Ornitholestes

Ornitholestes is a genus of small theropod dinosaur from the Late Jurassic Morrison Formation of western North America. The genus contains a single named species, Ornitholestes hermanni. It is known from a small number of fossil remains, including the holotype AMNH 5336, collected in the Morrison Formation and described by Henry Fairfield Osborn in 1903. The name means “bird robber,” reflecting its presumed predatory habits.

Anatomy and size: Ornitholestes was a slender, bipedal carnivore, estimated to be about 1.2 to 1.8 meters in length. It possessed a long, relatively low skull with sharp teeth, long forelimbs equipped with grasping hands, and a long, stiff tail. The skeleton indicates a light frame geared toward speed and agility.

Classification and relationships: Ornitholestes is generally regarded as a basal coelurosaur. Earlier classifications placed it among various small “coelurosaur” or “coelurian” families, but more recent analyses place it outside the major later-diverging coelurosaur groups. Its precise position within Coelurosauria remains uncertain.

Paleoecology: In the Late Jurassic Morrison Formation, diverse dinosaur communities existed, including large sauropods and theropods. As a small predator, Ornitholestes would have hunted small vertebrates and possibly insects, occupying a different niche from larger predators of its ecosystem.

Fossil record: Beyond the holotype, only limited material has been referred to Ornitholestes, which constrains detailed reconstructions of its appearance and behavior. The available fossils nonetheless highlight Ornitholestes as an early, small coelurosaur within a dynamic Late Jurassic ecosystem.