Tim Williams wrote:
>However, as long as a "ground-up" hypothesis is theoretically *possible*<
Evolution of vertebrate flight from the surface upwards is not theoretical. The example I've used before on this point are the 50 or so extant species of flying fish in the family Exocoetidae. Granted the comparative differences between fish and dinosaurs are many and large, but it is not necessary to qualify as theoretical the fundamental concept that vertebrate flight can originate in animals that can't get up in trees. Whether it did or not in dinosaurs >is< a theoretical discussion, but not the underlying concept.