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Dinosaur find raises debate on feather evolution
2009-03-18
NEW YORK - A small dinosaur that once roamed northeastern China was covered with a stiff, hairlike fuzz, a discovery that suggests feathers began to evolve much earlier than many researchers believe -- maybe even in the earliest dinosaurs. Scientists had previously identified feathers and so-called "dinofuzz" in theropods, two-legged meat-eaters that are widely considered the ancestors of birds. But the Chinese creature is only distantly related to theropods, and the hollow filaments of its fuzz may be primitive feathers, say the scientists who report the find in Thursday's issue of the journal Nature. Dinosaurs split into two branches early on, more than 235 million years ago. Theropods belong to one branch, and the Chinese creature is a primitive member of the other branch. Maybe both branches inherited primitive feathers from common ancestors before or at the split -- in other words, the first dinosaurs, the researchers suggest. Some other experts said they're not ready to buy that argument. No fossils from the first dinosaurs are known, while the fossil record for feathers goes back about 150 million years. The dinosaur find is reported by scientists at the Chinese Academy of Sciences and the Chinese Academy of Geological Sciences, both in Beijing, and elsewhere. The creature lived sometime between 144 million and 99 million years ago. It walked on two legs and had a long tail. The discovered specimen -- apparently not an adult -- measured only about 28 inches long overall. It's not clear what the creature ate with its fang-like teeth. The study authors named the creature Tianyulong confuciusi. The name comes from the Shandong Tianyu Museum of Nature in Shangdong Province, which houses the specimen, and the philosopher Confucius. Tianyulong's remains, laid out on the surface of a stone slab, show three patches of hair-like fuzz. The filaments were generally about 1.5 inches long, but those on the tail were a bit more than 2 inches long. While the study authors argue that primitive feathers may have been found in the earliest dinosaurs, they suggest that some later species lost them during evolution. In a Nature commentary, Lawrence Witmer of the Ohio University College of Osteopathic Medicine said it's not yet certain whether Tianyulong's filaments are part of the evolution of feathers. "Perhaps the only clear conclusion that can be drawn ... is that little Tianyulong has made an already confusing picture of feather origins even fuzzier," Witmer wrote. Mark Norell, a prominent dinosaur researcher at the American Museum of Natural History in New York, said he'd already believed that the first dinosaurs had primitive feathers. He believes most dinosaurs had something related to feathers, but that lack of preservation has hidden that in the fossil record. But Luis Chiappe, director of the Dinosaur Institute at the Natural History Museum of Los Angeles County, who has written about the origin of feathers, said he doubts that feathers evolved outside of theropods and birds. Interpreting Tianyulon's filaments as early feathers is questionable because of their appearance, he said. Moreover, Chiappe said, given the apparent lack of feathers in many dinosaur species, "I don't see any reason why you're going to conclude that feathers must have originated before the origin of dinosaurs or (at) about the same time." ___ On the Net: Nature: http://www.nature.com/nature
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