Open Paleo

Ornitholestes

Osborn, 1903 or-NITH-o-LES-teez

From Ancient Greek 'ornis' (bird) and 'lestes' (robber); meaning 'bird robber'.

154.8–143.1 million years ago Kimmeridgian–Tithonian, Late Jurassic
Late Jurassic stages

Ornitholestes is a small theropod dinosaur of the late Jurassic (Brushy Basin Member of the Morrison Formation, middle Kimmeridgian age, about 154 million years ago) of Western Laurasia (the area that was to become North America).

Under dispute

The placement of Ornitholestes is unsettled. Most modern analyses recover it at or near the base of Maniraptoromorpha (Hartman and colleagues, 2019), and it has also been proposed as the basalmost oviraptorosaurian (Chapelle and colleagues, 2021). It is not a compsognathid. It is placed conservatively at Coelurosauria incertae sedis pending resolution.

Diagnosis

  1. Distal caudal vertebrae deep and ventrally bifurcated
  2. Pubis bowed, with the distal end directed posteroventrally
  3. Pubic apron lacking a pubic fenestra
  4. Ischium with a broad obturator notch and a triangular obturator process

Species

Ornitholestes hermanni Osborn, 1903

Type species

Named for Adam Hermann, the head preparator at the American Museum of Natural History, who directed the restoration and mounting of the skeleton.

Holotype
AMNH 619 , American Museum of Natural History
Material
Skull with both mandibles; 45 vertebrae (3 cervicals, 11 dorsals, 4 sacrals, 27 caudals); both ischia, left ilium, and both pubes (distal ends missing); incomplete left femur, proximal left fibula, both humeri, right metatarsals II-IV and left metatarsal IV, pedal phalanges and unguals, a right tarsal, and fragmentary metacarpals and manual phalanges.
Horizon
Morrison Formation, Kimmeridgian–Tithonian, Late Jurassic , 154.8–143.1 million years ago
Locality
Bone Cabin Quarry, Wyoming, United States

References

  1. Osborn, H. F. (1903). Ornitholestes hermanni, a new compsognathoid dinosaur from the Upper Jurassic. Bulletin of the American Museum of Natural History 19(12): 459-464. osborn1903a
  2. Ostrom, J. H. (1980). Coelurus and Ornitholestes: Are they the same?. Aspects of Vertebrate History: Essays in Honor of Edwin Harris Colbert (Jacobs, L. L., ed.) 245-256. Museum of Northern Arizona Press.

    Compares the type material of the two genera and concludes they are distinct rather than synonymous.

    ostrom1980a
  3. Carpenter, K.; Miles, C.; Ostrom, J. H.; Cloward, K. (2005). Redescription of the small maniraptoran theropods Ornitholestes and Coelurus from the Upper Jurassic Morrison Formation of Wyoming. The Carnivorous Dinosaurs (Carpenter, K., ed.) 49-71. Indiana University Press, Bloomington.

    Redescribes both genera as distinct taxa and refers the isolated manus previously attributed to Ornitholestes (AMNH 587) to Tanycolagreus.

    carpenter2005b
  4. 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 recovering Ornitholestes near the base of Maniraptoromorpha.

    hartman2019a
  5. Chapelle, K. E.; Norell, M.; Ford, D. P.; Hendrickx, C.; Radermacher, V. J.; Balanoff, A.; Zanno, L. E.; Choiniere, J. N. (2021). A CT-based revised description and phylogenetic analysis of the skull of the basal maniraptoran Ornitholestes hermanni Osborn 1903. Conference Program of the 81st Annual Meeting of the Society of Vertebrate Paleontology.

    Proposed Ornitholestes as the basalmost oviraptorosaurian based on skull CT description

    chapelle2021a
  6. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Theropods. Princeton University Press.

    Illustrated by E. Viola.

    jones2026c