WASHINGTON — Some experts believe unique feathers found on the fossil of a 120 million-year-old bird has called into question the theory that birds evolved from dinosaurs. Other experts disagree.
In a study appearing today in the journal Science, two Chinese researchers report that a fossil called Protopteryx — from a group of flying animals called Enantiornithine — includes feathers that are "different from those of all other known fossil and modern feathers."
Fucheng Zhang and Zhonghe Zhou of the Chinese Academy of Sciences suggest the discovery supports the idea that feathers evolved from scales, like those on reptiles.
Some researchers say that if feathers developed from scales, then the new fossil is proof that birds and dinosaurs evolved independently from a common reptilian ancestor.
Others insist Protopteryx adds nothing to the dino-bird debate.
"There is nothing in the skeleton of this bird that disputes the dinosaur origin of birds," said Thomas R. Holtz Jr., a University of Maryland paleobiologist and specialists on bird evolution. "The fact that this Protopteryx has these weird, flat feathers really doesn't affect that issue."
Yet Alan Feduccia, an evolutionary biologist at the University of North Carolina, said the Chinese study of Protopteryx "is a hot paper . . . that directly contradicts the idea that birds evolved from dinosaurs."
The new fossil was disclosed a day after researchers announced another ancient Chinese bird, called Microraptor zhaoianus, supported the dinosaur origin of birds.
In the Protopteryx study, Zhang and Zhou described the feather and bone structure in a fossil of a starling-sized bird uncovered in northern China, the site of many dinosaur fossil finds.
The Chinese researchers said the feathers have some characteristics of modern feathers, but the structure is more primitive than feathers found on Archaeopteryx, the earliest known bird.
Archaeopteryx appeared about 145 million years ago, while Protopteryx was dated as more recent, about 120 million years ago. Microraptor, about the size of a crow, lived about 125 million years ago.
Some elements of the Protopteryx wing bone and muscle structure match those of modern birds, said Zhang and Zhou, but the wing retains a claw found on some primitive birdlike animals. In modern birds, that claw is replaced by a structure that adds lift to the wing. Nonetheless, Protopteryx is thought to have been a competent flier. Most dinosaur researchers believe birds evolved 150 million to 180 million years ago from a dinosaur group called Theropods. Researchers cite fundamental skeleton similarities to support the theory. The evolution of feathers, however, has been less clear.
Some experts believe feathers evolved specifically to support flight, while others say feathers evolved first to provide warmth or protection from water.
Larry Martin, a University of Kansas paleontologist, said the Chinese researchers' paper "is the strongest evidence yet that bird feathers evolved for flight and that they were derived from scales."
Holtz notes, however, that Protopteryx, with its primitive feathers, lived millions of years after Archaeopteryx, which had feathers almost identical to those of modern birds.
On the Net:
Science journal: www.eurekalert.org
Theropod evolution: www.micro.utexas.edu/courses/mcmurry/spring98/21/justin.html