Dryosaurus

What it was like

Dryosaurus was a small, fast-moving plant eater that walked and ran on two long, slender legs. It grew to roughly 4 meters (13 feet) long, with a toothless beak at the front of its jaws for cropping plants and ridged cheek teeth farther back for grinding them.

Its build, long legs, a stiff tail held out for balance, and a light frame, suggests speed was its main defense against the large predators that shared its world.

Its world

Dryosaurus lived from about 155 to 143 million years ago, spanning the end of the Late Jurassic and the start of the Early Cretaceous, in what is now the western United States, with likely finds also reported from France. Its bones come from the Morrison Formation in Utah, Wyoming, and Colorado, and from the Marnes de Bléville in France.

It shared the Morrison ecosystem with some of the best known dinosaurs of the Jurassic, including Stegosaurus, Allosaurus, Brachiosaurus, Diplodocus, and Apatosaurus. About 20 fossil finds of Dryosaurus are known, making it one of the better represented ornithopods of its time.

How it was found

Marsh named Dryosaurus in 1894 from Morrison Formation bones found in the western United States. Its closest relatives include Dysalotosaurus, Valdosaurus, Elrhazosaurus, and Eousdryosaurus, and for a time some of these were even classified as species of Dryosaurus itself before being recognized as separate genera. The many Dryosaurus finds since have made it one of the better studied small ornithopods of the Jurassic.