CASPER — A pair of 52-million-year-old bat skeletons found in a southwestern Wyoming quarry ago are believed to be the oldest such remains ever discovered — and have been identified as members of a previously unknown species. 

A study published recently in the peer-reviewed journal PLOS ONE, authored by a team of U.S. and Dutch researchers, used a number of physical characteristics to distinguish the new species, Icaronycteris gunnelli, from the two other ancient bat species that have already been documented near Kemmerer. 

Bat fossils are rare, even in Wyoming’s fossil-rich Green River Formation, where warm, swampy conditions during the Eocene epoch proved ideal for creating fossils. 

Skeletal fish, though, are found there hundreds — if not thousands — of times more frequently than any mammal. 

“Bat skeletons are small, light and fragile,” making them unlikely candidates for preservation, Tim Rietbergen, a paleontologist at the Naturalis Biodiversity Center in the Netherlands and the study’s lead author, told Smithsonian Magazine. 

Over the past five decades, the study said, the region has produced less than 30 bat fossils. As fossilized bats go, though, that’s still a lot for a single formation. 

“The oldest articulated bats in the fossil record are from here,” Arvid Aase, museum curator at Fossil Butte National Monument and another author of the study, told the Star-Tribune last summer. (“Articulated” refers to fossils that are found with their bones still connected.) 

One member of the new species was buried deeper in the sedimentary rock — meaning it was deposited earlier — than other Green River Formation bat fossils. 

And as a pair, the bats represent “an increase of 50% in the known bat diversity” from the Green River Formation, the study noted. 

Both specimens came from the quarry known as American Fossil, which welcomes researchers and chisel-wielding tourists alike during its dig season in the late spring and summer. 

The quarry typically hosts dozens of amateur fossil hunters each day. Several visitors’ finds have given rise to past studies or wound up in museums. 

“People are paying to have this experience,” Patrick Hogle, American Fossil’s founder, previously told the Star-Tribune. “But they’re also contributing to the scientific knowledge by just opening up rock.”