Stegosaurus (foreground) and Allosaurus in the Prehistoric Journey Exhibit, Denver Museum of Nature and Science, Denver, Colorado. Photo credit: Richard M. Wicker for the DMNS.


Despite 150 years of enthusiastic collecting in the state and the fact that Colorado fossils have enriched museums around the world for that same time-span—it is impressive that important fossil discoveries continue to be made. In the past thirty years, scientists have unearthed the world’s first articulated Stegosaurus skeleton; three of the world’s four largest dinosaurs; the largest dinosaur trackway in North America; a huge palm forest; one of the world’s most diverse leaf fossil sites; an eight-foot long mammoth tusk; and Tyrannosaurus rex bones. In 2010 a marvelous treasure trove of ice-age mammals and plants above Snowmass Village in Pitkin County was discovered and subsequently excavated by our colleagues at the Denver Museum of Nature & Science.

Excavating Pleistocene megafauna at the "Snow Mastodon" site in Pitkin County in 2011. Photo credit: VInce Matthews for the CGS.
Excavating Pleistocene megafauna at the “Snow Mastodon” site in Pitkin County in 2011. Photo credit: Vince Matthews for the CGS.

Notable Fossil Rock Units

Three rock units exposed in Colorado are world famous for their treasure troves of fossils: the White River Formation in northeastern Colorado, the Green River Formation in the northwestern part of the state, and the Morrison Formation found in numerous locations around the state. The White River Formation is one of the richest fossil mammal beds in the world, containing fossils of camels, elephants, horses, mammoths, hippos, and rhinoceroses. The famous Green River Formation contains beautiful fossils of fish, scorpions, beetles, frogs, hundreds of insect species, and more than 100 species of trees. The several-hundred-foot-thick layers of the Morrison Formation yield dinosaur bones and tracks including the world’s largest and smallest dinosaurs.