Re: pteros have lift-off

[Augusto Haro <augustoharo@gmail.com>]

Tim Williams wrote:
>
> But Augusto, we know from trackways that pterosaurs used quadrupedal 
> terrestrial locomotion. The question is: did pterosaurs acquire this gait 
> *before* the advent of aerial locomotion, or only after they became fliers?

He, he, great and devastating point in favor of pterosaur
quadrupedalism; then parsimony have nothing to do in that respect. But
I think that, if we were dubious about that pterosaurs were or not
quadrupedal, then parsimony would lean towards the bipedal hypothesis.
Now, as quadrupedalism in pterosaurs is a stated fact, then yes, we
cannot say the state at the most basal node of Ornithodira is
bipedalism, and it is equally parsimonious to admit Ornithodira became
bipedal and later Pterosauria reverted, than to admit that
Dinosauriformes and Scleromochlus independently acquired bipedalism
from a quadruped ancestor. Thus, it is equally parsimonious to admit
pterosaurs derive from quadrupedal or bipedal ancestors, or that they
were biped or quadruped when flight begun.