Tenontosaurus

What it was like

Tenontosaurus was a plant-eating ornithopod that grew to about 7 meters (23 feet) long, with a long, heavy tail that made up much of its body length. Bundles of bony tendons ran along its back and tail, stiffening them and giving the genus its name. It walked mainly on four legs but could likely rear up on two to reach food or watch for danger. Its skull was long and narrow, ending in a horny beak.

Its world

Tenontosaurus lived across the western United States, in places now called Montana, Oklahoma, Wyoming, Texas, Arizona, and Idaho, from about 121 to 94 million years ago. It shared its world with the huge predator Acrocanthosaurus and with Deinonychus, a much smaller but sharp-clawed hunter. Fossils of Tenontosaurus are often found alongside Deinonychus teeth, suggesting the smaller predator regularly fed on it, possibly hunting in groups. Other neighbors included the armored Sauropelta and the small, burrowing Oryctodromeus.

How it was found

Ostrom named Tenontosaurus in 1970, and it has since become one of the most common Early Cretaceous dinosaurs known, with about 70 separate fossil finds recorded. Most come from the Cloverly Formation, though bones have also turned up in the Antlers, Paluxy, and other formations across its range.