Re: Cope's Rule in the Pterosauria - Hone & Benton 2007

[MICHAEL HABIB <habib@jhmi.edu>]

"Here's a start...

http://dipbsf.uninsubria.it/paleo/bennett.htm";

Thanks to Tim for the URL.  A rather helpful little summary.  The one bit that 
I might question is this:

"The interphalangeal joints of both wings are preserved at about 140º, thus 
flexed much more than is typical of pterosaurs.  As a consequence, the 
wingfinger curved posteriorly and would have produced a wing that had a blunt 
tip and a relatively low aspect ratio. The wing of Jeholopterus clearly has 
four wing phalanges, but the fourth phalanx is very short because of the 
progressive reduction in phalangeal length from proximal to distal. Its wings 
are also preserved with the phalanges strongly flexed as in Anurognathus, such 
that the wings would have a blunt tip and a low aspect ratio: such a wing was 
probably characteristic of anurognathids."

That wing configuration might produce a low aspect ratio wing, but it might 
also have been supporting a backswept high aspect ratio wing.  Either 
configuration is consistent with aerial insectivory, though the specific flight 
dynamics (and prey capture techniques) associated with each will obviously 
differ.  The broad distal wing and low AR would be very similar to the planform 
in vespertilionid bats and some caprimulgiform birds (whip-poor-wills, etc).  
On the other hand, a backswept, narrow wing (with high AR) would be more 
similar to that of swifts, swallows, and some other caprimuligiform birds 
(nighthawks, etc).  There are some impressive wing impressions for 
Anurognathids, of course (especially Jeholopterus).  Interestingly, these do 
not appear to me to be as "clear cut" as one might think.  There are two 
distinct wing shapes that appear to be consistent with the preserved 
impressions: one is a broad wing with a rounded wingtip, and the other is a 
more narrow wing with
 a membrane anterior to the femur helping to form a fowler flap.  The wingtip 
would be more narrow in this case, but likely still somewhat rounded.  Note 
that I say this only based on studying good photographs of the specimens; I 
have not yet looked at the original anurognathid specimens (though plans do to 
so are in the works).

I have some evidence in hand (as yet unpublished) that the structural 
characteristics of the forelimb differ between the two general planform types 
described above.  If confirmed (and it looks good so far), this will provide an 
osteological signal for differentiating wing shape in Anurognathids.  (If my 
abstract is accepted, that data will be presented at SVP).

Cheers,

--Mike H.