CORVALLIS, Ore. - Scientists today announced the discovery of the oldest animal ever known to have feathers, which may have been the ancestor of birds but clearly was not a dinosaur - a discovery that calls into serious question many theories about an evolutionary link between dinosaurs and birds.
Paleontologists at Oregon State University say the animal, Longisquama insignis, was a small reptile with feathers. It glided among trees in central Asia 220 million years ago, around the time of the earliest dinosaurs and 75 million years before the first bird.
This discovery, to be outlined Friday in the journal Science, may answer some major questions about the earliest development of birds, compel changes in widely accepted theories of evolution and ruffle some feathers in museum exhibits around the world.
"These are some amazing fossils, and at the very least they prove that feathers did not evolve in dinosaurs," said John Ruben, an OSU professor of zoology. "The supposed link between dinosaurs and birds is pretty entrenched in paleontology, but it's not as solid as the public has been led to believe."
While the fossil evidence examined in this study does not conclusively prove that this animal was indeed the ancestor of flying birds, Ruben said, it's clearly consistent with that possibility.
"We can identify certain structures in these fossils that you only find in feathers and just don't see anywhere else," said Terry Jones, also an OSU paleontologist and co-author on the study. "So we're quite sure we're looking at the earliest feather. But beyond that, this animal looks like an ancestral bird even if you ignore the feathers. The teeth, pectoral structure, neck, and skull are just like those of birds."
Scientists from the University of Kansas, Russian Academy of Sciences, University of North Carolina at Chapel Hill, City University of New York, College of Charleston and Sonoma State University also contributed to this study.
The fossils themselves, Ruben said, were found in Kyrgyzstan in 1969 and had actually been laying in a drawer in Moscow for decades, initially identified as an animal with scales, not feathers. They chanced across them at a touring exhibit of Russian fossils last year.
"I had been asked to give a talk on dinosaur biology in a Kansas City shopping mall where this exhibit was," Ruben said. "Terry Jones and I took one look at these fossils and we realized immediately this was a very old animal with feathers. We stayed up all night in a vacant store in the mall to study it."
About another year of research in collaboration with some of the world's leading experts convinced the scientists they were looking at the oldest fossils ever found that showed an animal with feathers. A key, they say, is fossil evidence of a unique "sheath" that's essential to the growth of feathers, which is later shed.
Longisquama was a small, lizard-sized glider. It had four legs and feathers on its body that would have been adequate for gliding but lacked the musculature for flying, Ruben said.
The oldest animal prior to this that everyone agrees was a feathered bird is called Archaeopteryx, which first appears in the fossil record about 75 million years after Longisquama. It has been a huge mystery where the feathers of Archaeopteryx evolved from, and many experts had theorized they were linked to dinosaurs.
"A point that too many people always ignored, however, is that the most birdlike of the dinosaurs, such as Bambiraptor and Velociraptor, lived 70 million years after the earliest bird, Archaeopteryx," Ruben said. "So you have birds flying before the evolution of the first birdlike dinosaurs. We now question very strongly whether there were any feathered dinosaurs at all. What have been called feathered dinosaurs were probably flightless birds."
On the other hand, Ruben said, Longisquama would have lived in the right time, and had the right physical structure, to have been the distant evolutionary ancestor of birds.
"Feathers are a very complicated structure," Ruben said. "The odds of them evolving first in Longisquama and then separately at some later point in dinosaurs or any other group of animals would have been astronomically small.
"However, given the feathers on Longisquama and about 75 million more years, it would be a fairly easy developmental step for the feathers to grow at a different location, such as the forearms," he said. "In an evolutionary sense, it's not very far from this animal to a bird with flight."