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Re: was: Pterosaur.net now: pteroid



Comments inserted.
JimC

----- Original Message ----- From: "David Peters" <davidpeters@att.net>
To: "Augusto Haro" <augustoharo@gmail.com>
Cc: "jrc" <jrccea@bellsouth.net>; "Mark Witton" <Mark.Witton@port.ac.uk>; <pterosaur.net@googlemail.com>; "Mike Habib" <habib@jhmi.edu>; "dinosaur mailing list" <dinosaur@usc.edu>
Sent: Friday, January 15, 2010 1:19 PM
Subject: Re: was: Pterosaur.net now: pteroid


That facet Chris and Jim are looking at on the preaxial carpal is not the facet for the articulation of the pteroid.

Then why (in the specimen that I'm looking at) is its 'footprint' such a perfect match for the shape of the base of the pteroid?

Okay, next subject, pteroid depression.

The pteroid-radiale joint permits all sorts of movement

But not when mounted in the facet that Chris and I prefer. I'm not going to speak for Chris though -- he's more than capable of doing that for himself. In the specimen I have, the pteroid articulation is capable of substantial swing along the camberline and limited swing transversely to it -- which, by coincidence, is exactly what you would expect from it.

-- in the absence of soft tissue. Add soft tissue and an airstream and its a different story. The tension at the leading edge of the propatagium restricted all movement at the pteroid tip.

Er uh, why? Tension on the leading edge would provide essentially zero force to inhibit deflection of the pteroid in any direction until the deflection becomes fairly substantial. It's much the same as the vector situation of a rope between a tree and a vehicle bumper with someone shoving sideways on the rope at its middle. The rope tension does not inhibit initial lateral movement -- in fact, that initial lateral movement is used to create even more tension.

So what does that leave us? A pteroid that can rotate at its base, not like a swinging compass needle (in anterior view while flying), but like a radius/ulna. The whole pteroid could move up and down, never NOT pointing to the deltopectoral crest, but always parallel to its original orientation.

And what purpose would that serve?

That work for you guyz?

No.

JimC