Fossil hunters in China have discovered what may be one of the weirdest prehistoric species ever seen -- a four-winged dinosaur that apparently glided from tree to tree.
The 128-million-year-old animal -- called Microraptor gui, in honor of Chinese paleontologist Gu Zhiwei -- was about 2 1/2 feet long and had two sets of feathered wings, with one set on its forelimbs and the other on its hind legs.
Exactly where the creature fits into the evolution of birds and dinosaurs is not clear. But researchers speculated that it developed around the same time as or even later than the first two-wing, birdlike dinosaur, Archaeopteryx, which is believed to have flown by actually flapping its wings.
Paleontologists were intrigued by the discovery. They have seen gliding dinosaurs before, but never one with feathers. And they have never seen a four-winged dinosaur before.
"It would be a total oddity -- the weirdest creature in the world of dinosaurs and birds," said Luis Chiappe, a paleontologist at the Natural History Museum of Los Angeles County who did not participate in the dig.
Scientists said the fossils -- discovered in the Chinese province of Liaoning, northeast of Beijing, at a site that has yielded several important specimens in recent years -- revived a debate between two theories of how dinosaurs might have evolved into birds.
One theory holds that some of these apparent bird ancestors learned to flap their wings to power flight while they were gliding from tree to tree. The other theory suggests they learned to fly by increasing their running speed with their wings and taking off from the ground.
The latest find tends to support the gliding-in-trees theory.
Details of the fossils appear in today's issue of the journal Nature.
Paleontologist Xing Xu of the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences described six fossils with leg feathers arranged in a pattern similar to wing feathers in modern birds.
The feathered legs amount to rear wings, Xu said. He speculated they could have represented an intermediate stage of development before the emergence of true flight powered by flapping the wings. Or, the feathered legs could have been an evolutionary dead end, other researchers said.
Scientists believe Microraptor gui probably did not fly by flapping its wings, because of the way the rear legs are set in the hip sockets and because the rear legs probably would have encountered turbulence from flapping front wings. That suggests instead that both sets of wings were used just for gliding, Chiappe said.