Phylogenetic context for the origin of feathers

A number Of hypotheses have been suggested for the origin of birds and feat hers, Although distributions of functional complexes have frequently been u sed to test phylogenetic hypotheses, analysis of the origin of feathers rem ains hampered by the incomplete fossil record of these unmineralized struct ures. It is also complicated by approaches that confuse the origins of bird s, feathers, and flight without first demonstrating that these relate to th e same historical event. Functional speculation regarding the origin of fea thers usually focuses on three possible alternatives: (1) flight; (2) therm al insulation; or (3) display. Recent fossil finds of Late Cretaceous feath ered dinosaurs in China have demonstrated that feathers appear to have orig inated in taxa that retained a significant number of primitive nonavian fea tures. Current evidence strongly suggests that birds are theropod dinosaurs , and that the most primitive known feathers are found on nonflying animals . This further suggests that feathers did not evolve as flight structures. Thermoregulatory, display, and biomechanical support functions remain possi ble explanations for the origin of feathers, As the earliest function of fe athers was probably not for aerial locomotion, it may be speculated that th e transitional animals represented by the Chinese fossils possessed skin wi th the tensile properties of reptiles and combined it with the apomorphic c haracteristics of feathers.