Onychonycteris finneyi, a well-preserved fossil of the most primitive bat species known to date, has shed a new light into the evolution of these mammals.

After examining the fossil, the University of Michigan paleontologist Gregg Gunnell and the researchers from the American Museum of Natural History (AMNH) in New York, the Royal Ontario Museum in Canada and the Senckenberg Research Institute in Germany concluded

that the animals evolved the ability to fly before they could echolocate.

Echolocation, the ability to locate objects and directions by using sounds, it can be found in several mammals such as dolphins, shrews and it was first described for bats.   

"There has been a longstanding debate about how bats evolved, centering around the development of flight and the development of the sonar system they use to navigate and hunt for prey," said Gunnell.

"The three main theories have been that they developed the two abilities together, that flight came first, or that sonar came first. Based on the specimen described in this paper, we were able to determine that this particular animal was not capable of echolocating, which then suggests that bats flew before they developed their echolocation ability."

Despite Onychonycteris's resemblance to animals that came after it, its skull lacks features in and around the ear seen in bats that use echolocation to navigate and hunt.

The findings were published in the latest issue of the journal Nature. Also, the examination of Onychonycteris finneyi, which was unearthed in 2003 in southwestern Wyoming, provided other interesting details.

The fossil, that is 52 million years-old, had claws on all five of its fingers, whereas modern bats have, at most, claws on only two digits of each hand. The limb proportions of Onychonycteris are also different from all other bats-the hind legs are longer and the forearm shorter-and more similar to those of climbing mammals that hang under branches, such as sloths and gibbons. The fossil's limb form and the appearance of claws on all the fingers suggest that Onychonycteris may have been a skilled climber.

In addition, it seems like due to its short wings, Onychonycteris could not fly as far or as fast as most bats that came after it. Instead of flapping its wings continuously while flying it may have alternated flapping and gliding while in the air.

"It finally gives us an answer," lead author Nancy Simmons of AMNH said. "Flying evolved first, echolocation second."

Image credit & copyright: American Museum of Natural History