Saturday, 16 March 2013

Study suggest Early Birds Sported 4 Wings

More than 100 million years ago, birds living in what is now China sported wings on their legs, a new study of fossils suggests. Researchers have discovered an evidence of large leg feathers in 11 bird specimens from China's Shandong Tianyu Museum of Nature. The feathers suggest that early birds had four wings, which may have played a role in the evolution of flight, scientists report in a study.

Birds evolved from other feathered dinosaurs; this belief is supported by discoveries of fossils of feathery birdlike creatures. In 2000, scientists discovered a nonavian dinosaur with feathers on its arms and legs, called Microraptor. Specimens of Archaeopteryx, a transitional fossil between modern birds and feathered dinosaurs, show faint featherlike structures on their legs, but the signs are poorly preserved.

Leg feathers have been spotted in the 11 museum fossils that had been collected from the Lower Cretaceous Jehol formation in China, from a period about 150 million to 100 million years ago. The feathers are stiff and stick straight out from the birds' legs, and have a large enough surface area to be aerodynamic. The fossils belong to at least four different groups, including the genera Sapeornis, Yanornis, Confuciusornis and the Enantiornithes group. The findings suggest that leg feathers weren't just an evolutionary rarity.

Feathers of other birds and nonbird dinosaurs were also analysed. Feathers covering the entire leg and feet first developed in dinosaurs, continued in early birds and later disappeared, the results imply. Birds gradually lost feathers on their feet and then their legs, and today, modern birds have wings on their arms only. Whether these early birds used their leg feathers to fly, and how they may have done so, is still to debate. The flat surface formed by the stiff perpendicular feathers could have provided lift and maneuverability. 

"These new fossils in many gaps in our view of the early evolution of birds," animal flight expert David Alexander of the University of Kansas, Lawrence said. Alexander agrees that the feathers probably had some aerodynamic function, "although whether as stabilizers, steering vanes, or full-blown wings remains to be seen."

Other scientists aren't convinced. Paleontologist Kevin Padian of the University of California, Berkeley said that the study don't provide evidence that the feathers contributed to any sort of flight. In fact, the feathers would create drag that would hinder flight, Padian said. The birds may have used their plumes for courtship instead, another scientist suggested. More studies are needed to nail down the feathers' function. Examining more fossils from the thousands in the museum collection will help, the study's authors say.

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