6 Extinct Animals That Used To Call Into Colorado

Colorado has changed dramatically in recent geological eras. A report by CU Boulder even suggests that 500 million years ago, Colorado had a coastal environment, making it a perfect home for a variety of different species.

Today, Colorado remains known for its incredible diversity of species, but here are a few you might not have known about when they once called home the Centennial State.

1. Stegosaurus

Stegosaurus in the swamp

Copyright: CoreyFord. Archive photo. (iStock)

Paleontologists believe Stegosaurus roamed the Centennial State about 155 million years ago.

Stegosaurus was a Jurassic species estimated to be about 30 feet long and 15 feet tall.

The dinosaur is easily identified by the plates on its back. In fact, the word stegosaurus means “bone plates” in Greek, although there is some debate as to the plate’s purpose.

“One theory is that the plates contained blood vessels to regulate body temperature. Another idea is that the display panels were used to attract mates, like colorful feathers on a bird or antlers on a deer,” the National Park Service said in a post on its website.

Stegosaurus thrived so well in Colorado that it was named the state dinosaur in 1982.

2nd alto camel

Camelops was a camel-like herbivorous animal that lived in North America during the Pleistocene.  Photo credit: Corey Ford (iStock).

Camelops was a camel-like herbivorous animal that lived in North America during the Pleistocene. Photo credit: Corey Ford (iStock).

Ancient camels, or camelops, probably called Colorado home 2.6 million years ago. Scientists estimate they were about seven feet tall at the shoulder and weighed about 1,800 pounds.

“Like living camels, cameos had two-toed, hoofed feet and a long neck. Currently, paleontologists cannot determine if cameos had a hump on its back like live bactrian camels and dromedaries,” according to NPS.

In 2021, crews from the Colorado Department of Transportation discovered Camelops fossils while working on the Central 70 Project construction site.

The molar fossil of the camelops hesternus.  Photo credit: Kiewit Infrastructure Co.

The molar fossil of the camelops hesternus. Photo credit: Kiewit Infrastructure Co.

3. Tyrannosaurus Rex

T-Rex skeleton.  Photo credit: LG Photography (iStock).

T-Rex skeleton. Photo credit: LG Photography (iStock).

Fossil evidence suggests that Tyrannosaurus Rex existed in Colorado at some point during the Cretaceous Period. In fact, the first T-Rex fangs were found in 1874 in Golden, Colorado.

Tyrannosaurus Rex literally means “king of the tyrant lizards,” which is an apt name for one of history’s fiercest beasts.

Scientists believe T-Rex was about 38 feet long and weighed up to 10 tons. They had powerful jaws, a keen sense of smell, and were one of the top predators of the time.

4. Ornithomimus

Figures of Ornithomimus

Photo credit: Savany. Archive photo. (iStock)

Ornithomimus fossils were first discovered in Denver in 1889. They lived during the late Cretaceous period and are believed to be one of the fastest dinosaurs ever. They were about six feet tall and about ten feet long from snout to tail.

Ornithomimus means “bird mimic” in Greek, referring to their resemblance to the modern ostrich.

5. Giant Ground Sloth (Megalonyx)

Megalonyx search tree

Photo credit: Tante_Spray. Archive photo. (iStock)

Giant ground sloths lived on Earth about 35 million years ago during the Pleistocene. These massive mammals have been estimated to be around 10 feet in length and weight £2,200 according to NPS.

Giant Ground Sloth fossils were first found in West Virginia in 1797 and later discovered at the Ziegler Reservoir site near Snowmass Village, Colorado.

“Like other ground sloths, the large clawed sloth was slow moving and most likely solitary. Like other ground sloths, Megalonix likely used its large body size and claws to deter predators,” NPS said.

6. American Cheetah

Alert Cheetah Photo Credit: WLDavies (iStock).

Photo credit: WLDavies (iStock).

The American cheetah, sometimes referred to as the “false cheetah,” is actually not related to the animal that roams around the world today, it was just very similar.

With a physique similar to that of the modern cheetah, the American cheetah is believed to be why Colorado remains home to the second fastest mammal on earth – the pronghorn.

Complete skeletal remains of this animal have been found on the continent, with fossils discovered in Colorado.

This animal roamed the area during the Pleistocene, around 12,000 years ago.

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