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Re: Feduccia (was: polarity of bipedality in dinosaurs)



At 16:11 24/09/96 -0500, Norm King wrote:

>Of course, pterosaus have very short trunks, and the hind legs are not 
>substantially involved in flight. Is there some other model for the 
>ancestor of a pterosaur than a gliding quadruped?  If gliding quadruped 
>is the model for pterosaurs, then could that not also be a model for 
>birds?
>
>*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
>Norman R. King

I take your point, but I note that it is unclear just how much the hind limb
was involved, and furthermore we ar no further ahead at finding a gliding
precursor for pterosaurs (or bats, for that matter) than for birds, so zero
plus zero still equals zero.  I admit I have a greater willingness to
believe in gliding proto-bats or pterosaurs because the wing is a stretched
membrane - quite unlike the condition in birds.  Mind you, I think that is
the point of Feduccia's Saki example, as the gliding surface is hair
extending from the forearm.

My alternate for birds was the idea of an arboreal animal (probably at least
a functinal biped, but that is not an essential part of the idea) developing
structures to assist, not in getting from tree to tree, but in fluttering or
leaping upward within a tree (to reach, say, insects on leaves or branch
tips).  Otherwise, why develop a flapping mechanism?  As we know,
non-flapping gliders can travel very long distances (over 100 feet for the
colugo and some large Asian flying squirrels), and as gliding is so low-cost
energetically there may be little pressure to add a flapping component
(unless the forests thin out to a very great degree).  However, gliding will
be of no help whatever to a predator trying to get at prey that may be at
much closer range but just out of reach ABOVE it, whereas flapping could
make all the difference in the world.
--
Ronald I. Orenstein                           Phone: (905) 820-7886 (home)
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