Re: was: Pterosaur.net now: pteroid

["jrc" <jrccea@bellsouth.net>]

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