"Feathered" Dinosaur Was Bald, Not Bird Ancestor, Controversial Study Says
for National Geographic News
|June 1, 2007|
A shadow of doubt has been thrown over the widely held theory that dinosaurs had feathers and that they gave rise to modern birds.
In a new study, researchers examined the fossil of a 140-million-year-old turkey-size dinosaur called Sinosauropteryx.
Other experts had previously concluded that distinctive patterns found on the skin of a Sinosauropteryx fossil were remnants of downy protofeathers, making the species the most primitive feathered dinosaur.
But the new team says that their analysis shows that the creature was actually bald.
The patterns are the remains of "structural fibers, probably collagen—the most abundant fiber in vertebrates—of the skin and the dorsal frill," said lead study author Theagarten Lingham-Soliar of the University of KwaZulu-Natal in South Africa.
The findings were published last week in the journal Proceedings of the Royal Society B.
Lingham-Soliar and colleagues' results support the arguments of a small but highly vocal group of scientists who say there's no evidence of dinosaurs ever having feathers.
"The existence of protofeathers in these dinosaurs was considered critical evidence that birds were derived from dinosaurs," said study co-author Alan Feduccia, a bird evolution expert at the University of North Carolina at Chapel Hill.
"What we have shown is that there's absolutely no evidence whatsoever that protofeathers existed in dinosaurs, period."
But the majority of scientists in the field are unconvinced.
"These people have been flogging the same horse for a long time," said Kevin Padian, curator of the University of California Museum of Paleontology.
"It is appalling that Proceedings B chose to publish this nonsense."
Making the Case
Sinosauropteryx, which means "Chinese lizard-wing," lived in China during the early Cretaceous period, about 144 to 127 million years ago.
The animal was about three feet (a meter) long, with most of its length coming from its extremely long tail.
The discovery of protofeathers was based on a specimen found in 1996 in Liaoning Province in northeastern China (photos: China's fossil marvels).
Mark Norell, the paleontology chair at the American Museum of Natural History in New York, has co-authored several papers describing evidence of feathers in other dinosaur fossils.
(Read "New Dinosaur Discovered: T. Rex Cousin Had Feathers" [October 6, 2004].)
Norell, who is also a National Geographic Society Committee for Research and Exploration grantee, said that such finds have firmly established the link between dinosaurs and birds.
(National Geographic News is part of the National Geographic Society.)
"There's a preponderance of evidence supporting the idea that birds are nested within theropod dinosaurs," he said.
Therapods—a diverse group of carnivorous dinosaurs that includes Tyrannosaurus rex—share a number of physical characteristics with modern birds.
Current theory says that over time theropods developed plant-eating habits, grew feathers to keep warm, and took to the trees for safety.
But skeptics of this theory argue that birds evolved earlier from a common ancestor with dinosaurs, and that dinos never had feathers.
For the new study, researchers looked at a recently discovered Sinosauropteryx specimen also found in Liaoning.
"The peripheral dorsal structures are the remains of fiber reinforcement of the frill" that extended from the head to the tip of the tail of the dinosaur, said lead author Lingham-Soliar.
"Their regular nature and straightness defies the notion of them being soft pliable structures [like feathers] but rather high-tensile fibers such as collagen."
The fibers show a striking similarity to the collagen found on the skin of sharks and reptiles today, the authors say.
And without protofeathers in Sinosauropteryx, the authors argue, the theory that feathers first evolved in dinosaurs—not for flight but for insulation—falls flat.
David Unwin, a vertebrate paleontologist at the University of Leicester in England, considers himself neutral on the issue.
He said that scientists need to better understand how soft tissues in well-preserved dinosaurs are actually fossilized.
(Read "Dinosaur Soft Tissue Sequenced; Similar to Chicken Proteins" [April 12, 2007].)
But the new study falls short because it relies only on microscopic analysis, with no additional CAT scans or chemical tests, he said.
"They merely looked at the tissues and said, Oh, they're straight and well organized it must be collagen," Unwin said.
In some cases, he said, the fibers do look like collagen.
"But what they didn't draw attention to is that there are other tissues in there that don't look like collagen and might be protofeathers."
And what about the many other dinosaurs that appear to have been feathered?
Feduccia, the study co-author, says these creatures are actually descendants of birds that lost their ability to fly.
"When they become flightless, they superficially resemble small dinosaurs," he said.
Storrs Olson, the curator of birds at the Smithsonian Institution's National Museum of Natural History, has been a vocal critic of the theory that modern birds evolved from dinosaurs.
"The whole notion of feathered dinosaurs is a myth that has been created by ideologues bent on perpetuating the birds-are-dinosaurs theory in the face of all contrary evidence," he said.
National Geographic magazine and other media have heavily publicized stories about feathered dinosaurs. But contrarian views struggle to get heard, Feduccia said.
"One of the primary arguments used to deflect our view is that we are a fringe group," he said. "But if science operates by a majority view, we're in serious trouble.
"We are dealing here basically with a faith-based science where the contrarian view is silenced to a large extent by the popular press," he added.
The University of Leicester's Unwin said that science benefits from opposing views, "because it keeps the people who are arguing for a dinosaur origin for birds on their toes."
But, "to be brutally honest, the contrarian views on this issue haven't been particularly strong," he said. "I don't know if they have really helped shape our ideas about the origin of birds in any serious way.
"One way the [latest] paper may be significant, though, is that it suggests that the story of the origin of feathers may not be quite as simple as we would like to have it."
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