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Colorado’s prehistoric residents

Museums of natural history from all over the world have much to thank Colorado for providing excellent samples of prehistoric flora and fauna. The region is a literal hotbed of America’s prehistory. Since the middle- to late-1800s up to the present, it continues to generate fossils of entities from a bygone era.

Listed below are just some of Colorado’s prehistoric residents:


Let’s start with Colorado’s official fossil – the Stegosaurus. This herbivorous dinosaur from the late Jurassic period can easily be recognized by two rows of bony plates protruding from its back. There has been much debate on the use of these plates (Experts say these were either for mating purposes or for defense against predators) but all have agreed that these make the animal appear bigger and more formidable than usual.


A very recent find in Denver was identified by paleontologists from the Denver Museum of Nature and Science as the 68-million-year-old remains of an adult Triceratops. Apparently, this famous frilled and horned dinosaur from the Cretaceous period has been all over the area. In fact, even its relative from an earlier era – the Torosaurus –has fossil remnants in Denver.


A large specimen of the Allosaurus can rival the Tyrannosaurus Rex in size and strength. Thus, this massive carnivore was not one to be messed with. It was one of the earliest species discovered – in 1869 – in Colorado’s Morrison Formation. Fossils of its close cousin, the Torvosaurus, were also found in Delta, Colorado.

Tyrannosaurus Rex

Whether one has watched any part of the Jurassic Park franchise or not, they will surely recognize the T. Rex. Of gigantic teeth and almost cartoonish small arms, this popular prehistoric predator also made the Colorado region its hunting ground. Proof of its existence in the area is its teeth fossils found in 1874 in Golden, Colorado.


Discovered in the Denver Formation, the Ornithomimus is an ostrich-like carnivore. It was capable of reaching 30 miles per hour and effectively dodging its contemporary predators – the raptors and T. Rexes. The Ornithomimus was a significant find due to its near-perfect fossilized feathers and skin.


Ornithopods such as Fruitadens, Camptosaurus, Dryosaurus, and Theiophytalia have also been found in Colorado. These mostly bipedal herbivores are believed to have traveled in large herds for safety in numbers. Despite the controversies in sorting out the identification of these birdlike dinosaurs, most experts agree that many of these ornithopods were partially covered in feathers.


This elegant branch of dinosaurs consisted of the long-necked, plant-eating behemoths that sustained themselves by eating around 100 pounds a day. Species of its class are also among Colorado’s prehistoric residents, including the Apatosaurus, Brachiosaurus, and Diplodocus.


A near-complete skeleton of this small, insect-eating mammal was found in Colorado’s Fruita region. It shares half its name with Docofossor, its fellow burrower from prehistoric times. The Fruitafossor’s petite size clearly defies our general perception of dinosaurs as massive beings.


Despite the name resemblance, the Hyaenodon is not related to hyenas. Their only resemblance lies in the shape of some of its teeth. The Hyaenodon was a creodont – a class of prehistoric carnivorous mammals that prospered after the dinosaurs became extinct. Many of its fossils can still be found in Colorado.

Megafauna mammals

After the dinosaurs went extinct, a new batch of prehistoric mammals succeeded them. While smaller in size some of them were still big enough to be described as mammoth. These megafauna mammals found a home in the temperate climate of prehistoric Colorado and left their fossils for us to discover today.

There’s so much about Colorado’s prehistory to discover. If you’re interested in knowing about the area’s rich origins, let me, Anne Dresser Kocur, tell you more about it. Call me at 303.229.6464 or send me a note at adresser(at)livsir(dotted)com.

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