Open Paleo

Xixianykus

Xu et al., 2010 shee-SHYAH-NY-kus

From Xixia County, Henan Province, China (where the fossil was found) and Greek onyx ('claw'), meaning 'Xixia claw'

89.8–83.6 million years ago Coniacian–Santonian, Late Cretaceous
Late Cretaceous stages

Xixianykus is a genus of alvarezsaurid theropod dinosaur known from a slab of rock which contains a partial postcranial skeleton unearthed in the Late Cretaceous (Coniacian-Santonian) Majiacun Formation of the Xixia Basin in Henan, China.

Diagnosis

  1. Sacral rib-transverse process complexes and zygapophyses fused to form separate anterior and posterior laminae
  2. Distinct fossa dorsal to antitrochanter on lateral surface of ilium
  3. Short ridge along posterior surface of pubic shaft near proximal end
  4. Distinct depression on lateral surface of ischium near proximal end
  5. Sharp groove along posterior surface of ischium
  6. Distal end of femur with transversely narrow ectocondylar tuber extending proximally as sharp ridge
  7. Transversely narrow tibial cnemial crest with sharp, ridge-like distal half
  8. Lateral margin of tibiotarsus forms step near distal end
  9. Fibula with substantial extension of proximal articular surface onto posterior face of shaft
  10. Distal tarsals and metatarsals co-ossified to form tarsometatarsus
  11. Sharp flange along anteromedial margin of metatarsal IV near proximal end

Species

Xixianykus zhangi Xu et al., 2010

Type species

Named for Zhang Xinglao, honored in the species description.

Holotype
XMDFEC V0011 , Xixia Museum of Dinosaur Fossil Eggs of China
Material
Partial, articulated postcranial skeleton including five posterior dorsal vertebrae, a complete synsacrum, two anterior caudal vertebrae, dorsal ribs and gastralia, both ilia, right pubis and ischium, and most of the right hindlimb (femoral length 70 mm)
Horizon
Majiacun Formation, Coniacian–Santonian, Late Cretaceous , 89.8–83.6 million years ago
Locality
Zhoujiagou, Yangcheng, Henan, China

References

  1. Xu, X.; Wang, De-Y.; Sullivan, C.; Hone, D. W. E.; Han, F. L.; Yan, R. H.; Du, F. M. (2010). A basal parvicursorine (Theropoda: Alvarezsauridae) from the Upper Cretaceous of China. Zootaxa 2413(1). Magnolia Press. doi:10.11646/zootaxa.2413.1.1 xu2010a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Theropods. Princeton University Press.

    Source of the hip height estimate.

    jones2026c