By Laura Zuckerman

(Reuters) - Scientists excavating an ancient Wyoming sinkhole containing a rare trove of fossils of Ice Age mammals have unearthed hundreds of bones of such prehistoric animals as American cheetahs, a paleontologist said on Friday.

The two-week dig by an international team of researchers led by Des Moines University paleontologist Julie Meachen marked the first exploration of Natural Trap Cave at the base of the Bighorn Mountains in north-central Wyoming since its initial discovery in the 1970s.

Meachen said the extensive excavation that began late last month uncovered roughly 200 large bones of animals like horses that roamed North America from 12,000 to 23,000 years ago and an uncounted number of microfossils of creatures such as birds, lizards and snakes.

“We found evidence of bison, a bit of gray wolf and quite a lot of cheetah and horse,” she said of the first of three planned annual digs, which ended on Friday.

Researchers expect their study of the fossils to provide new insights into the climate, diets and genetic diversity of North American creatures that disappeared during the Ice Age extinction more than 10,000 years ago.

A number of animals that fell 85 feet to their deaths after stumbling into the 15-foot-wide mouth of the cavern were unusually well preserved by cold and damp conditions, Meachen said.

“Some bones still have collagen with intact DNA for genetic testing and some fossils are fragments crushed by rocks. But we take it for what it is when we find it,” she said.

Meachen rappelled 10 times into the sinkhole, which widens to 120 feet at its base, and ascended with the use of ropes that also were used to haul out buckets of artifacts.

The opening of the cave, formed by the collapse of limestone bedrock, has been covered for decades by a metal grate installed by federal land managers.

A pack rat fell into the cavern and died during the excavation but a deer mouse that plunged below ground survived and was sent by bucket to the surface and nursed back to health, Meachen said.

The carcass of the pack rat was left in the sinkhole to be studied over time as a measure of the decay rate of mammals in the cave, she said.

(Reporting by Laura Zuckerman in Salmon, Idaho; Editing by Cynthia Johnston and Eric Beech)