[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
RE: Combined answer Archaeopteryx running...
Jim Cunningham wrote:
> > The long fingers of pterosaurs supported the wing.
> Only the 4th finger. The other three supported the wing when the wing
> was on the ground.
I'll try and clarify what I meant. True, the 4th finger of pterosaurs
supports the distal portion of the wing, leaving the other digits (I-III)
free. Birds adopted an entirely different strategy to pterosaurs, which
make them a poor comparison in terms of the function of the manus. Instead
of a skin membrane strung between the forelimb skeleton and the torso (?and
hindlimbs), they had feathers attached solely to the forelimb skeleton. The
second finger became involved in supporting the distal wing, through the
attachment of the primaries, and the first digit became the alula.
(I don't mean to imply that this all new to you, Jim; I'd bet dollars to
donuts you know more - far, far more - about pterosaur vs bird wings than I
do. I'm just trying to point out that we can track the transformation from
grasping forelimb to wing in theropods, whereas the fossil record has yet to
yield the "proto-wing" stages of the Pterosauria [or their as-yet-unknown or
-unrecognized ancestors]. Therefore, we don't know at what stage the 4th
digit was accorded a central role in supporting the pterosaur wing. On the
other hand [so to speak], we can be pretty sure that for birds, the manus'
involvement in aerial locomotion came *before* the advent of powered flight.
There's a little more on this below...)
> > Did the immediate ancestors of the Pterosauria retain a prehensile
> >manus, or was it absorbed into the flight surface from the get-go?
>It was never absorbed into the flight surface.
The 4th manual digit was integrated into the pterosaur flight surface. It's
indispensable in this respect. My comment was that we don't know if the
flight surface of "proto-pterosaurs" was supported by the hand (the 4th
digit, in this case), or whether the wing surface it was extended distally
at a later stage. We do know which is true for birds (the former). As I'm
sure you know, modern mammalian gliders show different morphologies in this
respect - in some gliders the hand contributes to support of the patagium
(e.g. "mitten gliders"), in others the hand is free of patagial attachment.
> > I DO believe Archie's anatomy was conservative - at least
> > osteologically. Again, I think Ostrom is spot-on. Stripped of its
> > feathers, one would be hard put recognizing _Archaeopteryx_ as a
> > flighted bird.
>And that is exactly why I think archie is not conservative.
Maybe I need more coffe, but I don't know what you mean by this paradoxical
Tracy Ford wrote:
> >Then why did pterosaurs retain the manus all the way to the K/T?<<
> Not all of them did. According to Benett's SVP talk in Mexico City,
> Nyctosaurs (with that weird crest) lacks a manus, and he was referring
> to all Nyctosaurus.
Very interesting - I didn't know this.
And thanks for the D'oh! D'oh! remark - it certainly cheered *me* up! :-)
Timothy J. Williams
Iowa State University
Ames IA 50014
Phone: 515 294 9233
Fax: 515 294 3163