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Re: Quick question for pterosaur aficionados:



I guess you could say phylogeny? Flying animals, as a general rule, flex whatever joints are available to reshape the wing as needed (be it span reduction during flight or folding of the wing "on the tarmac"). For bats, a lot of the motion comes from the digits, while birds have fused digits and therefore rely heavily on wrist flexion, instead (especially for wing folding when not in flight). Pterosaurs don't have any joints fused up in the forelimb, so they're all able to flex to some degree for purposes of folding and span reduction. However, the MC-PH joint of the fourth digit is the most mobile in this regard, and probably did most of the folding. Elbow and shoulder also certainly important, along with the wrist, especially for span reduction in flight.

If they have it, they can use it.

Cheers,

--Mike


Michael Habib
Assistant Professor of Biology
Chatham University
Woodland Road, Pittsburgh PA  15232
Buhl Hall, Room 226A
mhabib@chatham.edu
(443) 280-0181



On Mar 24, 2010, at 12:29 PM, David Peters wrote:

I was more interested in complete folding, like "on the tarmac."
But thanks for that data.

Some of both? Is this phylogenetic? Or happenstance?

David Peters
davidpeters@att.net


Some of both.  Any joints that
can be flexed will help fold the wing.  Most of this
will occur at MCIV-PhIV (outboard), but the elbow can flex,
as can the wrist.  For actual folding, the wing finger
is most important, but it should be noted that span
reduction during flight was likely accomplished more at the
elbow and wrist.  The initial span reduction produces
extra cambering, and so (counter-intuitively) increases the
lift on the span-reduced wing.  Additional span
reduction reduces lift as area shrinks, and then reduces it
a great deal if the wing begins to flutter (this last issue
prevented pterosaurs from utilizing the same degree of span
reduction in flight as birds use).

--Mike


Michael Habib
Assistant Professor of Biology
Chatham University
Woodland Road, Pittsburgh PA  15232
Buhl Hall, Room 226A
mhabib@chatham.edu
(443) 280-0181



On Mar 23, 2010, at 9:33 PM, David Peters wrote:

Wing folding:

Inboard or outboard of the elbow?

You can probably guess what I would say, but I'll
weigh in after others have spoken.

David Peters
St. Louis