Dinos with down coats.

Fossils of the earliest known ancestor of Tyrannosaurus rex--those mighty predators among dinosaurs--have been found with clear impressions of downy feathers from head to tail. These "protofeathers" are considered precursors to the feathers found on present-day birds. The paleontologists who unearthed the 130-million-year-old fossils in northeastern China announced in October that their find provides the first direct evidence that tyrannosaurs had protofeathers.

This supports a theory that some dinosaurs evolved a feathery covering to help them keep warm. The early tyrannosaur specie is a five-foot-long dinosaur that has been named Dilong paradoxus. According to Mark A. Norell, a scientist from the American Museum of Natural History in New York, "The discovery of protofeathers in such a primitive tyrannosaur is giving us a much clearer picture than we had even five years ago of how these animals looked and provides even more evidence of the shared evolutionary features between nonavian dinosaurs and living birds." Over the last eight years, paleontologists have excavated dozens of dinosaurs that show traces of the featherlike structures. Such protofeathers may have eventually adapted for flight in the transition of some carnivorous dinosaurs to birds.