The discovery of a new feathered dinosaur in China bolsters the idea that feathers first evolved for insulation, according to a team of Chinese and American scientists.

The new fossil, discovered in 130 million year old Early Cretaceous fossil beds in China's Liaoning Province, is only the latest in a rapidly growing list of Chinese feathered dinosaurs. However, the new specimen is important because it is the first to show feathers covering the entire animal.

"This is the specimen we've been waiting for," said Ji Qiang, a co-author of the Nature paper in which the specimen was discussed.

Although it has been known for over five years that dinosaurs possessed primitive feathers, there has been a debate as to why they evolved. This new specimen shows that dinosaurs may have evolved feathers for insulation before they were used for flight, an idea that many scientists have hypothesized but have been unable to prove.

"There's strong evidence that these body coverings were originally insulation for warm-blooded dinosaurs and were only later co-opted for flight,'' said Mark Norell, a paleontologist at the American Museum of Natural History in New York and co-author of the Nature paper.

Measuring about a half-meter in length, this new dinosaur has been assigned to the dromaeosaurid family. It is anatomically similar to Velociraptor and Microraptor, and is considered a smoking gun for paleontologists who support the belief that birds evolved from dinosaurs. Despite its importance, the discovery has not yet been named. Some scientists believe that it is a juvenile of the genus Sinornithosaurus, while others argue that it is a new genus and species.

The feathers that covered the body of this animal varied. Downy fibers covered its head and tail, while tufts of integument that resemble primitive feathers sprouted from other parts of the body. Branched structures, similar to modern feathers, grew on the backs of the animal's arms. These more advanced feathers are rarely seen in dinosaurs. University of Maryland paleontologist Thomas Holtz is intrigued by these structures.

"The patterns suggest that structures such as barbs seen in modern feathers were organizing the feather fibers into adjacent rows of parallel lines. The fossil makes it increasingly plausible that theropods - including Tyrannosaurus rex - were fluffy and not scaly, at least in their adolescence…sort of fuzzy killing machines," Holtz said.

In addition to strengthening the notion that feathers evolved for insulation, this new species gives more evidence to the hypothesis that some dinosaurs may have been warm blooded.

"Modern birds are warm-blooded and their feathers play an integral role in keeping them warm, so a reasonable idea is that non-avian dinosaurs developed primitive feathers at the same time that they developed warm-bloodedness," said Norell. "It's conceivable that smaller dinosaurs like this one and even the young of larger species like Tyrannosaurus rex may have needed feather-like body coverings to maintain their body temperature."

Several scientists, including Norell and University of Kansas ornithologist Richard Prum, believe that this new species is a smoking gun in the dinosaur-bird debate.

"It is now impossible for any credible person to claim that birds are not theropod dinosaurs,'' Prum said.

Despite Prum's words, a small group of scientists still denies that birds evolved from dinosaurs, and says that this new species does nothing to discredit their belief.

"To me it's the best specimen yet showing that these structures are not feathers," said Storrs Olson, curator of birds at the National Museum of Natural History at the Smithsonian Institution and a major opponent of the dinosaur-bird evolution theory. "There's nothing there that has a structure like a feather."

Olson added that the feather-like covering on the new specimen may be many things, including impressions of decaying skin or mineral crystals.

Prum does not support Olson's viewpoint, though.

"It's the final straw. We've all lived long enough for the dino-deniers to have to face the evidence. This comes as close to proof as we find in science," he said.

The paper on this new specimen was published in the April 25th issue of Nature, and the fossil will be on display at the American Museum of Natural History into the near future.

© 2000 brusatte@theramp.net