Open Paleo

Bonapartenykus

Agnolín et al., 2012 bo-nuh-par-toh-ni-kuss

Named after José F. Bonaparte, the prominent Argentine paleontologist, combined with Greek onyx/onykhos (ὄνυξ/ὄνυχος) meaning 'claw'; overall meaning 'José F. Bonaparte's claw'.

72.2–66.0 million years ago Maastrichtian, Late Cretaceous
Late Cretaceous stages

Bonapartenykus is an extinct genus of alvarezsauroid dinosaur that lived during the Late Cretaceous (Campanian-Maastrichtian) of what is now the Allen Formation of the Río Negro Province, Argentina. The genus contains a single species, Bonapartenykus ultimus, known from a partially articulated, incomplete skeleton that was found in close association to two incomplete eggs and several clusters of eggshells belonging to the oogenus Arriagadoolithus. Bonapartenykus was named in 2012. It has an estimated length of 2.5-3.3 m (8.2-10.8 ft) and weight of 43-72 kg (95-159 lb), making it the largest member of the clade Alvarezsauroidea. Additional skeletons referable to this genus have subsequently been described.

Diagnosis

  1. Mid-dorsal vertebrae with spinopostzygapophyseal laminae ending abruptly above the postzygapophyses
  2. Ventral portion of coracoid strongly medially deflected and decorated with delicate but profuse grooves
  3. Fused scapulocoracoids
  4. Scapula with a very wide notch on the posterior margin of the bone
  5. Ilium and pubis fused

Species

Bonapartenykus ultimus Agnolín et al., 2012

Type species

From Latin word meaning 'latest', as it is one of the geologically youngest alvarezsaurids from South America.

Holotype
MPCA-PV 1290 , Museo provincial de Cipolletti "Carlos Ameghino"
Material
Partial skeleton: incomplete mid-dorsal vertebra, nearly complete left scapulocoracoid, incomplete right scapulocoracoid, incomplete left tibia and femur, nearly complete left pubis articulated with incomplete pubic peduncle of ilium, and anterior blade of left ilium
Horizon
upper Allen Formation, Maastrichtian, Late Cretaceous , 72.2–66.0 million years ago
Locality
Salitral Ojo de Agua, Río Negro, Argentina

References

  1. Agnolín, F. L.; Powell, J. E.; Novas, F. E.; Kundrát, M. (2012). New alvarezsaurid (Dinosauria, Theropoda) from uppermost Cretaceous of north-western Patagonia with associated eggs. Cretaceous Research 35: 33-56. Elsevier BV. doi:10.1016/j.cretres.2011.11.014 agnolín2012a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Theropods. Princeton University Press.

    Source of the hip height estimate.

    jones2026c