The hind wings were positioned bellow the fore wings

Jan 24, 2007 08:50 GMT  ·  By

There is a long debate in the scientific world if the first birds flew with 4 wings, after the discovery in 2003 of four-winged dinosaurs, weighing one kilogram, aged 125 million years, in China.

The study comes with a detailed argument for the biplane scenario. Now, a biplane scenario is strongly supported by Sankar Chatterjee of Texas Tech University and his Canadian collaborator, R. Jack Templin. That means Microraptor gui - one of the newly discovered dinosaurs - employed the two upper wings as well as two lower wings in an aerodynamic design similar to the biplanes of the early XXth century.

This design was overpassed in human technology and it is not seen in current birds, that's why scientists are puzzled if this pattern was a phase on the way to the modern birds or just a blind path, checked and discarded by nature.

The discoverer of the Microraptor, Xing Xu of the Chinese Academy of Sciences, imagined that the dinosaur glided, extending its hind legs backward, which is a wings pattern like that seen in dragonflies.

But the new research pointed to the fact that the feathers on the legs were not faced forward, thus if the wing pairs had been set directly one behind the other, they would have been aerodynamically inefficient.

More likely, the legs must have been positioned below the body in flight, resulting two staggered wing planes, the upper one slightly above the lower one. "One other flying dinosaur, Pedopenna, also had feathers on its legs and modern raptors such as falcons have short feathers on their upper legs that reduce air resistance as they fly", said Chatterjee. "Aircraft designers have mimicked many of nature's flight 'inventions,' usually inadvertently," Chatterjee wrote. "Now, it seems likely that Microraptor invented the biplane 125 million years before the Wright 1903 Flyer."

Xu regards the biplane theory "likely," but says that "we really need to work painstakingly to check all details and have an accurate reconstruction, and then we can compare different models in computer or even in wind tunnel, which we are planning to do."

"Microraptor is a critical species in understanding the origin of flight," added Xu.

"The question focuses on what the legs can do, and it's a difficult problem because the fossils are flat and require interpretation as to what they would have looked like in three dimensions", said Matthew Carrano, curator of dinosaurs at the Smithsonian's National Museum of Natural History.

"This creature was probably a side branch rather than a stage evolution had to pass through on the way to today's birds. It's difficult to see how this animal does anything well, it seems so ungainly," Carrano said.

"It forces us to think creatively because it's so far off the beaten path. There are often such experiments that fall by the wayside", he said.

"The important thing is, because we've now got all these feathered dinosaurs to look at, it has kind of opened the gates a bit to speculating about how flight evolved," Carrano said.

Image credit: Proceedings of the National Academy of Sciences