A 52 million-year-old bat seems to have answered a long-standing puzzle: which did bats acquire first, flight or echolocation. “The most primitive bat ever discovered could fly but [could] not navigate by sound,” the New York Times reported.
The newspaper noted that bats, with more than 1,100 species, are the second most numerous mammal, after rodents. Their success “comes in large part from two evolutionary jumps more than 50 million years ago” – they are the only mammals that can fly, and most locate objects with a sort of biological sonar. Most bats emit high-pitched beeps, then pinpoint an object’s location by analyzing the echoes that come bouncing back. Scientists, however, have not been able to confirm which ability came first.
Writing in the journal Nature
, a team led by Nancy B. Simmons of the American Museum of Natural History
in New York described a fossil bat that strongly suggests flight was acquired before sonar.
Two fossils of the species, named Onychonycteridae finneyi, were found in Wyoming and date from roughly the same period (about 52 million years ago) as the previously oldest-known species, which was also found in Wyoming four decades ago, Times reporter Kenneth Chang reported.
But the new species clearly is more primitive, the researchers said. The latest bat has claws at the end of every finger. All bats have a claw on their first finger (the thumb) and some also have a claw on the index finger. But until now, scientists had not seen claws on the other three fingers of any bat, the newspaper said.
This bat also appears to lack the adaptations considered necessary for echolocation, such as an enlarged cochlea, the part of the inner ear that converts sound vibrations into nerve signals. Its skeleton more closely resembles those of today’s Old World fruit bats, which do not echolocate. The primitive features of Onychonycteridae place it close to the base of the bat family tree.
“This discovery basically supports the flight-first hypothesis,” Simmons told the Times.
The eye sockets of both fossils were crushed, so the scientists could not tell whether the bat had the large eyes of many nocturnal animals, although, as the newspaper noted, bats are – and were – not blind, but “can see quite well.”