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Re: Rhamphorhynchus Perching???



Larry Febo wrote:

<I`m not sure pterosaurs could have perched on a
branch using their feet alone. They didn`t have the
locking tendon mechanism, and no reversed hallux to
aid the grasp. I would think they would have climbed
about in cycad branches with both feet and hands. They
may have been bipedal on the ground,........but, I`ve
never heard Dave Unwin mention this (quite the
opposite in fact!).>

  Ron has described the lack of neccessity for a
"locking" tendon (more of a relative tendon-joint
interaction) that is the hallmark of the Passeres
[passerine birds] and some others; this allows them to
grip in the neutral position, exerting energy to
extend the toe, so that they can sleep perching, which
no other bird can. Dan Bensen had also asked about the
elongated fifth digit. There are a variety of
interpretations of the fifth digit, including as a
"hallucial" [it's the fifth, not first, digit, but the
principle has been the same] digit which would have
grasped. Problems with this, and both Wellnhofer,
Unwin (I think?), and Peters (on his site) have looked
at the question, so I should think that Larry will
have a preety sound interpretation of this, are that
the digit, in some "rhamphorhynchoids," is preserved
with the mesioposterior end of the plagipatagium
[flight membrane] attached to it with a large
extension, resulting in a flight related use for the
toe. *Sordes* and *Rhamphorhynchus* both preserve the
membrane in this position [see Wellnhofer, Sharov].

  This does not mean the toe could not do anything
else when the membrane was relaxed or not in
extension. At rest, the toe has a variety of articular
capabilities, and has been preserved in many
positions, especially folded over the metatarsals in
several Solnhofen specimens of "rhamphorhynchoids".
The toe has been suggested as a sort of stilletto
"high heel" for support of a semi-plantigrade pes
(considering dimorphodontids had phalangeal-metatarsal
articulations that could not extend into a digitigrade
stance), a "hallucial" grasping toe, or simply folded
when not in use for flight. There are tests that need
to be done on the aerodynamic ability of the hindlimbs
when flying pterosaurs do their thing, that have not
been done.

  Boy, I would have loved to have been there now in
the Late Jurassic German skies....

=====
Jaime "James" A. Headden

  Dinosaurs are horrible, terrible creatures! Even the
  fluffy ones, the snuggle-up-at-night-with ones. You think
  they're fun and sweet, but watch out for that stray tail
  spike! Down, gaston, down, boy! No, not on top of Momma!

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