Washington, Feb 14 : Based on the discovery of a well-preserved fossil of the most primitive bat species known to date, scientists have determined that the animals evolved the ability to fly before they could echolocate.
Echolocation is a biological sonar used by several mammals like bats to locate, range and identify objects.
The new species, named Onychonycteris finneyi, was unearthed in 2003 in southwestern Wyoming, USA. Dating the rock formation in which the fossil was found put its age at 52 million years.
The well-preserved condition of the new fossil permitted the scientists to take an unprecedented look at the most primitive known member of the order Chiroptera.
"When we first saw it, we knew it was special," said lead author Nancy Simmons of American Museum of Natural History (AMNH). "It's clearly a bat, but unlike any previously known. In many respects it is a missing link between bats and their non-flying ancestors."
According to University of Michigan paleontologist Gregg Gunnell, "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."
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, 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," said Gunnell.
A careful examination of Onychonycteris's physical characteristics revealed several surprising features.
The limb proportions of the animal are 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 the primitive bat may have been a skilled climber.
However, long fingers, a keeled breastbone and other features indicate that the animal could fly under its own power like modern bats.
According to Gunnell, "We don't know what the initial incentive was to take to the air,"
"My thought is that these bats probably were commuters at first - developing the ability to fly allowed them to travel to a particular place to feed, then fly back to their nesting area," he added.
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. Without echolocation, Onychonycteris likely had to make do with visual, olfactory, or passive audio cues to hunt.