JONES, T.D.*; RUBEN, J.A.: Feather origins and the myth of “feathered dinosaurs”

The origin of feathers has been linked to flight and/or insulation. Recent discoveries of dinosaurs with feathers or presumed feather precursors have been used to substantiate the latter hypothesis. However, analyses of the nasal passages and associated sinuses demonstrates that dinosaurs and early birds, including Archaeopteryx, were likely to have been ectothermic and, therefore, would have no need for insulation. Additionally, the presence of feathers in Longisquama, a Triassic gliding archosaur, suggests that feathers did not originate among the Dinosauria and were associated with origins of flight. Moreover, cursorial bird-like running style of the only unambiguously feathered taxon (Caudipteryx), suggests that it may have been a secondarily flightless bird. Based on these data, we conclude that feathers preceded dinosaurs, that they were originally associated with flight, and took on an insulatory role in conjunction with the origins of endothermy in birds.