Open Paleo

Xixiasaurus

Lü et al., 2010 SHE-shah-SOR-us /ˌʃiːʃiəˈsɔːrəs/

Named for Xixia County, Henan Province, China, where the holotype was discovered, combined with Greek 'sauros' meaning 'lizard', translatable as 'Henan Xixia lizard'.

89.8–72.2 million years ago Coniacian–Campanian, Late Cretaceous
Late Cretaceous stages

Xixiasaurus is a genus of troodontid dinosaur that lived during the Late Cretaceous Period in what is now China. The only known specimen was discovered in Xixia County, Henan Province, in central China, and became the holotype of the new genus and species Xixiasaurus henanensis in 2010. The names refer to the areas of discovery, and can be translated as "Henan Xixia lizard". The specimen consists of an almost complete skull (except for the hindmost portion), part of the lower jaw, and teeth, as well as a partial right forelimb.

Under dispute

Xixiasaurus is a poorly understood, unserrated-toothed troodontid whose position varies widely across analyses: with Sinovenator and Mei (Turner and colleagues, 2012), near Byronosaurus (Pei and colleagues, 2020), with Zanabazar and Saurornithoides within Troodontinae (Cau and Madzia, 2021), or paired with Sinusonasus (Hartman and colleagues, 2019; Sellés and colleagues, 2021). It is placed at Troodontidae incertae sedis.

Diagnosis

  1. Fewer maxillary teeth (22) than Byronosaurus (>30) and Mei (24)
  2. Distinct opening on the lateral surface of the base of the nasal process of the premaxilla
  3. Rostral end of the upper jaw forming a tapered U-shape in ventral view
  4. Mandibular symphyseal region slightly inflected medially
  5. Unserrated teeth on anterior and posterior carinae, unlike most other troodontids

Species

Xixiasaurus henanensis Lü et al., 2010

Type species

Named for Henan Province, China, where the holotype was discovered in Xixia County.

Holotype
HGM 41HIII-0201 , Henan Geological Museum
Material
A partial skull, an anterior portion of the lower jaw, and central portions of the ulna and radius, and a partial right manus with a complete first digit.
Horizon
Majiacun Formation, Coniacian–Campanian, Late Cretaceous , 89.8–72.2 million years ago
Locality
Songgou, Zhangying, Henan, China

References

  1. Lü, J.; Xu, L.; Liu, Y.; Zhang, X.; Jia, S.; Ji, Q. (2010). A New Troodontid Theropod from the Late Cretaceous of Central China, and the Radiation of Asian Troodontids. Acta Palaeontologica Polonica 55(3): 381-388. Polska Akademia Nauk Instytut Paleobiologii (Institute of Paleobiology, Polish Academy of Sciences). doi:10.4202/app.2009.0047

    Named Xixiasaurus and compared it most closely with Byronosaurus.

    lü2010a
  2. 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

    Paravian phylogeny placing Xixiasaurus variably among troodontid lineages.

    hartman2019a
  3. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Theropods. Princeton University Press.

    Illustrated by E. Viola.

    jones2026c
  4. Turner, A. H.; Makovicky, P. J.; Norell, M. A. (2012). A Review of Dromaeosaurid Systematics and Paravian Phylogeny. Bulletin of the American Museum of Natural History 371: 1-206. doi:10.1206/748.1

    Recovered Xixiasaurus with Sinovenator and Mei.

    turner2012a
  5. Pei, R.; Pittman, M.; Goloboff, P. A.; Dececchi, T. A.; Habib, M. B.; Kaye, T. G.; Larsson, H. C. E.; Norell, M. A.; Brusatte, S. L.; Xu, X. (2020). Potential for Powered Flight Neared by Most Close Avialan Relatives, but Few Crossed Its Thresholds. Current Biology 30(20): 4033-4046.e8. Elsevier BV. doi:10.1016/j.cub.2020.06.105

    Recovered Xixiasaurus with Byronosaurus.

    pei2020a
  6. Cau, A.; Madzia, D. (2021). The phylogenetic affinities and morphological peculiarities of the bird-like dinosaur Borogovia gracilicrus from the Upper Cretaceous of Mongolia. PeerJ 9: e12640. PeerJ. doi:10.7717/peerj.12640

    Recovered Xixiasaurus within Troodontinae, as the sister of Zanabazar plus Saurornithoides.

    cau2021a
  7. Sellés, A. G.; Vila, B.; Brusatte, S. L.; Currie, P. J.; Galobart, À. (2021). A fast-growing basal troodontid (Dinosauria: Theropoda) from the latest Cretaceous of Europe. Scientific Reports 11(1). Springer Science and Business Media LLC. doi:10.1038/s41598-021-83745-5

    Recovered Xixiasaurus as the sister of Sinusonasus.

    sellés2021a