Re: Pterosaur wing membranes

[Michael Habib <mhabib5@jhmi.edu>]

> If Darren is referring to the photos that I've seen, they were 
> ambiguous at best about an ankle attachment....

One confounding issue that has occurred to myself (and others before 
me) is that there could be membrane attached to the lateral portion of 
the hindlimbs, without that section of patagium actually attaching to 
the forelimb as well.  If the animal folds up enough before burial, the 
difference between the different sections of membrane would be 
difficult to make out in the resulting fossil.

> But, they sure are counterproductive for animals that are making use 
> of dynamic soaring rather than convective soaring.

There is also the possibility that some very early pterosaurs, or even 
immediate pterosaur ancestors, had a broad-wing type patagium that ran 
from forelimb to hindlimb.  The attachment site might have been 
constrained after this, with phylogenetic inertia maintaining the 
hindlimb attachment.  This would lead to the retention of a narrow 
'fillet' (as has already been discussed as a model), when the wing 
chord reduced under selection for dynamic soaring ability.  That is, in 
fact, probably the most likely explanation for a 'fillet' design, 
should it prove accurate.

Cheers,

--Mike Habib