Small feather dinosaur glided with biplane wings

Washington, Jan 24: About 125 million years before the Wright brothers embraced a similar design, a small feathered dinosaur took to the air with a biplane wing arrangement enabling it to glide from treetops, experts say.

The discovery of the tree-dwelling Microraptor in China was announced in 2003, but scientists writing this week in the journal Proceedings of the National Academy of Sciences are offering a fundamental reassessment of how it flew.

Microraptor was a type of dinosaur known as a dromaeosaur and may be a relative of early birds. It was about 30 inches long from its head to the end of its lengthy tail, with a light, pigeon-sized body.

Remarkably, it boasted two sets of wings -- on the forelimbs and hind legs -- covered with feathers laid out in a manner similar to birds. It was a glider -- like a flying squirrel -- apparently not capable of true flight.

There has been a long-running debate over the origin of avian flight.

Microraptor lived about 125 million years ago -- roughly 30 million years before the earliest-known bird Archaeopteryx. But Texas Tech University paleontologist Sankar Chatterjee, who led the study, said Microraptor may represent a throwback form that was an intermediate stage in bird evolution.

The Chinese scientists who found Microraptor's beautifully preserved fossil proposed that when it glided between trees, it spread out its legs and kept its wings one behind the other in a tandem pattern much like a dragonfly.

But using computer models and anatomical analysis, Chatterjee and aeronautical engineer Jack Templin found that this dragonfly arrangement would not work. In particular, they looked at the limb joints and feather orientation of Microraptor.

'JUST ONE CHOICE'

''We knew that there was something wrong anatomically,'' Chatterjee said.

''There is just one choice. It has to have this biplane wing design,'' Chatterjee added.

Chatterjee proposed that it positioned its hind legs below its body, adopting a biplane-like arrangement not unlike the one used by two other aviation pioneers -- Orville and Wilbur Wright -- in their Wright Flyer in humankind's first powered flight in 1903 at Kitty Hawk, North Carolina.

A computer flight simulation of Microraptor employing this wing arrangement demonstrated it would undulate up and down, perfect for gliding among trees, and may have been able to glide over a distance of 130 feet.

It is widely believed among paleontologists that the first birds arose from small, feathered dinosaurs.

''Basically what happened is there is a transition from biplane to monoplane,'' Chatterjee said. ''If you look at Archaeopteryx and all other birds, they have this typical monoplane design.'' Another small dinosaur known only from partial remains, Pedopenna, also may have used a biplane gliding approach, he said.

The researchers did acknowledge this biplane design may have been a failed evolutionary experiment that did not lead to birds.

One theory is that birds evolved from little dinosaurs that were running and jumping from the ground. A competing theory is that birds evolved from small dinosaurs living in trees that initially used feathers to control their descent like a parachute, then glided through the forest canopy and eventually flapped their wings to achieve true flight.

''This really settles once and for all that flight really evolved from trees down,'' Chatterjee said.

REUTERS

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