The top pelvis is typical for an ornithischian, or "bird-hipped," dinosaur. The bottom is typical for a saurischian, or "lizard-hipped," dinosaur.

Collection of Publications International, Ltd.

ORNITHOLESTES (OR-nith-oh-LEST-ees)

Period: Late Jurassic

Order, Suborder, Family: Saurischia, Theropoda, Coeluridae

Location: North America (United States)

Length: 6 1/2 feet (2 meters)

A crew from the American Museum of Natural History found the first remains of Ornitholestes (or "bird robber") at Bone Cabin Quarry near Medicine Bow, Wyoming, in 1900. It consisted of a skull and partial skeleton. This is the same quarry where workers found Apatosaurus, now mounted in the American Museum of Natural History.

H. F. Osborn briefly described Ornitholestes in 1903. In that paper, he also grouped a partial hand from the same quarry, but not the same animal, in the same genus. The skull is complete, though badly crushed. Serrated teeth line the jaws. The first tooth in the upper jaw is the largest. Ornitholestes may have had a small horn over its nose, but scientists are not sure.

The hands are not complete. If the partial hand of the other animal belongs to the same genus, the first finger was short, and the second and third fingers were much longer. Ornitholestes may have captured and held its prey with its hands. All the fingers had sharp curved claws. The animal probably weighed about 35 pounds.

For many years, scientists thought Ornitholestes and Coelurus were the same genus. In 1980, however, John Ostrom showed that they are not the same. Since the discovery of Ornitholestes in 1900, workers have not found additional skeletons of this animal. It seems Ornitholestes was a rare member of its fauna or it was rarely preserved.