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>Most gliders, of course, never evolve powered flight. They evolve other
>specializations toward becoming better gliders, either because their
>particular gliding adaptations prohibit (or at least render extremely
>unlikely) the evolution of flight (e.g., flattened ribcages) or simply
>because the requisite adaptations simply did not appear in their lineages.

Precisely my point - the evolution of gliding is not simply a way-station on
the road to powered flight, and may in fact have nothing to do with it.

>A long tail will help to keep a gliding animal aloft while its forelimbs
>undergo the required incremental changes from unpowered-gliding organs
>through powered-flight organs. The earliest pterosaurs and birds all had long
>tails and rear flight surfaces (the earliest bats are unknown, but I bet they
>had long tails, too), and these were discarded through evolution (too much
>drag) once powered flight was achieved.

However, this is only true to a limited degree for specialized gliders - of
course the "flying" frogs are tailless, and the only glider I can think of
with a long free tail that appears modified for gliding is the tiny
feathertail glider of Australia.  I am not aware (though I could be wrong)
that the tails of flying squirrels, say, have any role in gliding.  Of
course the most accomplished glider, the colugo, has the tail enclsed in the
gliding membrane.

I wonder if the advantage of a long tail might have more to do with steering
(thus possibly supporting my armchair guess that flight may have evolved
first for increased maneuverability in close quarters rather than for
long-distance travel).
Ronald I. Orenstein                           Phone: (905) 820-7886 (home)
International Wildlife Coalition              Fax/Modem: (905) 569-0116 (home)
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