Re: bauplan convergence

[Ronald Orenstein <ornstn@home.com>]

At 02:25 AM 17/06/2000 -0700, Scott Hartman wrote:
    This is important, because theropods and Archaeopteryx have deep 
narrow bodies, and long limb elements that keep would keep their center of 
gravity high off their footing, which doesn't help when recovering from a 
boffed jump to the next branch.  I have no problem envisioning theropods 
climbing trees from a functional standpoint (grasping hands, lots of claws 
and what not), but there are simply no theropods (or Archaeopteryx) that 
show scansorial adaptations.  So I doubt scansorial gliding was important 
in the evolution of avian flight.

I quite agree - but this does not mean that flight could not have evolved 
in trees, but without a gliding precursor.  I posted a number of messages 
on this about five years ago, as a matter of fact: my basic point was that 
gliding and powered flight may be quite separate evolutionary strategies, 
with powered flight being more useful for maneuvering within trees by short 
upward leaps (eg to reach a prey item om a leaf or branch tip) without 
having to risk falling out of the tree.  After all, really good gliders can 
cover great distances between trees at low energetic cost, so why fly if 
all you are trying to do is get from one tree to another?
--
Ronald I. Orenstein                           Phone: (905) 820-7886
International Wildlife Coalition              Fax/Modem: (905) 569-0116
1825 Shady Creek Court
Mississauga, Ontario, Canada L5L 3W2          mailto:ornstn@home.com