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Re: Quetzalcoatlus could not jump into the air



"With Hang gliders (and I fly them, and in terms of wingspan and weight, they 
seem most similar in specifications to the animals we are talking about here), 
under the right conditions, you need only face into the wind, and raise your 
angle of attack to takeoff (or saunter two steps forward)."

I am a little out of touch with hang-glider masses, but don't they weigh 
something like 20-30 kg? If most folks weigh between 70-80 kg, the combined 
pilot+hanglider mass will fall well short of a likely mass for a giant 
azhdarchid, perhaps almost by half. Masses of over 200 kg are being argued as 
likely for these animals by a number of researchers for a long list of reasons. 
Hence, I'm not sure giant azhdarchids could readily employ hang glider takeoffs 
in the way you suggest. Also, note that giant azhdarchid anatomy is entirely 
consistent with active, powerful, and flapping flight. Soaring and gliding were 
probably employed at times, but there is no reason to think they were passive 
gliders.

You're observation that the longevity and widespread nature of the azhdarchid 
lineage argues against the need for pterosaur 'airports' is a fine one. 
Azhdarchids seem to be the longest lived lineage of all pterosaurs, and are 
found all over the world, presumably reflecting occurances in very different 
topographic and climatic settings. This may be why, under the quad launch 
model, they seem so darned effective at becoming airborne.

Mark

--

Dr. Mark Witton
www.markwitton.com
Lecturer
Palaeobiology Research Group
School of Earth and Environmental Sciences
University of Portsmouth
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PO1 3QL

Tel: (44)2392 842418
E-mail: Mark.Witton@port.ac.uk

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>>> Erik Boehm <erikboehm07@yahoo.com> 11/8/2012 9:31 PM >>>
--- On Thu, 11/8/12, Mark Witton <Mark.Witton@port.ac.uk> wrote:

> From: Mark Witton <Mark.Witton@port.ac.uk>
> Subject: Re: Quetzalcoatlus could not jump into the air
> To: "dinosaur@usc.edu" <dinosaur@usc.edu>
> Date: Thursday, November 8, 2012, 11:29 AM
> "Dumb question:  This abstract
> assumes a downstroke would have been
> necessary for takeoff.  Is it possible that under the
> right conditions
> simply opening the wings at the right angle and facing into
> the wind
> could have gotten the animal high enough for a full wingflap
> without
> much muscular effort?"
> 
> Probably not, assuming the animals weren't the 70kg, eating
> disorder-ridden individuals that Chatterjee et al. make them
> out to be.


I'm going to have to disagree with this... they key words being "under the 
right conditions"
With Hang gliders (and I fly them, and in terms of wingspan and weight, they 
seem most similar in specifications to the animals we are talking about here), 
under the right conditions, you need only face into the wind, and raise your 
angle of attack to takeoff (or saunter two steps forward).

The question in my mind is... were these "right conditions" prevalent enough to 
make this a workable lifestyle that spread across continents and prevailed for 
over a hundred million years.
The lack of practicality is what prevents hanggliding from becoming more 
widespread - it is perhaps too hard to find places suitable to launch them  
-granted pterosaurs had the advantage of the ability to flap for powered 
flight, presumably making them more than capable of level flight in still air - 
which would expand the launch-able conditions and geography.

So "under the right conditions" unpowered standing launches are clearly 
possible - but if this was the only method available to such a creature, that 
would mean that if they ever found themselves on ground with no spot in the 
vicinity that does not have a significant wind blowing up a significant slope 
(lets say no more than 30 degrees cross) - then they might as well be a beached 
whale, and I would not expect such a creature to survive more than a few 
generations, let alone millions of years across the globe.

Unless we take a more "radical" approach, and consider that these large 
creatures were more at home on the ground than in the air, but retained 
"hangglider-like" soaring capabilities - then if we assume the warmer climate 
was more conducive to thermal generation, then periodic long "XC" flights may 
simply have been a long distance travel technique - 
ie, you forage on the ground in some area for an amount of time, and when its 
time to find new foraging grounds, you climb to the top of the nearest 
elevation, wait for the right wind cycle, and launch, and then thermal and fly 
for perhaps hundreds of miles, and arrive at the next foraging area...

There are similar XC contests with para-gliders (which are more practical to 
hime with, and can land in smaller areas than HGs, but don't have the same 
glide performance as a hangglider) - where pilots will hike up to a mountain, 
then launch in the afternoon and often fly hundreds of kilometers, land, sleep, 
and repeat the next day.
In the right places (such as the alps) in the right weather (ie at certain 
times of the year), a paraglider allows one to travel much farther and faster 
than on could on foot, without powered flight or powered launches at all.
I still have my doubts that such a niche is viable.
The question is not "is it possible to fly like that?"
But rather "Is an organism that flies like that likely to reliably survive and 
reproduce?"