Utah: Allosaurus (state fossil)
Utah: Allosaurus (state fossil)
The Morrison Formation is famous for its dinosaurs, and is widely exposed in the western states, especially in Utah. These sediments represent a lowland plains environment dotted with lakes and streams, and were formed during the Late Jurassic Period, around 156 - 145 million years ago. At that time, the Ancestral Rockies were worn down to low hills, and the present Rocky Mountains had yet to form.
One of the most famous and popular dinosaurs found in the Morrison is the state fossil of Utah, the theropod Allosaurus. Every dinosaur enthusiast is familiar with Allosaurus, a fierce carnivore that was around 30 - 40 feet long and weighed around 15 tons. Many scientists believe that Allosaurus preyed on the large sauropods that shared its habitat, such as Apatosaurus and Diplodocus. It grasped these animals with its strong, three-fingered hands and dispatched them with quick bites of its powerful jaws.
Although fragmentary bones of Allosaurus were reported as early as 1869, the first nearly complete specimen was found in 1883 by M. P. Felch in Colorado. However, in 1927, a sheepherder stumbled upon a concentration of bones in eastern Utah that eclipsed all previous finds. Over 500 bones were excavated during the first field season alone! The area became known as the Cleveland-Lloyd Dinosaur Quarry, and to date has yielded over 15,000 bones representing individuals of Allosaurus, Stegosaurus, Camptosaurus, and Ceratosaurus, among others. It is still a working quarry, and can be visited by interested persons today.
One of the Cleveland-Lloyd paleontologists, James Madsen, proposed that Allosaurus be given the title of Utah state fossil. The Division of State History ran a contest at the Utah State Fair, inviting children to cast their ballots for their favorite candidate, and Allosaurus won. Later, in 1988, the state legislature passed a bill making it official.
For further information:
Jurassic Morrison Formation Ecosystem