Ornitholestes
or-nih-THOL-es-teez
"bird robber"
Type species Ornitholestes hermanni
- Lived
- 158 to 143 million years ago, Late Jurassic
- Diet
- Carnivore
- Length
- about 2 m (7 ft)
- Group
- Theropods, Compsognathidae
- Found in
- United States
- Named by
- Osborn 1903
Size comparison
To scale
Scale in meters
Where its fossils were found
The evidence
Today
150 million years ago
Habitat
Rivers crossed the plains of the Morrison Formation in Wyoming. Stegosaurus, Brachiosaurus and Brontosaurus lived in the region.
Field notes
About Ornitholestes
What it was like
Ornitholestes was a small, lightly built theropod with long, grasping hands and sharp, narrow teeth suited to catching small, quick prey such as lizards or insects. It ran on two legs and likely relied on speed and agility rather than size to catch its meals. Ornitholestes grew to about 2 meters (6.6 feet) long, including a long tail that probably helped it balance while running. The type species is Ornitholestes hermanni.
Its world
Ornitholestes lived from about 158 to 143 million years ago, spanning the Late Jurassic into the Early Cretaceous, in what is now the United States. Its fossils come from the Morrison Formation in Wyoming, a rock unit famous for giant dinosaurs such as Stegosaurus, Allosaurus, Brachiosaurus, and Diplodocus. Ornitholestes itself was far too small to challenge animals like these, and probably hunted smaller game instead.
How it was found
Osborn named Ornitholestes in 1903. Two fossil finds are known today. A hand fossil once thought to belong to Ornitholestes is now thought to belong to a different theropod, showing how new discoveries can change what scientists know even about dinosaurs found long ago.
Field gallery
More views of Ornitholestes
Scenes reconstructed from the available fossil evidence.
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Lived alongside
Found in the same rock formations
A rock formation can hold fossils laid down millions of years apart, so not every animal here met Ornitholestes.
The evidence
The science behind Ornitholestes
Which parts of the picture come from its own bones, and which come from its relatives.
From its own fossils
- A partial skeleton preserves a short skull with sharp teeth, slender limbs and a long tail.
- The arm bones and surviving fingers show a grasping hand and an elbow that could fold tightly.
Borrowed from relatives
- Missing parts of the skeleton are restored by comparison with other small theropods such as Coelurus.
- A covering of fine feathers is inferred from feathered coelurosaurs such as Sinosauropteryx.
Still unknown
- Whether it had feathers, and how much of its body they covered.
- Its color.
- Which small animals it ate.
Often drawn wrong
- The nasal horn in older pictures came from a mistaken reconstruction of the skull.
- A hand once assigned to Ornitholestes is now referred to Tanycolagreus.
Discovery timeline
- 1903Named itOsborn
- 2006PostureSENTER
- 2023SkinCullen et al.
Key papers
The research behind what we know of Ornitholestes
Named it
Named a small predator from a partial skeleton with a short head, grasping arms and a long tail.
Ornitholestes hermanni, a new compsognathoid dinosaur from the Upper Jurassic. Bulletin of the American Museum of Natural History 19: 459-464
No link available
Posture
Testing the arm joints showed that Ornitholestes could bend its elbow tightly and curl its fingers to grasp.
FORELIMB FUNCTION IN ORNITHOLESTES HERMANNI OSBORN (DINOSAURIA, THEROPODA). Palaeontology 49: 1029-1034
Read the paper : FORELIMB FUNCTION IN ORNITHOLESTES HERMANNI OSBORN (DINOSAURIA, THEROPODA) (opens in a new tab)Skin
Comparisons of teeth and living reptiles support lips covering the teeth of theropods when their mouths were closed.
Theropod dinosaur facial reconstruction and the importance of soft tissues in paleobiology. Science 379: 1348-1352
Read the paper : Theropod dinosaur facial reconstruction and the importance of soft tissues in paleobiology (opens in a new tab)
Close relatives
Other members of Compsognathidae
Sources: Wikidata