Re: Quetzalcoatlus may have lived like a giant stork

[jrc <jrccea@bellsouth.net>]

----- 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