A team of paleontologists has discovered a fossil in northwestern Colorado, revealing a new kind of mammal that lived alongside the dinosaurs.

CU Boulder Professor Jaelyn Eberle and her colleagues discovered a mammal similar to a muskrat that lived in Colorado about 70 to 75 million years ago. It was discovered near Rangely and named Heleocola piceanus. The team's findings were published on Oct. 23.

Even though the animal likely weighed two pounds, it's considered large for a mammal in this period and relatively rare.

"It's quite a bit larger than the mammals that would've been scurrying around at that time," Eberle said.

John Foster, a scientist at the Utah Field House of Natural History State Park Museum, remembers seeing the mammal's jawbone for the first time, protruding from a slab of sandstone in 2016. The fossil measured about an inch long.

"I said, 'Holy cow, that's huge,'" Foster said in a release.

The muskrat was likely a plant-based omnivore, meaning it ate mostly plants with a few insects or other animals. Eberle said as of now, the mammal seems to only be found in Colorado.

"It's great to see it in the news and see a brand new genus of fossil mammal come out of western Colorado," she said.

The Colorado that the mammal lived in 70 million years ago would be unrecognizable today. At that time, it was a marsh and swamp-like land home to turtles, dinosaurs and crocodiles.

"The region might have looked kind of like Louisiana," ReBecca Hunt-Foster, a paleontologist at Dinosaur National Monument in Utah and western Colorado, said in a release. "We see a lot of animals that were living in the water quite happily like sharks, rays and guitarfish."

Most mammals, however, were the size of mice or rats. When examining the teeth of the new mammal, Eberle said they looked similar to an opossum's mouth.

Scientists have less information about the time period in which the newly discovered mammal lived. This is because of a sea wave that covered many parts of western North America, meaning there's less land sediment with fossils in it. This discovery is a new step forward in further understanding that time period.

"Because we don't have this time slice, this 70 to 75 million-year-old time slice represented, it's just not as well known as other slices of late cretaceous time," Eberle said

She said scientists are learning more about the diversity among mammals in this time period than what was known a couple of decades ago. She said it's exciting and cool that Colorado plays a role in it.

"It's important to know if we're going to understand the evolution of mammals, and we are mammals, so then we need to go back ... to understand the roots of kinds of mammals we're living with today," Eberle said.