Four-Winged Birds Fossils Found In China: Why Did They Go Extinct?
A four-winged bird that existed more than 100 million years ago has been discovered and studied in China.
According to researchers, evidence of large leg feathers were confirmed in 11 of Shandong Tianyu Museum of Nature's prehistoric bird specimens. These large leg feathers suggest that the birds sported wings on their legs, an important stepping stone in the evolution of flight. Specialists reported that the museum's 11 four-winged bird fossils had all been discovered in the Lower Cretaceous Jehol Biota formation located in Liaoning, China. The Lower Cretaceous period marks the fossils at 150 million to 100 million years old.
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Scientists have long believed that birds have evolved from feathered dinosaurs, a theory repeatedly supported by the discovery of prehistoric fossils of feathery birdlike creatures. In 2000, scientists believed they found the missing link when the fossil of a non-avian dinosaur with feathered arms and legs was discovered.
Called the Microraptor, scientists determined that the creature possessed the mechanics that make flight possible. Researchers say the feathers are stiff and stick straight out from the creature's leg. The perpendicular feathers have a surface area large enough to generate aerodynamic lift. However, despite the convincing shape and size of the feathers found on the four-winged bird, researchers debate whether or not these early four-winged birds actually use their legs for flight.
"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."
However, Paleontologist Kevin Padian of the University of California, Berkeley, argued that the feathers do not provide any evidence that it contributes to flight. In fact, Padian believes the feathers might even create drag that would hinder flight. Instead, the birds may have used their plumes for courtship instead, another scientist suggested. If Padian's theory is true, then the four-winged bird would not only be flightless, but will also be highly vulnerable to prey.
Researchers also analyzed the feathers of other birds and nonbird dinosaurs. Scientists reported that feathers that cover the entire leg and feet were first developed in dinosaurs and later continued in early birds. However, the feathers gradually disappeared from their feet and then their legs. Modern flying birds have wings on their arms only.
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