2010) recovered it as a basal megalosauroid, in the clade that became Piatnitzkysauridae, whereas Carrano and colleagues (2012) recovered it within Metriacanthosauridae among the allosauroids, a result followed by Zou and colleagues (2025) and Jones (2026). Because Piatnitzkysauridae (Megalosauroidea) and Metriacanthosauridae (Allosauroidea) lie in different major tetanuran lineages, Tetanurae is the least-inclusive clade both hypotheses accept.

Diagnosis

  1. Forelimbs relatively well developed with fourth metacarpal retained (primitive characteristic within Megalosauridae)
  2. Forelimbs possess ambulatory function, contrasting with later-stage tyrannosaurids
  3. Well-developed ventral crest on cervical vertebrae, wing-shaped and prominent
  4. Tridactyl manus with stout, short, non-strongly-curved claws
  5. Cervical vertebrae with posterior concavity and undeveloped anterior projection

Species

Xuanhanosaurus qilixiaensis Dong, 1984

Type species

Named for the town of Qilixia in Xuanhan County, Sichuan, China, where the holotype was recovered.

Holotype
IVPP V6729 , Institute of Vertebrate Paleontology and Paleoanthropology
Material
Fragmentary individual: 2 cervical vertebrae, 4 dorsal vertebrae, complete right pectoral girdle, and forelimb of same side.
Horizon
lower Shaximiao Formation, Bajocian–Oxfordian, Middle Jurassic–Late Jurassic , 170.9–154.8 million years ago
Locality
south limb of Qilixia anticline, Sichuan, China

References

  1. Dong, Z. (1984). [A new theropod dinosaur from the Middle Jurassic of Sichuan Basin]. Vertebrata PalAsiatica 22(3): 213-218. dong1984a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Theropods. Princeton University Press.

    Source of the hip height estimate.

    jones2026c
  3. Carrano, M. T.; Benson, R. B. J.; Sampson, S. D. (2012). The phylogeny of Tetanurae (Dinosauria: Theropoda). Journal of Systematic Palaeontology 10(2): 211-300. Informa UK Limited. doi:10.1080/14772019.2011.630927

    Recovered Xuanhanosaurus within Metriacanthosauridae (incertae sedis), among the allosauroids.

    carrano2012a
  4. Zou, Y.; Chen, L.; Wang, T.; Wang, G. F.; Zhang, W. G.; Zhang, X. Q.; Wang, Z. J.; Wu, X. C.; You, H. L. (2025). A new metriacanthosaurid theropod dinosaur from the Middle Jurassic of Yunnan Province, China. PeerJ 13: e19218. PeerJ. doi:10.7717/peerj.19218

    Placed Xuanhanosaurus within Metriacanthosauridae among allosauroids.

    zou2025a
  5. Benson, R. B. J. (2010). A description of Megalosaurus bucklandii (Dinosauria: Theropoda) from the Bathonian of the UK and the relationships of Middle Jurassic theropods. Zoological Journal of the Linnean Society 158(4): 882-935. Oxford University Press (OUP). doi:10.1111/j.1096-3642.2009.00569.x

    Recovered Xuanhanosaurus as a basal megalosauroid, in the clade that became Piatnitzkysauridae.

    benson2010c
  6. Rauhut, O. M.; Hübner, T.; Lanser, K. (2016). A new megalosaurid theropod dinosaur from the late Middle Jurassic (Callovian) of north-western Germany: Implications for theropod evolution and faunal turnover in the Jurassic. Palaeontologia Electronica 19(2): 26A. Coquina Press. doi:10.26879/654

    Wiehenvenator description recovered it as a basal piatnitzkysaurid among megalosauroids

    rauhut2016a