Colorado, Utah, Wyoming, Montana, South Dakota, Nebraska, Kansas, Oklahoma, New Mexico, Arizona, United States
One of the world's most productive dinosaur-bearing rock formations, stretching across 1.5 million km² of the western United States. It has produced more named dinosaur species than almost any other formation, including Allosaurus, Stegosaurus, Diplodocus, Brachiosaurus, and Apatosaurus. The sheer density of fossils has made it the foundation of our understanding of Jurassic North America.
The formation accumulated as a sequence of floodplains, river channels, and lake beds during a semi-arid period when the region lay east of a rising mountain chain. Seasonal floods deposited fine sediments that buried carcasses rapidly, enabling exceptional skeletal preservation. Distinct color banding — red, green, and grey mudstones — helps geologists trace the unit across state lines.
Bone hunters first recognized the Morrison's richness during the Bone Wars of the 1870s–1880s, when Othniel Charles Marsh and Edward Drinker Cope raced to name new species. Their field teams at Como Bluff, Wyoming and Canon City, Colorado excavated dozens of skeletons, sometimes destroying specimens to deny them to rivals. Professional excavations have continued uninterrupted ever since, and new species are still being described.
The Morrison Formation spans parts of 13 U.S. states — roughly the size of Western Europe.
The Bone Wars rivalry between Marsh and Cope produced over 130 new dinosaur species, though many were later found to be duplicates or invalid.
Quarry 9 at Dinosaur National Monument contains a cliff face with over 1,500 bones visible in cross-section, left in place for visitors to see.
Morrison sediments preserve not just dinosaurs but also footprints, eggs, and skin impressions of many species.
5 species in our database · sorted by size