Fossils

Intro

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.

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.

Insects

The Florissant Fossil Beds National Monument protects a site where ash from volcanic eruptions 34 million years ago trapped and preserved an entire ecosystem. Paleontologists have collected more than 60,000 specimens, including 140 plant species and 1,100 insect species. The world’s first roses, flies preserved in such detail that the lenses in each eye can be counted, and massive, petrified redwood stumps may all be found at Florissant.

Dinosaurs

Colorado has supplied dinosaurs to museums all over the world. Indeed, our official state fossil is Stegosaurus. There are many places in the state to view dinosaurs in museums and in the field (Points of Geologic Interest map). It all began in 1870 when a single tail vertebra, the first dinosaur specimen found in western North America, was discovered in Middle Park. A year later, John Wesley Powell, the Grand Canyon explorer and first director of the USGS, remarked on the “reptilian remains” he observed in the area that was later to become Dinosaur National Monument.

Several years later, dinosaur bones were discovered in Garden Park near Cañon City. When word of this discovery spread, the state’s reputation as a repository of world-class specimens solidified. Colorado was suddenly the metaphorical bull’s-eye in the raucous scientific stampede that came to be called the Bone Wars. Eastern museums rushed teams of scientists to Colorado where a fierce battle was joined. Amid rumors and accusations of sabotage, spying, and claim-jumping, competitors scrambled to discover, name, and subsequently cart off the best and biggest skeletons. As a result of all this frenetic activity, dinosaur specimens from Colorado ended up in the museums of Pittsburgh, Cleveland, Chicago, Yale University, and the Smithsonian.

Colorado’s dinosaur fossils cover a wide spectrum—coming from all three periods of the Mesozoic Era—and representing all six dinosaur groups and twelve of the fifteen known dinosaur families. Specimens recovered in the 1800s are still some of the best fossils of two of the groups of dinosaurs.

The first T. Rex fossil in the world was discovered on the flanks of South Table Mountain, and yet, dinosaurs are still being found today. A house foundation in a southern Denver suburb yielded T. Rex bones, a particularly significant find since there are fewer than thirty T. Rex skeletons in the world. During construction of Denver’s new baseball stadium, paleontologists removed a dinosaur rib that was sticking up just behind what is now home plate.

Vertebrates and Invertebrates

In 1887, strata in Garden Park near Cañon City were found to contain the world’s oldest known vertebrates. The area now known as the Indian Springs Trace Fossil Natural Area is also unusually rich in traces of animals that lived 450 million years ago. Study of trace fossils such as the tracks and burrow patterns of horseshoe crabs, brachiopods, and trilobites give clues to the behavior of creatures living in the mudflats of an ancient tidal lagoon.

Our collaborators at the Denver Museum of Nature and Science have generously provided us with a spectacular array of photographs of specimens from their collection. Their paleontological program is active locally and internationally.

Plants

CGS Field Work

Our own field work, depending on the region, routinely turns up ‘regular’ fossils, trace fossils, and other artifacts from early human habitation.