[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: was: Pterosaur.net now: pteroid
Palmer and Dyke (2009) had no qualms with the pteroid being depressed to change
the camber of the wing, and they were specifically testing the bending strength
of the pteroid. Bennett (2007), by the way, suggests that the pteroid muscle
was anchored on the preaxial carpal and cites evidence for such a muscle on
both Pteranodon and Nyctosaurus. It seems to me, therefore, that the weight of
evidence indicates that the pteroid was both capable of depressing the
propatagium and biomechanically sound enough to do so.
Dr. Mark Witton
Palaeobiology Research Group
School of Earth and Environmental Sciences
University of Portsmouth
Tel: (44)2392 842418
>>> David Peters <firstname.lastname@example.org> 15/01/2010 14:04 >>>
Okay, given the grooves, and given the muscles attached to the grooves, which
bone did the other end of the muscles attach to and does that attachment
provide a ventral vector when pulled? Most reconstructions place the pteroid
anterior to the radius while in flight.
So... if the pteroid is [somehow] pulled ventrally, how does that affect the
sometimes sharp tip that WAS pointing at the deltopectoral crest? Does that
produce a V-shape (in anterior view) in the propatagium? And if so, doesn't
that put a lot of stress on that fragile point?
I see the anterior propatagium as a straight line providing an inboard leading
edge to the wing. It changes shape only when relaxed, when the elbow is flexed
during wing folding, as in birds and bats. Those grooves, in my opinion,
anchored the pteroid to the rest of the wrist because there was precious little
else to anchor it at its articular surface.
On Jan 15, 2010, at 7:46 AM, Mark Witton wrote:
> There are grooves and rugose protuberances on the proximal ventral surfaces
> of pteroids (see Unwin et al. 1996) : these, presumably, anchored musculature
> that, because of its insertion on the ventral pteroid face, would have to
> depress the pteroid if contracted.
> Dr. Mark Witton
> Palaeobiology Research Group
> School of Earth and Environmental Sciences
> University of Portsmouth
> Burnaby Building
> Burnaby Road
> PO1 3QL
> Tel: (44)2392 842418
> E-mail: Mark.Witton@port.ac.uk
>>>> David Peters <email@example.com> 15/01/2010 13:27 >>>
> What tells you the pteroid can be depressed? Which muscle depresses the
> pteroid? What bone anchors that muscle? There's nothing out at the tip to
> pull it up and down. If you're attempting to manipulate the pteroid near its
> articulation, then you've got a very short lever to work with. And finally,
> are you articulating the pteroid principally on the radiale?
> At present, your answer doesn't appear to have any evidence to back it up.
> On Jan 14, 2010, at 1:28 PM, Mike Habib wrote:
>> On Jan 14, 2010, at 11:42 AM, David Peters wrote:
>>> "The additional membranes (especially the front one) controlled by a
>>> special bone called the pteroid would have helped with steering." The
>>> pteroid was inboard and would not have been such a great steering aid.
>> Because depression of the pteroid (and hence the propatagium) changes entry
>> angle of the inboard wing, the pteroid would be a very good "steering aid" -
>> flying taxa turn by altering the fluid force production between the two
>> wings, such that they differ, which forces a roll and therefore a turn. A
>> little change in entry angle goes a long way, so the propatagial position
>> is, in fact, a factor in maneuverability.
>> Michael Habib
>> Assistant Professor of Biology
>> Chatham University
>> Woodland Road, Pittsburgh PA 15232
>> Buhl Hall, Room 226A
>> (443) 280-0181