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At 11:45 06/08/96 -0400, Tim Williams wrote:
>Ronald I. Orenstein says:
>> I still hold to the view that the considerably greater diversity seen in
>> birds than in bats (or pterosaurs) is primarily (though not entirely) due to
>> the fact that birds have decoupled their wing mechanism from the hind limb,
>> allowing a far greater range of adaptations for walking, wading, swimming,
>> climbing etc.
>Not in contradiction to the above statement, but there are those who 
>said that pterosaurs did the same.  Some restorations of certain 
>pterosaurs show their hindlimbs having no part at all in the wing 

I don't think this is exactly the idea.  There is an argument among
pterosaurologists, or whatever they call themselves, as to the extent to
which the hind limb mechanism was involved in supporting the flight
membrane, but I believe there is clear evidence that at least some
pterosaurs possessed a uropatagium stretching between the hind legs, and the
wing certainly needed some kind of posterior attachment to stretch the
membrane so that even if this were only at the hip the hindlimb structure
may have been to some extent determined by the flight mechanism.  You might
want to look at Wellnhofer's "Encyclopedia of Pterosaurs", particularly pp.
146 et seq, for details.  The wing membrane certainly appears to have been
attached to the leg in Pterodactylus at least.

Nonetheless it is certainly true that pterosaurs must have occupied niches
bats have not - there are no bats anywhere near the size of the larger
pterosaurs, for example, and no bat with the dental equipment of a weird
creature like Pterodaustro.  However, bats evolved under such a different
set of circumstances, with major differences in the vegetation and birds
already well-established, that comparing the two in any meaningful way with
respect to their evolution may be a near-impossible task.
Ronald I. Orenstein                           Phone: (905) 820-7886 (home)
International Wildlife Coalition              Fax/Modem: (905) 569-0116 (home)
Home: 1825 Shady Creek Court                  Messages: (416) 368-4661
Mississauga, Ontario, Canada L5L 3W2          Internet: ornstn@inforamp.net
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