Re: pterosaurs in trees...

[Jonathon Woolf <jwoolf@erinet.com>]

Tracy Ford wrote:
> 
> You wrote:
> >
> >This may be true in theory, but *nowhere*, either in the fossil record or in
> >the range of living animals, do we have direct evidence of a gliding animal
> >taking up powered flight.  Even the very earliest examples of pterosaurs,
> >bats, and, I believe, birds were fully powered fliers.  There are gliding
> >marsupials, gliding rodents, gliding primate relatives, gliding frogs,
> >gliding lizards, gliding fish, and even gliding snakes; but none of these
> >groups has made the transition to powered flight.  This suggests to me that
> >gliding and powered flight are two separate and (at least largely)
> >independent adaptations.
> >
> 
> YES!!! Now someone else is on the right track! Like I said before, if
> it was a good enought glider, why would it need to learn to flap?
> 

Perhaps because flapping makes it a better glider?  Most pterosaurs are
thought to have been shore and sea-creatures, analogous in many ways to
seagulls, albatrosses, frigatebirds, and the like.  These birds are
expert gliders, maintaining altitude and airspeed by subtle adjustments
of the wings relative to the airflow, so skillfully that given no more
than a moderate wind of 10-15 knots they can drop ground speed to almost
nil without stalling.  Also, it would seem to me that long-range gliding
actually requires better, more efficient wings than does powered
flapping flight.

If you couple that with another idea I had recently -- that the
mechanics of the wingstroke aren't all that different from the mechanics
of the forelimb swimming stroke used by turtles and penguins -- there
would seem to be some plausible scenarios where a glider/swimmer evolved
the ability to flap as a modification of its swim-stroke, and an
enhancement of its gliding ability.

-- JSW