The oldest bat skeletons ever found have been described from Wyoming fossils

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A photo of one of two newly described bat skeletons representing Icaronycteris gunnelli. This specimen, the holotype, is now part of the research collections of the American Museum of Natural History. Credit: Mick Ellison/AMNH

Scientists have described a new species of bat based on the oldest bat skeletons ever recovered. The study of the extinct bat, which lived in Wyoming around 52 million years ago, supports the idea that bats diversified rapidly across multiple continents during this time. Led by researchers from the American Museum of Natural History and the Naturalis Biodiversity Center in the Netherlands, the study is published today in the journal PLOS ONE.

There are over 1,460 living species of bats found 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 early Eocene fossil deposit, scientists have discovered more than 30 bat fossils over the past 60 years, but until now it was thought that ‘they both represented the same two species.

“Eocene bats have been known from the Green River Formation since the 1960s. But interestingly, most specimens that have emerged from this formation have been identified as representing a single species, the Icaronycteris index, until about 20 years ago when a second species of bat belonging to another genus was discovered,” said study co-author Nancy Simmons, curator in charge of the Department of Mammals Museum, which helped describe this second species in 2008. “I always suspected that there must be even more species out there.”

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

“Paleontologists have collected so many bats that have been identified as indexes of Icaronycteris, and we wondered if there were actually multiple species among those specimens,” said Tim Rietbergen, evolutionary biologist at Naturalis. . “Then we learned of a new skeleton that diverted our attention.”

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 large dataset, 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 also been identified as belonging to this new species. The researchers gave these fossils the species name Icaronycteris gunnelli in honor of Gregg Gunnell, a Duke University paleontologist who died in 2017 and made significant contributions to the understanding of fossil bats and evolution. .

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

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

Although 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 in the world.

“It’s a step forward in understanding what happened in terms of evolution and diversity in early bats,” Simmons said.

More information:
Tim B. Rietbergen et al, The Oldest Known Bat Skeletons and Their Implications for Eocene Chiroptera Diversification, PLOS ONE (2023). DOI: 10.1371/journal.pone.0283505

Journal information:

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