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Re: Testing Pterosaurs



> > I can hang my models quadrupedally from the trunks of pine trees
>
>I find this to be an important point.  Like modern flyng squirrels,
>this is likely related to the very origin of pterosaur flight.
>
>swf@elsegundoca.attgis.com             sarima@netcom.com

I have made this point before, but:

I know of no evidence whatever that flying-squirrel-like gliders are stages
in the evolution of powered flight.  There are no such creatures known in
the ancestry of either birds, bats or pterosaurs, and no indication that any
of the various gliding lineages have produced anything more than better
gliders (culminating, I suppose, in the colugo).

Everyone simply assumes that this is the path that was followed.  But it
occurs to me that a highly-adapted glider may be the last creature that
would evolve into a true flyer.  I have watched Draco lizards and Petaurista
flying squirrels in Borneo and can't imagine what they would gain by giving
up the adaptations they already have for a far more energetically-expensive
form of locomotion.

Instead (pure speculation follows) flight may have evolved not in the forest
homes of most gliders but in areas where gliding would be inappropriate
because short-distance tree-to-tree flights might not have been possible (eg
savannas, open country), and some degree of powering may have been required.

An interesting case might be the freshwatere hatchetfishes, which are hardly
elegant gliders like flying fish but actually beat their pectoral fins
rapidly on leaping, in a crude form of powered flight.  The adaptation seems
quite different from that in gliding fishes.
--
Ronald I. Orenstein                           Phone: (905) 820-7886 (home)
International Wildlife Coalition              Fax/Modem: (905) 569-0116 (home)
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