Image: MICK ELLISON, American Museum of Natural History
An exquisitely complete feathered dinosaur has emerged from the famed fossil beds of northeastern China's Liaoning Province. The new discovery, announced today in the journal Nature, gives further weight to the argument that birds evolved from dinosaurs and provides the strongest evidence yet that feathers pre-date the origin of flight.
Earlier finds from Liaoning had hinted at the presence of featherlike structures on several dinosaur specimens, but critics charged that the structures were instead fibers of the protein collagen or that the fossils represented not dinosaurs but flightless birds. Opponents of the bird-dinosaur connection also noted that no feathers were known from dromeosaurs¿a group of small- to medium-size theropod dinosaurs that exhibit numerous traits in common with birds and are therefore widely held to be their closest relatives.
The new fossil, however, appears to answer both of those arguments. Paleontologist Mark Norell of the American Museum of Natural History in New York City and his colleagues report that the 130-million-year-old specimen represents a dromeosaur covered with filamentous structures that exhibit a branching pattern unique to feathers.
The presence of featherlike structures on such a creature indicates that feathers must have evolved for some purpose other than flight¿perhaps to help the animal keep warm. Indeed, for modern birds, which are warm-blooded, feathers provide critical insulation. Thus, Norell says, non-avian dinosaurs may have developed primitive feathers as they developed warm-bloodedness.