On the origins of birds: the sequence of character acquisition in the evolution of avian flight

Abstract

Assessment of competing theories for the evolution of avian flight is problematic, and tends to rest too heavily on reconstruction of the mode of life of one or a few specimens representing still fewer species. A more powerful method is to compare the sequence of character acquisition predicted by the various theories with the empirical sequence provided by cladistic phylogeny. Arboreal and cursorial theories incorrectly predict the sequence of character acquisition for several key features of avian evolution. We propose an alternative 'pouncing proavis' model for the evolution of flight. As well as being both biologically and evolutionarily plausible, the pouncing proavis model correctly predicts the evolutionary sequence of all five key features marking the evolution of birds.