Birds Had Four Wings at the Time of Dinosaurs, Study Shows
At the time of the dinosaurs many species of birds had wings on their legs, a new fossil discovery revealed.
The finding was published Thursday on the journal Science and it resulted from analysis made on 11 bird specimens from China's Shandong Tianyu Museum of Nature. The birds – collected from the Lower Cretaceous Jehol formation in Liaoning, China, from a period about 150 million to 100 million years ago – undoubtedly sported evidences of large leg feathers.
"These features suggest that the metatarsal feathers were aerodynamic in function, providing lift, creating drag, and/or enhancing maneuverability, and thus played a role in flight," the authors wrote.
The prevailing belief among scientists is that birds evolved from other feathered dinosaurs – a 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, which could probably fly. In addition, 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.
And finally, now leg feathers have been discovered in the 11 museum fossils in China. The feathers are stiff and stick straight out from the birds' legs, and have a large enough surface area to be aerodynamic, the researchers say.
"The nature of their biomechanical contribution to flight ability in taxa that possessed them is debated,” the researchers acknowledged. Still, they added, even with the "paucity of data available … the analysis does suggest an interesting evolutionary pattern."
The scientists studied feathers of other birds and nonbird dinosaurs. 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.
"These new fossils fill in many gaps in our view of the early evolution of birds," animal flight expert David Alexander of the University of Kansas, Lawrence, who was not involved in the study, told Science magazine. 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, told Science magazine that the authors 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.