The oldest known bat skeletons shed light on the evolution of flying mammals

WASHINGTON, April 13 (Reuters) – The two oldest known fossil bat skeletons discovered in southwestern Wyoming and dating back at least 52 million years provide insight into the early evolution of this flying mammal — today represented by more than 1,400. Classify .

The fossils, described in a new study, are from a previously unknown species called Icaronycteris gunnelli that is closely related to two other species known from slightly smaller fossils from the same area, which during the Eocene was a humid, subtropical ecosystem centered on a freshwater lake.

“This bat wasn’t much different from the insectivorous bats that fly today,” said paleontologist Tim Rietbergen of the Naturalis Center for Biodiversity in the Netherlands, lead author of the study published this week in the journal Nature. Plus one.

“If it folded its wings next to its body, it would be easy to get it inside your hand. Its wings were relatively short and broad, reflecting a more flapping style of flight. The dentition(s) clearly show that this was an insectivorous bat and that it was likely a wobbling bat,” Rittbergen added. Echo is a form of sonar common to bats, used for navigation and hunting.

Its teeth had sharp cusps and lists for slicing through the exoskeleton of insects and lacked the rounded crushing surfaces useful for eating fruit.

What sets these two fossils apart — one was discovered in 2017 and the other originally in 1994 and only now identified as a new species — is how it showed that bats early in their history already possessed many of the traits seen in modern species.

“Bats have looked a lot like bats since they first appeared as complete skeletons in the fossil record. We don’t have anything we can say they looked ‘half-bat’—or, in other words, we lack any good transitional fossils,” said scientist Matt Jones. Arizona State University paleontologist and co-author of the study.

“Icaronycteris gunnelli is a little different from modern bats – it has longer legs and its arm bones are slightly different in length. Most notably it still retains a claw on its index finger. There are a few other fossil species around this time that claw is still there, but it has been lost in most living bats.

This species was closely related to two other bat species whose fossils were previously found in the same place – Icaronycteris pointer and Onychonycteris finneyi. This indicates that there was greater species diversity earlier in the history of bats than previously expected.

The fossils represent the oldest known bat skeletons – either complete or well preserved. The only ancient bat fossils are isolated teeth and jaw fragments from places like Portugal and China, dating from about 55 to 56 million years ago.

“The early evolutionary history of bats is unclear and we don’t have answers to many questions,” said Rittbergen.

The fact that the oldest known skeletal specimens are clearly fully formed bats indicates that the first bats arose millions of years ago.

“They likely evolved during the Paleocene, which is the 10-million-year period between the end of the Mesozoic and the Eocene,” Jones said, describing a period of amazing evolutionary experimentation in which mammals became the dominant terrestrial animals in the aftermath. The asteroid collision that wiped out the dinosaurs 66 million years ago.

Two other vertebrate groups have achieved powerful flight—the flying reptiles called pterosaurs and birds, both of which appear before bats. The asteroid destroyed the pterosaurs.

Scientists are still trying to determine which mammals were the ancestors of bats.

“We think bats may have evolved from a small, tree-dwelling, insectivorous mammal,” Jones said. “But there are a number of enigmatic fossil insects that date back to the time when bats were evolving, and it is unclear which, if any, of them are related to bats.”

(Reporting by Will Dunham; Editing by Rosalba O’Brien)

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