[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: Cope's Rule in the Pterosauria - Hone & Benton 2007
"Here's a start...
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I have some evidence in hand (as yet unpublished) that the structural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).