for National Geographic News
Bats learned to fly before they developed their internal "sonar" to navigate and catch insects, the most primitive bat fossil ever found shows.
"This new bat [fossil] is clearly a flying animal, but it lacks the features in the skull that we'd expect to see in an echolocating bat," said Nancy Simmons, chair of Vertebrate Zoology at the American Museum of Natural History in New York and co-author of a new study on the fossil.
Echolocation is the radar-like ability of some animals to emit high-pitched sounds, then detect obstacles or prey by listening to the sounds bounce back.
Bats are thought to have evolved from terrestrial mammals, and scientists have long pondered whether they took to the air before or after they could echolocate.
Previously the most primitive bats known were from the early Eocene, about 50 million years ago, and were fully capable of flapping flight.
They also had physical adaptations for echolocation, and a few fossils even have preserved stomach contents that reveal meals of flying insects.
"So we know they were flying animals and [were] probably echolocating and catching flying insects," Simmons said.
But the new species found in Wyoming's fossil-rich Green River formation, Onychonycteris finneyi, is some 52.5 million years old.
Onychonycteris had fully developed, flight-capable wings, but its ear structure shows that it would not have been able to employ modern bats' famous sonar.
(Related news: "Scientists Fill Blanks on Bat Family Tree" [January 27, 2005].)
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