Scientists Uncover Super-Old Fossils In Wyoming — VIDEO

A group of scientists in Wyoming were in for a bit of a surprise when they rappelled into a deep, relatively unexplored cavern in late July. During an excavation of a Wyoming cave, paleontologists discovered the remains of prehistoric animals — and not just any prehistoric animals. The scientists believe the fossils belong to big prehistoric mammals like the North American lion and the American cheetah, which were driven to extinction more than 10,000 years ago.

The excavation of Wyoming's Natural Trap Cave began in late July. The cave, which is located at the base of the Bighorn Mountains near the Montana border, is an 80-foot sinkhole with a a 15-foot-wide entry point, according to the National Park Service. Scientists believe it was a dangerous snare for the mammals who walked the Earth during prehistoric times, causing them to fall in with no way out — hence the name Natural Trap Cave.

In a video uploaded to YouTube on Aug. 5, Australian professor and excavation team member Alan Cooper explained that the Natural Trap Cave is known for being one of leading locations for mammal remains. "This is one of the richest sites for megafauna mammal bones in the lower 48 states and southern Canada," Cooper said in the video.

Australian Centre for Ancient DNA (ACAD) on YouTube

Julie Meachen, a professor at Des Moines University, told CNN that the excavation team had no idea what they were getting into when they entered the Natural Trap Cave. Although the cave was discovered in the 1970s, scientists haven't descended into the deep sinkhole in decades. "We hadn't been there in 30 years and we didn't know what the cave would be like," Meachen said.

Meachen added that the cave acts like a refrigerator to these fossils, which is why the remains are well preserved. According to Reuters, Meachen and her colleagues not only found the remains of the American cheetah and North American lion, but also of bison, horses and gray wolves. She said these animals lived between 12,000 and 23,000 years ago — some thousands of years before the Ice Age began.

According to the National Park Service, more than 30,000 fossils have been removed from the 85-foot sinkhole since the 1970s. In addition to the recent discoveries of cheetah and lion remains, scientists have also uncovered mammoth, bear and even camel fossils from the cavern.

Once this excavation is finished, the scientists will be taking the fossils back to their universities for further research and DNA testing. Cooper said in the video that he and his colleagues will fly some of the remains to Australia in coolers full of ice packs. "We'll try to keep them at refrigerator temperature ... so there's no changes in the material," Cooper said.