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> however, are we to infer that because bats gained the ability to fly through
> gliding from tree to tree, that pterosaurs and birds must have evolved
> through the same mechanism? Does any other paradigm work? Or is there one and
> only one way for a group of animals to develop flight?
Yes, there are apparently other ways, or at least one other way.
But it does not seem to apply to vertebrates.
I am talking about the recent research that strongly suggests an
"aquatic" origin for insect flight. However the dynamics involved
only work for small organisms, and the transitional states rely
on metamorphosis from a pre-adult aquatic form to a non-aquatic
sexual form. Vertebrates, in general, do not show metamorphosis
of this sort (well, living amphibians excepted).
But even in insects an arboreal gliding origin is being seriously
considered. (With the added variation that in this model the basic
wing originated as a thermoregulatory appendage, then switched to
gliding, and finally to flight).
What both insct models have, however, is *experimental* evidence
that the transitional forms could perform the stated function
(heat dissipation or propulsion to shore) *and* that the ability
to perform this function increases right up to the point where
sufficient lift is generated for gliding or flying.
And the aquatic model has the added advantage that two existing
groups of insects *still* live that way.
> And what is the physiological evidence that archaeopteryx was a climber? Is
> it definitive or speculative in nature?
The evidence is mostly in the anatomy of the feet - so far.
When (and if) Dr. Martin's paper on the skeleton is published,
there may be additional evidence. But until then, we have only
his word on what he has found.
Certainly the evidence is, as yet, inconclusive.
The peace of God be with you.