NEW YORK (AP) -- Scientists say dinosaur fossils discovered in China with feather-like features suggest the creature was warm-blooded -- a theory that could heighten the debate over the fundamental nature of dinosaurs.
Researchers have long argued whether dinosaurs were warm- or cold-blooded. The new study also touches on the debate over why feathers arose.
The Chinese fossil discovery made headlines last year because it appeared to show the creature had primitive feathers. Some scientists said it confirmed the widely accepted notion that birds evolved from dinosaurs.
Others objected, saying it's not clear whether the fossils really show anything related to feathers. The debate continues.
In Thursday's issue of the journal Nature, Chinese researchers described two specimens of Sinosauropteryx prima, both discovered by farmers northeast of Beijing.
The dinosaur was basically the size of a turkey with a long, lizard-like tail. One specimen measures about 2 feet long from the snout to the tip of the tail, and the other is somewhat bigger. The dinosaur walked on its hind legs and had short, stout forelimbs.
Scientists are debating how old the fossils are, with estimates ranging from around 120 million years to about 140 million or older.
The specimens are squished, fossilized remains pressed into slabs of rock, showing the dinosaur in profile. The feather-like features appear along the neck, back and tail.
Scientists have two main theories about why feathers first evolved -- flight and insulation. The feather-like features on the Chinese dinosaur give no sign of being useful for flying, the Chinese scientists said.
Instead, their presence may mean that Sinosauropteryx was warm-blooded and used the feather-like features to retain heat, the scientists said. If the dinosaur were cold-blooded instead, the feathery features would have prevented it from warming up by basking in the sunshine, the researchers said.
Scientists have long debated whether dinosaurs were warm-blooded, cold-blooded or something in between. The Chinese fossils may prove important in sorting that out, said dinosaur specialist David Weishampel of the Johns Hopkins University.
Luis Chiappe, who studies the evolution of birds at the American Museum of Natural History, said he thinks theropod dinosaurs and early birds were in an intermediate category between warm-blooded and cold-blooded.
He also said "it's a tough call" to decide whether the Chinese dinosaur shows anything related to feathers. If any chemical traces of the original material remain, analysis might show whether they contain a protein specific to feathers, he said.
For now, he said, "In the deep of my heart I believe they are precursors of feathers."