The oldest bat skeletons ever described from Wyoming fossils

Scientists describe a new species of bat based on the oldest bat skeletons ever recovered. The study of extinct bats, which lived in Wyoming about 52 million years ago, supports the idea that bats diversified rapidly over multiple continents during this time. Led by researchers at the American Museum of Natural History and the Center for Natural Biodiversity in the Netherlands, the study is published today in the journal Nature Plus one.

There are more than 1,460 living species of bats in almost every part of the world, except for the polar regions and a few remote islands. In Wyoming’s Green River Formation—a remarkable fossil deposit from the early Eocene period—scientists have unearthed more than 30 bat fossils in the past 60 years, but until now they were thought to represent the same two species.

“Eocene bats have been known from the Green River Formation since the 1960s. Interestingly, however, most specimens that have come out of this formation were identified as representing one species, Icaronycteris, until about 20 years ago, when another species of Bats have been discovered to belong to another genus, said study co-author Nancy Simmons, coordinator in charge of the museum’s Department of Mammalogy, who helped describe this second species in 2008.

In recent years, scientists from the Naturalis Center for Biodiversity have begun to look more closely at Icaronycteris by collecting measurements and other data from museum specimens.

“Palaeontologists have collected several bats that have been identified as Icaronycteris, and we wondered if there were indeed multiple species among these specimens,” said Tim Rietbergen, evolutionary biologist at Naturalis. “Then learning of a new skeleton distracted us.”

The exceptionally well-preserved skeleton was collected by a private collector in 2017 and purchased by the museum. When the researchers compared the fossil to Rietbergen’s expanded data set, it clearly stood out as a new species. A second fossil skeleton discovered in the same quarry in 1994 and in the collections of the Royal Ontario Museum has been identified as this new species. The researchers gave these fossils the species name Icaronycteris gunnelli in honor of Greg Gunnell, a Duke University paleontologist who died in 2017 and made extensive contributions to understanding fossil bats and evolution.

Although there are slightly older fossil bat teeth from Asia, the two I. gunnelli fossils represent the oldest bat skeletons ever found.

“The fossil lake sediments in the Green River Formation are simply amazing because the conditions that created the paper-thin limestone layers also preserved almost everything that settled to the bottom of the lake,” said Arvid Aase, park manager and curator at Fossil Butte National Monument. , in Wyoming. “One of these bat specimens was found lower in section than all the other bats, making this species older than any of the other bat species recovered from this sediment.”

While the skeletons of I. gunnelli are the oldest bat fossils from this site, they are not the most primitive, supporting the idea that Green River bats evolved separately from other Eocene bats around the world.

“This is a step forward in understanding what happened in terms of evolution and diversification in the early days of bats,” Simmons said.