I wonder how bats compare as far as these "pre-requisites" are concerned. Anyone here knowledgable on this subject? How do bat lungs compare to bird lungs?
heh, that would be beautiful. unfortunately, i don't know squat about bat. though i am pretty sure they lack the lung function of birds, considering that birds are the ONLY animals that breath this way. other than, apparently, theropod dinosaurs. there's the other reason this argument is totally specious:
theropod skeletons contain, gradually, more and more of specialized fusing and hollowing of bones seen in birds. we know they had air-sacs, like birds. they have the right muscular and skeletal, and probably circulator system. while they're not neccessarily pre-requisites for flight, they do help -- and they apparently help land dwelling theropod dinosaurs, too.