Re: Gliders to Fliers? (Was Re: Ruben Strikes Back)

[Dinogeorge@aol.com]

In a message dated 9/24/99 5:54:03 PM EST, dbensen@gotnet.net writes:

<< There is a very good reason for this, but it is not functional, but 
phylogenic.
 Bats, pterosaurs(we assume), and gliding lizards all evolved from QUADRIPEDAL
 ancestors.  However, the ancestors of birds were most probably BIPEDAL.  For 
a
 quadraped, skin flaps between the legs make sence, they act as a parachute 
(look
 
 at cats), but a bidpedal animal like a small dinosaur would have to rotate 
its
 legs outward at the hip socket (which they couldn't do)  for such a trick to
 work.  It was much easier to evolve controll surfacase on the arms, which 
would
 swimg forward while the animal was jumping anyway, and the tail.  If birds 
had
 evolved from quardribeds, the would look sort of like feathered, beaked bats,
 and woulnd't be nearly as appeling (though I suppose we wouldn't notice). >>

I consider it just as likely that dinobirds were originally quadrupedal 
semi-sprawlers, and that once the forelimbs had become too winglike to be 
used for walking, they would no longer evolve quadrupedal forms. Bipedality 
in theropods would be the >result< of having forelimbs specialized for 
climbing and/or flying, rather than the other way round. Another evolutionary 
"spandrel."