by R. Monastersky
In the academic cockfight over bird origins, dinosaur researchers have discovered something to crow about. Two species of feathered dinosaurs have turned up in China, clinching the argument that birds arose from meat-eating dinosaurs, reports an international team of paleontologists this week.
"This is the most important dinosaur discovery of this century," says one of the researchers, Philip J. Currie of the Royal Tyrrell Museum of Paleontology in Drumheller, Alberta. "The credibility of the dinosaur-to-birds theory has just taken a gigantic leap ahead with these specimens."
Since the 1860s, scientists have been debating whether dinosaurs sired birds. In recent years, numerous finds have supported the hypothesis that birds descended from two-legged, running dinosaurs called theropods (SN: 8/23/97, p. 120). Dramatic evidence emerged in 1996 with the discovery of a Chinese theropod, Sinosauropteryx, that bore a coat of downy fibers, perhaps the evolutionary forerunners of true feathers.
A few researchers, however, have pecked at the theory, arguing instead that birds evolved from four-legged arboreal reptiles. They regard any similarity between birds and dinosaurs as an example of convergent evolution, by which two independent groups grow to look alike. These critics maintain that Sinosauropteryxs fibers were not down but actually a reptilian frill.
The plumage on the new Chinese dinosaurs brushes away such arguments because it is identical to bird feathers, says Currie. The structures have a central shaft with parallel barbs on either side, report Ji Qiang and Ji Shu-An of the National Geological Museum in Beijing, Currie, and Mark A. Norell of the American Museum of Natural History in New York at a press conference on June 23 at the National Geographic Society in Washington, D.C., and in the June 25 Nature.
The two new Chinese dinosaursbetween 145 million and 125 million years oldcome from the same fossil treasure trove in Liaoning province that yielded Sinosauropteryx. One of the feathered dinosaurs is named Protarchaeopteryx robusta because it had a more primitive anatomy than the oldest known bird, the 150-million-year-old Archaeopteryx. Two other specimens belong to a new species, Caudipteryx zoui, which is the closest known relative of birds.
The fossils are considered theropod dinosaurs rather than true birds because they lack a number of features seen in Archaeopteryx and more advanced birds, says Norell. He and his colleagues doubt that the creatures could fly because they had relatively short forelimbs, short feathers, and a body twice the size of Archaeopteryx. Whats more, their feathers had a symmetrical shape like that seen in flightless birds today.
Critics of the bird-dinosaur theory remain unflappable in the face of the new evidence. Ornithologist Alan Feduccia of the University of North Carolina at Chapel Hill surmises that the new finds are actually ancient birds that lost the power of flight and came to resemble theropods superficially. "The fact that they had elongate feathers indicates that they came from a flighted ancestor," he says.
Such arguments dont fly with most paleontologists, however. "These are animals that seem to be, by all appearances, fairly conventional dinosaurs. They are not flightless birds," says Lawrence M. Witmer of Ohio University in Athens.
If feathers appeared first on ground-dwelling dinosaurs, then they must have originally served some purpose unrelated to flight. Some scientists speculate that down, like the Sinosauropteryx structures, evolved first and insulated the bodies of small theropods. Large plumes later may have served as a display for attracting mates.
From Science News, Vol. 153, No. 26, June 27, 1998, p. 404.
Copyright Ó 1998 by Science Service.
Qiang, J., P.J. Currie, M.A. Norell, and J. Shu-An. 1998. Two feathered dinosaurs from northeastern China. Nature 393(June 25):753.
Monastersky, R. 1998. Feathered dinosaur makes debut. Science News 153(Feb. 7):95.
______. 1997. Biologists peck at bird-dinosaur link. Science News 152(Nov. 15):310.
______. 1997. A fowl fight. Science News 152(Aug. 23):120.
Philip J. Currie
Royal Tyrrell Museum of Palaeontology
Drumheller, Alberta T0J 0Y0
University of North Carolina
Department of Biology
Campus Box 3280
Chapel Hill, NC 27599-3280
Lawrence M. Witmer
College of Osteopathic Medicine
Department of Biological Sciences
Athens, OH 45701
copyright 1998 ScienceService