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Re: thoughts on Pterasaur feet

Adam Yates wrote:
> It struck me that if what you say about
> the long toe of the pterosaur foot is true then it could be an example of
> the same phenomenon. However the fact that the elongated toe is the fifth
> digit of the foot while the elongated finger is the fourth digit of the
> hand, so they are not "homologous" in the sense that I am using the word.
> Unless of course our interpretation of the pterosaur manus is incorrect
> and the wing finger is not the fourth....

I may still be missing something here.  The foot of a pterasaur has 5
toes, even in the later pteradactlids.  The wing has only 4 fingers; the
three hand-claws, and the wing-finger -in all forms.  Why do we think
the wing finger is the 4th digit, and not, say, a fusing of the 4th and
5th?  What do most paleontologists think happened to the 5th wing
digit?  When would it have been lost, if that's what happened to it? 
Wellnhofer thinks it simply regressed, but he doesn't indicate why he
thinks so.  I know several bats that have the leading digit of the wing
(2) -not the thumb-and the next digit (3) almost overlapping and having
minimal tissue between them (I don't beleive these digits can be
separated by the animal either), and in some cases, (2) is reduced to a
few floating bones on the leading wing edge-which if it's similar here,
could mean either 4 or 5 on a pterasaur could be regressed this way.

           Betty Cunningham  
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