Open Paleo

Hesperonychus

Longrich & Currie, 2009 hes-puh-ruh-NIE-kus

From Greek 'hesperos' meaning 'western' and 'onychos' meaning 'claw'. The type species, H. elizabethae, was named in honor of Dr. Elizabeth Nicholls of the Royal Tyrrell Museum of Palaeontology.

83.6–72.2 million years ago Campanian, Late Cretaceous
Late Cretaceous stages

Hesperonychus is a genus of small dromaeosaurid dinosaur. There is one described species, Hesperonychus elizabethae. The type species was named in honor of Dr. Elizabeth Nicholls of the Royal Tyrrell Museum of Palaeontology who collected it as a student in 1982. It is known from fossils recovered from the Dinosaur Park Formation and possibly from the uppermost strata of the Oldman Formation of Alberta, dating to the Campanian stage of the Late Cretaceous around 75 million years ago.

Under dispute

Hesperonychus is generally recovered as a microraptorine (Longrich and Currie, 2009), extending the group into the Late Cretaceous of North America, the placement followed. Hartman and colleagues (2019), however, recovered the holotype as an avialan at least as close to birds as Balaur. It is placed in Microraptorinae following the prevailing view.

Diagnosis

  1. Pubic peduncle of ilium with medial surface deeply excavated
  2. Posterior wing of ilium with medial shelf split to form anterior and posterior processes
  3. Lateral tubercles of pubis wing-like and curving anteriorly
  4. Pubis with fossa on lateral surface ventral to acetabulum
  5. Pubic apron shifted onto posterior surface of pubis
  6. Pubic symphysis teardrop-shaped in lateral view
  7. Ischiadic process of pubis reduced to narrow lamina
  8. Acetabulum opens dorsolaterally rather than laterally
  9. Pubic shaft sharply curves posteriorly as in Microraptor and Sinornithosaurus
  10. Lateral process of pubis wing-like and curving anteriorly

Species

Hesperonychus elizabethae Longrich & Currie, 2009

Type species

Named for Dr. Elizabeth Nicholls of the Royal Tyrrell Museum of Palaeontology, who collected the holotype specimen as a student in 1982.

Holotype
UALVP 48778 , University of Alberta Laboratory for Vertebrate Paleontology
Material
Partial pelvic girdle comprising the pubes and ilia, from an animal weighing ~1,900g.
Horizon
Dinosaur Park Formation, Campanian, Late Cretaceous , 83.6–72.2 million years ago
Locality
south side of the Red Deer River, approximately 20 km east of Dinosaur Provincial Park, Alberta, Canada Longrich and Currie (2009) place the holotype by bearing and name the Irvine site only for referred pedal phalanges.

References

  1. Longrich, N. R.; Currie, P. J. (2009). A microraptorine (Dinosauria-Dromaeosauridae) from the Late Cretaceous of North America. Proceedings of the National Academy of Sciences 106(13): 5002-5007. Proceedings of the National Academy of Sciences. doi:10.1073/pnas.0811664106 longrich2009a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Theropods. Princeton University Press.

    Source of the hip height estimate, and the appearance features.

    jones2026c
  3. 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

    Recovered the Hesperonychus holotype as an avialan close to birds.

    hartman2019a