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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
Tel: (44)2392 842418
>>> David Peters <firstname.lastname@example.org> 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