Wyoming's Prehistoric Wildlife
Greybull rest stop northwest of Greybull

The Big Horn Basin is famous for its dinosaur discoveries. During the 1930’s, some of the world’s significant dinosaur fossils were excavated by the American Museum of Natural History. The Basin received renewed interest in the early 1990’s with the discovery of the world’s most complete skeleton of an Allosaurus fragilis, a meat-eating dinosaur of the Jurassic Period (150 million years ago). The largest carnivorous dinosaur of its time, allosaurs stood 10 feet high and measured 35 feet in length. Dinosaur excavations continue today.

The Big Horn Basin also yields animal remains from recent times. Natural Trap Cave on the west slope of the Big Horn Mountains is an ancient sinkhole in the limestone where, for more than 20,000 years, animals fell 80 feet to their deaths. The bottom of the cave is littered with bones of extinct mammals such as mammoths, short-faced bears, saber-toothed cats. American lions and dire wolves.

Scientists study bones and fossils of the Big Horn Basin to help determine past climatic and enveronmental conditions. By researching the earth’s past, scientists can better predict and evaluate future global changes and their effects on wildlife and humans.