Re: NO SECONDARILY FLIGHTLESS THEROPODS

[Dinogeorge <Dinogeorge@aol.com>]

In a message dated 98-04-04 03:15:00 EST, m_troutman@hotmail.com writes:

<< However, as compelling and intriguing as these hypothesis are, they do 
 not fully appreciate the fundamental bauplan that flightless birds have.  >>

You are talking about how birds of a >modern< aspect might evolve into
flightless forms. This is not particularly relevant to how birds of a >very
primitive< aspect--having elongate tails, hind limbs powered by extensive
caudal musculature, and grasping forelimbs doing double duty as not
particularly efficient wings--might have evolved into flightless forms. The
fundamental bauplan of an avialan bird is quite different from the fundamental
bauplan of an early dino-bird, and one may reasonably expect that
flightlessness would evolve through a different mechanism in birds of a modern
aspect from that in dino-birds. The only thing that remains relevant is that
flightlessness among birds of any kind occurs much more frequently than the
opposite.

<<The only "flightless" birds that do not show paedomorphic features are 
the penguins and auks. But, since these birds are essentially still 
"fliers" ( have anyone ever seen a penguin " fly " through water? ) 
there should be no reason why all of the typical flightless bird 
characteristics ever evolved. These birds will be excluded from this and 
when I say flightless birds I mean the typical flightless birds.>>

Here you are excluding from the discussion an example of the evolution of
flightlessness that evidently does not conform to your idea that
flightlessness appears through paedomorphosis--indeed, an example that
contradicts your thesis that avian flightlessness evolves exclusively through
paedomorphosis. Obviously, penguins don't fly; they have evolved from
previously flying forms into forms that swim through water. Likewise,
theropods didn't fly; they evolved from previously flying forms into forms
that walked, ran, and hunted on the ground.

What you are saying is, all birds that have become flightless through
paedomorphosis have become flightless through paedomorphosis.