Re: Dodos, Swifts and Quetzalcoatlus.

[david peters <davidrpeters@earthlink.net>]

-----Original Message-----
From: "James R. Cunningham" <jrccea@bellsouth.net>
Sent: Nov 10, 2003 10:37 AM
To: davidrpeters@earthlink.net, dinosaur@usc.edu, 
        michael@paleoproductions.fsnet.co.uk
Subject: Re: Dodos, Swifts and Quetzalcoatlus.

David Peters wrote:
> 
> so the forelimb minus the folding wing finger
> has to more or less equal the hindlimb minus the pes. It's something of
> a constraint on their engineering, I suppose, to keep the proximal
> elements related in size.

Not true in Quetz.  

>>>>> I wasn't thinking linearly, Jim, but as you say, elbow bent.

If you take the forelimb minus the folding
wingfinger, raise the humerus dorsally, then bend the elbow back
downward so that the elbow becomes the 'highest' point, THEN the length
is more or less equal to the hindlimb minus the pes.  Note that the
Quetz scapulocoracoid, humerus, and proximal r/u are structurally
modified to support this position without substantial muscular effort
and that synovial sac markings at the joints are consistent with it.  I
don't know how much of the time it was actually used.

>>>>Maybe while resting, since this position is supported without muscular 
>>>>effort. Time used: all night long.


> In the exceptional pteros, such as
> Nyctosaurus, Pteranodon and some ornithocheirids, where the proximal
> forelimb elements greatly exceed the hindlimb elements, then elbow
> bending effectively reduces the forelimb length,

This is true for Quetz as well.

> or, as Chris Bennett
> has shown, the pterosaur simply lifts its oversized forelimbs up and
> walks bipedally.

For some of the larger pterosaurs, this would appear to be unlikely in
the extreme.  An animal that can walk around stablely (sp??) in
quadrupedal posture with its eyes 18 feet in the air doesn't have much
need to rear up and walk unstablely on its hind legs just so its eyes
can reach 19.5 feet into the air.  

>>> Except when its ready to hump something 

As an aside, giraffes have relative
neck and leg lengths that are somewhat reminiscent of the big azhdarchid
pterosaurs, and very few giraffes spend much time in bipedal position,
or walking bipedally.  

>>>> ditto.

Perhaps demonstrating the same lack of need.

All the best,
JimC