The discovery of fossils in China with feathers on both their front and hind limbs has given the 'gliding' theory of the origins of flight an enormous boost.

Dr Xing Xu and colleagues from the Institute of Vertebrate Palaeontology and Paleoanthropology at the Chinese Academy of Sciences uncovered six specimens at a well known fossil site in western Liaoning, China. The finding is published today in the British journal Nature.

"Its one of the finds of the century," said Dr Alec Ritchie, a palaeontologist at the Australian Museum in Sydney, which is currently exhibiting a collection of Chinese dinosaurs from the same site, some of which are feathered.

"It's a marvellous discovery, because it fills in yet another gap in the chain of evidence from the ground-living dinosaurs to birds," he told ABC Science Online.

"It appears to come down on one side of the theory that birds started flying by gliding rather than flapping. It confirms it rather nicely," he said.

The fossils, a new species named Microraptor gui, possesses long feathers down to their hind legs. Like flight feathers, they have asymmetrical vanes and are arranged in a pattern similar to wing feathers in modern birds.

Palaeontologists have long argued about the origins of wings and the ability to fly. They have been split between the arboreal - or 'top down' - theory, which argues that tree dwelling creatures began gliding between trees, leading to the development of flight.

The competing cursorial - or 'bottom up' - theory, is that flight evolved in ground-living animals who used precursor wings to power a run up trees and hills.

This latest discovery strongly supports the top down theory. It suggests that basal dromaeosaurid dinosaurs - small, biped feathered animals - were four-winged animals that might have been able to glide, representing an intermediate stage toward the active, flapping-flight stage.

Because the hind limb feathers are long on the new species, it would probably have been very difficult for the dinosaurs to run along the ground. This appears to further undermine the bottom-up theory.

"The evidence of an aerodynamic function of Microraptor's forelimb and leg feathers is excellent," writes Associate Professor Richard Prum of the University of Kansas in an accompanying article. "Asymmetrical feather vanes have long been recognised as indicating aerodynamic function in flight or gliding."

Last week, Nature's U.S. competitor, the journal Science, published the research of Professor Kenneth Dial of the University of Montana which demonstrated support for the competing bottom up theory.

Relying on experimental work, Dial argued that the way small birds run uphill suggests that dinosaurs may have evolved wings for a purpose other than flight. By videotaping young partridges running up a slope, he was able to show that their flapping wings helped propel them up the hill.

The six new basal dromaeosaur fossils were found in 2001 and 2002 in the Lower Cretaceous Jehol Group, in the Chaoyang Basin, located in western Liaoning. The dinosaurs lived about 130 million years ago.

But the new find does not settle the debate, said Ritchie. "It certainly strengthens the gliding theory. But given the range of feathers found in the deposit, it is not beyond the bounds that there were other animals running on the ground that developed another way."

"This must be a nightmare for the Creationists to adapt to," Ritchie added. "Scientists couldn't ask for a better range of characters to illustrate how amazingly adaptable the dinosaur clan was at trying out all sorts of things."

Further study into the morphology of the shoulder and wing anatomy is needed to determine if Microraptor glided or flapped. One of the questions is the how the animal rotated its hind legs to engage the hind wings.

Source of the given news and the copyrights belong to a ABC Online News

Back