The theory that birds are descended from dinosaurs gained more credence yesterday when paleontologists announced the discovery of fossils of two species with both distinctive feathers and dinosaur features.
The fossils, unearthed in the Liaoning province of China, date back more than 120 million years and conclusively prove the hotly contested theory that dinosaurs are the direct ancestors of birds, said Mr Philip Currie, curator of dinosaurs at the Royal Tyrrell Museum of Palaeontology in Canada.
"Dinosaurs have become almost synonymous with the word controversy in science," Mr Currie told a news conference. "One of the controversies, I think, is finally resolved."
A team of scientists worked to identify the fossils as two separate species and their findings were published in National Geographic magazine and the journal Nature.
Scientists in the dinosaur-bird camp had been looking for a definitive feature such as the feathers to corroborate the relationship between the two, said Mr Ji Qiang, director of the National Geological Museum in Beijing, who worked on the fossils.
It is hard to find the telltale signs that dinosaurs had bird-like traits such as hollow bones and feathers because they are often destroyed in the fossilised record, said National Geographic magazine editor Bill Allen.
"These fossils are things we predicted would be there but seriously in my lifetime I never thought we were going to find them," said Mr Mark Norell, chairman and associate curator in the department of vertebrate paleontology at the American Museum of Natural History in New York, who also worked on the fossils.
The two species, named Caudipteryx zoui (tail feather) and Protoarchaeopteryx robusta, were both fast runners that were probably unable to fly, judging by their short arms and long legs. The feathers may have been for insulation or display, Mr Currie said.
Protoarchaeopteryx was about the size of a modern day turkey, and may have looked like the forebears of Archaeopteryx, the earliest known bird. Most of its body was probably covered with feathers.
Caudipteryx was about three feet tall, the scientists said. It, too, probably had feathers all over its body although the fossils distinctively show feathers only on its tail and hands.
Both animals closely resemble meat-eating dinosaurs called theropods, Mr Currie said.
The fossils show that birds use their dinosaur features for activities that they were never originally intended for, such as flight, said Mr Kevin Padian, curator of the University of California Museum of Paleontology.