Dinosaurs Photo Credit: kbeis (iStock).

Photo Credit: kbeis (iStock).

Colorado has changed dramatically over the last few geologic eras. One report from 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 to thrive. 

Today, Colorado remains known for its incredible range of species, but here are a few that you may not have known once called the Centennial State home.

1. Stegosaurus  

Stegosaurus in Swamp

Photo credit: CoreyFord. File photo. (iStock)

Paleontologists believe that stegosauruses roamed the Centennial State roughly 155 million years ago. 

Stegosauruses were a Jurassic species that are estimated to have been around 30 feet long and 15 feet tall. 

The dinosaur is easily distinguishable by the plates along its back. In fact, the word stegosaurus translates to "bony plates" in Greek, though, there is some debate regarding the purpose of the plates. 

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

Stegosauruses thrived so well in Colorado, it was named the state dinosaur in 1982.

2. Ancient Camel 

Camelops was a camel-type herbivorous animal that lived in North America during the Pleistocene Period. Image Credit: CoreyFord (iStock).

Camelops was a camel-type herbivorous animal that lived in North America during the Pleistocene Period. Image Credit: CoreyFord (iStock).

Ancient Camels, or Camelops, likely called Colorado home starting 2.6 million years ago. Scientists estimate that they were around seven feet tall at the shoulder and weighed around 1,800 pounds. 

"Like living camels, Camelops had two-toed, hooved feet and a long neck. At present, paleontologists are unable to determine if Camelops had a hump on its back like living Bactrian and Dromedary camels," according to NPS.

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

The camelops hesternus molar fossil. Photo Credit: Kiewit Infrastructure Co.

The camelops hesternus molar fossil. 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 at some point during the Cretaceous Period there were Tyrannosaurus Rex in Colorado. In fact, the first ever T-Rex teeth were found in Golden, Colorado in 1874

Tyrannosaurus Rex literally translates to “King of the Tyrant Lizards", which is a fitting names for one of history's most ferocious beasts.

Scientists believe that T-Rex were around 38 feet long, and may have weighed up to 10 tons. They had powerful jaws, a keen sense of smell, and were one of the best predators at the time. 

4. Ornithomimus

Figures of Ornithomimus

Photo credit: Savany. File photo. (iStock)

Ornithomimus fossils were first discovered in 1889 in Denver. They lived during the Late Cretaceous Period and are believed to be one of the fastest dinosaurs that ever existed. They stood at around six feet tall and were around ten feet long from snout to tail. 

Ornithomimus means 'bird mimic' in Greek, which is in reference to their similarities to the modern day ostrich. 

5. Giant Ground Sloth (Megalonyx)

Megalonyx Searching Tree

Photo credit: Aunt_Spray. File photo. (iStock)

Giant Ground Sloths walked the earth around 35 million years ago, during the Pleistocene Era. These massive mammals were estimated to be around 10 feet long and weighed around 2,200 pounds, according to NPS

Giant Ground Sloth fossils were first found in 1797 in West Virginia, and were 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 lived solitarily. Like other ground sloths, Megalonyx probably 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).

Sometimes referred to as a 'false cheetah', the American Cheetah isn't actually related to the animal that's walking the globe today, it was just extremely similar.

With a similar build to the modern cheetah, it's believed that the American Cheetah is the reason Colorado remains home to the second-fastest mammal on the planet – the pronghorn.

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

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

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