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Re: BADD BCF



In a message dated 95-12-02 16:34:43 EST, Robert.J.Meyerson@uwrf.edu (Rob
Meyerson) writes:

>>The first question I would ask is, does this surface serve as an airfoil in
>>extant birds (it's hard to tell, because it's covered with feathers)? The
>>second question is, do the patagial tensor muscles help draw the wing back
>>during a wingbeat? My guess is that the patagium is one of those features
>>that evolved as an adjunct to gliding or powered flight, because it seems
t=
>oo
>>restrictive for a strictly climbing or grasping forelimb.
>
>Yes to your first question.  As a part of my Ornithology class, I dissected=
> a pigeon.  When you remove the feathers, there is a noticable airfoil
shape=
> to the wing.
>
>No to your second question.  The patagial muscles are a separate entity
from=
> the biceps, which do serve to draw the wing back.
>
>>A most interesting anatomical feature, by the way. I wonder whether
>>dromaeosaurids and other maniraptorans retained one.
>
>Assuming BCF is correct, I would have to say no, since it would probably be=
> incorporated into the biceps.  The patagial muscles force the arm to be=
> held in a perminant V, a major disadvantage for any predator (you would=
> have to explain the loss of the patagium in BCF, by the way).

It would be more difficult to explain its retention in dromaeosaurids, if
this were the case(!). Losing something through vestigialization that
obviously hampers an animal is the usual evolutionary occurrence.

Indeed, BADD theory would have the devil of a time explaining the existence
of a patagial vestige (if one were found) in dromaeosaurids as a "pre-flight"
exaptation. Does the patagium leave any scars or other traces on the wing
bones? If similar scars were found in _Deinonychus_, I would take this as
solid evidence of a volant stage in its evolution.