The Scenario

This scene depicts an attack played out in a shallow stream-bed with forested banks, about 140 million years ago in the area that is now Utah, Colorado, and Wyoming. An attacking group of ceratosaurs has isolated an individual camptosaur, in the foreground, as well as a mother and juvenile barosaur, in the background, while the other barosaurs and camptosaurs flee. Also fleeing in the right foreground is a smaller predator, Ornitholestes.

The Environment

Fossils of these dinosaurs are preserved in rocks of the Morrison Formation. These rocks represent the sediments washed out of canyons by the rivers and streams draining the ancestral Rocky Mountains to the west. The sand and mud were deposited across an immense, relatively flat flood-plain that also contained shallow lakes, ponds, and swamps. The larger rivers probably always ran; however, seasonal rainfall dictated that the smaller streams ran only during the wetter seasons, so that parts of the flood plain were actually quite dry during certain times of the year. The flood plain bordered a shallow sea to the east that, from time to time during the Age of Dinosaurs, extended from the Gulf of Mexico up to the Arctic Ocean. The forested areas were populated primarily by conifers, with other plants on the flood plain, including ginkgoes, ferns, and the cycadlike bennetites.