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Re: Quetzalcoatlus may have lived like a giant stork




----- Original Message ----- From: "Michael Habib" <mhabib5@jhmi.edu>
To: <jrccea@bellsouth.net>
Cc: <dinosaur@usc.edu>
Sent: Sunday, September 23, 2007 8:24 PM
Subject: Re: Quetzalcoatlus may have lived like a giant stork



True, good point. Just the same, the overall span seems a bit reduced relative to mass in comparison to other large pterosaurs, as best I can tell. The aspect ratio is still high, but not of the grade of some other large pterosaurs (ornithocheirids and pteranodontids being the obvious examples), so I still suspect that there is some adaptation to reduce the inertia of the wing.

From memory without stopping to look it up, I think we're talking about a
difference of approximately 19 vs. roughly 17 (9%). Not anything to write home about. The individual animals can vary the aspect ratio by more than that percentage at will. I believe the difference may be largely due to the severe reduction of the length Ph IV-4 in Quetz, and I expect that may have more to do with heavily loaded animals protecting the outermost wing during flapping contacts with substances other than air than it does with reducing inertia. For example, if reducing inertia were the total goal, then one would expect to see no roach, as roach substantially increases 'added mass' effects due to the additional mass of outboard air swept during the flapping cycle. So, if we anticipate roach (I don't), then we are at least partially forgoing inertia reduction adaptations in general. I find it interesting that Quetz has modified Ph IV-2 and IV-3 to increase the unit spanwise twist in order to compensate for the shorter outboard wing while retaining the ability to resist aftward and vertical bending (the Tee-section, which is really more of a horizontal Y section). Really helps with gust load alleviation (and with thrust production during the flapping cycle).
JimC