protofeather

Protofeathers were simple, filamentous structures made of keratin that predated true feathers and were likely used for insulation or display rather than flight. Fossil evidence indicates that many dinosaurs, not just birds, possessed these feather-like coverings. These structures evolved before birds and avian flight, suggesting an earlier origin in a common ancestor of pterosaurs, dinosaurs, and birds, possibly around 250 million years ago. Early protofeathers were straight and dense, later evolving into branched and downy forms before developing into the more complex structures seen in modern birds.12345