The Dinosaurs and Prehistoric Animals of Colorado

Woman inspects Diplodocus dinosaur skeleton western Colorado

milehightraveler / Getty Images

Like many states in the American West, Colorado is known far and wide for its dinosaur fossils: not quite as many as have been discovered in its adjoining neighbors Utah and Wyoming, but more than enough to keep generations of paleontologists busy. On the following slides, you'll discover the most important dinosaurs and prehistoric animals ever to be discovered in Colorado, ranging from Stegosaurus to Tyrannosaurus Rex.

01
of 09

Stegosaurus

Cast of a Stegosaurus stenops skeleton

EvaK / Wikimedia Commons / CC BY-SA 2.5

Probably the most famous dinosaur ever to hail from Colorado, and the official fossil of the Centennial State, Stegosaurus was named by the American paleontologist Othniel C. Marsh based on bones recovered from Colorado's portion of the Morrison Formation. Not the brightest dinosaur that ever lived--its brain was only about the size of a walnut, unlike most residents of Colorado--Stegosaurus was at least well-armed, with fearsome-looking triangular plates and a spiked "thagomizer" on the end of its tail.

02
of 09

Allosaurus

allosaurus

Bob Ainsworth / Wikimedia Commons / CC BY 2.0

The deadliest meat-eating dinosaur of the late Jurassic period, the type fossil of Allosaurus was discovered in Colorado's Morrison Formation in 1869, and named by Othniel C. Marsh. Since then, unfortunately, neighboring states have stolen Colorado's Mesozoic thunder, as better-preserved Allosaurus specimens were excavated in Utah and Wyoming. Colorado is on a much firmer footing for another theropod closely related to Allosaurus, Torvosaurus, which was discovered near the town of Delta in 1971.

03
of 09

Tyrannosaurus Rex

A tyrannosaurus dinosaur in the natural history museum, NYC

Someone35 / Wikimedia Commons / CC BY-SA 3.0

There's no denying that the most famous fossil specimens of Tyrannosaurus Rex hail from Wyoming and South Dakota. But very few people know that the very first T. Rex fossils (a few scattered teeth) were discovered near Golden, Colorado in 1874. Since then, unfortunately, the T. Rex pickings in Colorado have been comparatively slim; we know this nine-ton killing machine rampaged across the plains and woodlands of the Centennial State, but it simply didn't leave all that much fossil evidence!

04
of 09

Ornithomimus

Ornithomimus life reconstruction

Tom Parker / Wikimedia Commons / CC BY-SA 4.0

Like Stegosaurus and Allosaurus (see previous slides), Ornithomimus was named by the ubiquitous American paleontologist Othniel C. Marsh after the discovery of scattered fossils in Colorado's Denver Formation in the late 19th century. This ostrich-like theropod, which has lent its name to an entire family of ornithomimid ("bird mimic") dinosaurs, may have been capable of galloping at speeds in excess of 30 miles per hour, making it the true Road Runner of late Cretaceous North America.

05
of 09

Various Ornithopods

Dryosaurus, a dinosaur of Colorado

Alina Zienowicz / Wikimedia Commons / CC BY-SA 3.0

Ornithopods--small- to medium-sized, small-brained, and usually bipedal plant-eating dinosaurs--were thick on the ground in Colorado during the Mesozoic Era. The most famous genera discovered in the Centennial State include Fruitadens, Camptosaurus, Dryosaurus and the hard-to-pronounce Theiophytalia (Greek for "garden of the gods"), all of which served as cannon fodder for voracious meat-eating dinosaurs like Allosaurus and Torvosaurus.

06
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Various Sauropods

Brachiosaurus, DinoPark Vyškov

DinoTeam / Wikimedia Commons / CC BY-SA 3.0

Colorado is a big state, so it's only fitting that it was once home to the biggest of all dinosaurs. A huge number of sauropods have been discovered in Colorado, ranging from the familiar Apatosaurus, Brachiosaurus, and Diplodocus to the less-well-known and harder-to-pronounce Haplocanthosaurus and Amphicoelias. (This last plant-eater may or may not have been the biggest dinosaur that ever lived, depending on how it compares to the South American Argentinosaurus.)

07
of 09

Fruitafossor

Fruitafossor, a prehistoric mammal of Colorado

Nobu Tamura / Wikimedia Commons / CC BY 3.0

Paleontologists know more about the six-inch-long Fruitafossor ("digger from Fruita") than just about any other Mesozoic mammal, thanks to the discovery of a near-complete skeleton in the Fruita region of Colorado. To judge by its distinctive anatomy (including long front claws and a pointed snout), the late Jurassic Fruitafossor made its living by digging for termites, and it may have burrowed beneath the ground to escape the notice of large theropod dinosaurs.

08
of 09

Hyaenodon

Hyaenodon

Ryan Somma / Wikimedia Commons / CC BY 2.0

The Eocene equivalent of a wolf, Hyaenodon ("hyena tooth") was a typical creodont, a strange breed of carnivorous mammals that evolved about 10 million years after the dinosaurs went extinct and went kaput themselves about 20 million years ago. (The biggest creodonts, like Sarkastodon, lived in central Asia rather than North America), Fossils of Hyaenodon have been discovered all over the world, but they're particularly abundant in Colorado sediments.

09
of 09

Various Megafauna Mammals

Utah Museum of Natural History Mammoth

Paul Fisk / Wikimedia Commons / CC BY-SA 2.0

Like much else of the U.S., Colorado was high, dry and temperate during most of the Cenozoic Era, making it an ideal home for the megafauna mammals that succeeded the dinosaurs. This state is especially well known for its Columbian Mammoths (a close relative of the more famous Woolly Mammoth), as well as its ancestral bison, horses, and even camels. (Believe it or not, camels evolved in North America before they wound up in the Middle East and Central Asia!)