Open Paleo

Ceratonykus

Alifanov & Barsbold, 2009 suh-RAH-toe-NY-kus Disputed

From Greek keras/keratos ('horn') + onyx/nykos ('claw'), meaning 'horned claw'.

85.7–83.6 million years ago Santonian, Late Cretaceous
Late Cretaceous stages

Ceratonykus is a monospecific genus of alvarezsaurid dinosaur from Mongolia that lived during the Late Cretaceous (Maastrichtian) in what is now the Baruungoyot Formation. The type and only species, Ceratonykus oculatus, is known from a fragmentary skeleton, including an incomplete skull, of an adult individual. It was named and described in 2009 by Vladimir Alifanov and Rinchen Barsbold. Its describers questioned the traditional placement of alvarezsaurs in Theropoda, instead suggesting they were ornithischians, but this has not been accepted since. Ceratonykus has an estimated length of 75 centimeters (2.46 feet) and weight of 760 grams (1.68 pounds). It has been considered as a possible junior synonym of Parvicursor.

Under dispute

Ceratonykus oculatus is consistently recovered as a parvicursorine alvarezsaurid (Alifanov and Barsbold, 2009; Kubo and colleagues, 2023; Meso and colleagues, 2024). Averianov and Lopatin (2022) argued that it is very similar to Parvicursor remotus and is likely a junior synonym of it; this synonymy is not followed by Kubo and colleagues (2023) or by the reference-work treatment of Jones (2026), which retain both as valid genera.

Diagnosis

  1. Femora strongly curved and nearly half as long as tibiotarsus (shorter than in all other parvicursorids)
  2. Tarsometatarsals 3.5 times as long as third metatarsals (third metatarsals more reduced than in other parvicursorids)
  3. Carpometacarpus bears spike-like bones (interpreted as possible ungual phalanges of additional digits)
  4. Natural endocast lacks vertical flexure at brain floor; optic lobes displaced ventrally; acoustic tubercles unusually wide
  5. Deep proximodorsal notch between second and fourth metatarsals; dorsal and palmar surfaces of these bones ridge-like with deep grooves between them
  6. Frontals each nearly four times as long as wide; narrowing rostrally into a narrow wedge; prefrontals adjoining each other medially

Species

Ceratonykus oculatus Alifanov & Barsbold, 2009 Disputed

Type species

From Latin word meaning 'sharp-sighted' or 'big-eyed', in reference to the large orbits of the skull.

Holotype
MPC 100/124 , Paleontological Center, Mongolian Academy of Sciences
Material
Incomplete skull with incomplete lower jaw, several cervical and caudal vertebrae, sternum, right and left coracoids, right humeral fragment, distal forelimb elements, fragmentary ilium, and hind limbs.
Horizon
Baruungoyot Formation, Santonian, Late Cretaceous , 85.7–83.6 million years ago
Locality
Hermiin Tsav, Ömnögovi, Mongolia Alifanov and Barsbold (2009) give the horizon as "Upper Cretaceous, ?Lower Santonian, Baruungoyot Formation".

References

  1. Alifanov, V. R.; Barsbold, R. (2009). Ceratonykus oculatus gen. et sp. nov., a new dinosaur (?Theropoda, Alvarezsauria) from the Late Cretaceous of Mongolia. Paleontological Journal 43(1): 94-106. Pleiades Publishing Ltd. doi:10.1134/s0031030109010109 alifanov2009a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Theropods. Princeton University Press.

    Source of the hip height estimate.

    jones2026c
  3. Kubo, K.; Kobayashi, Y.; Chinzorig, T.; Tsogtbaatar, K. (2023). A new alvarezsaurid dinosaur (Theropoda, Alvarezsauria) from the Upper Cretaceous Baruungoyot Formation of Mongolia provides insights for bird-like sleeping behavior in non-avian dinosaurs. PLOS ONE 18(11): e0293801. Public Library of Science (PLoS). doi:10.1371/journal.pone.0293801

    New alvarezsaurid description's analysis recovered Ceratonykus as a parvicursorine.

    kubo2023a
  4. Averianov, A. O.; Lopatin, A. V. (2022). A new alvarezsaurid theropod dinosaur from the Upper Cretaceous of Gobi Desert, Mongolia. Cretaceous Research 135. Elsevier BV. doi:10.1016/j.cretres.2022.105168

    Argued Ceratonykus is very similar to Parvicursor remotus and likely its junior synonym.

    averianov2022a
  5. Meso, J. G.; Pol, D.; Chiappe, L.; Qin, Z.; Díaz-Martínez, I.; Gianechini, F.; Apesteguía, S.; Makovicky, P. J.; Pittman, M. (2024). Body size and evolutionary rate analyses reveal complex evolutionary history of Alvarezsauria. Cladistics 41(2): 135-155. Wiley. doi:10.1111/cla.12600

    Included Ceratonykus in its alvarezsaur analysis.

    meso2024a