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Re: Quetzalcoatlus could not jump into the air

Guess I should have been there!  Honestly, kind of nifty that someone threw 
down the gauntlet at a meeting. I feel so official!

Unfortunately, this looks like the argument comes down to "but we got a 
different answer in 2004!" Yes.  We know, and for five years I've explained why 
it is probably wrong.  Oh well.

What's really amusing is that the numbers (presumably by Alexander) are quite 
good; they just don't lead to the conclusions of the abstract!  A 3 meter leap 
is more than sufficient for flapping clearance in a giant pterosaur (we can get 
the amplitude from a two-equation system easily enough).  And while the power 
gap may seem large, note that the extra 800 Watts needed comes down to a mere 
2.05 kg of avian grade fast twitch muscle (or 2 kg croc grade).  That's a 
trivial margin of difference for a reconstruction of an animal that size, 
especially given they only give the creature 75 kg of total mass to work with 
(making it mostly air) while the model they seek to refute adds an extra 175 
kg, much of which is in the limbs.

Still, kinda pumped to have an academic debate on this.  Bring it on Chatterjee 
and Alexander!


--Mike H.

Sent from my Cybernetic Symbiote

On Nov 8, 2012, at 8:53 AM, Ben Creisler <bcreisler@gmail.com> wrote:

> From: Ben Creisler
> bcreisler@gmail.com
> A talk at the GSA meeting and a new story:
> https://gsa.confex.com/gsa/2012AM/finalprogram/abstract_205827.htm
> CHATTERJEE, Sankar, Geosciences, Texas Tech University, 3301 4th
> Street, Lubbock, TX 79409-3191, ALEXANDER, David E., Ecology &
> Evolutionary Biology, University of Kansas, 2041 Haworth Hall, 1200
> Sunnyside Avenue, Lawrence, KS 66045, and TEMPLIN, R. Jack, 2212 Aster
> Street, Ottawa, ON K1H 6R6, Canada, jtemplin@rogers.ca
> Large pterosaurs could takeoff from an elevated perch by diving into
> the air to initiate flight, but to take off from level ground was
> arduous. Our estimated mass of the giant Quetzalcoatlas from the Late
> Cretaceous Big Bend National Park of Texas is about 70 kg, which is
> close to the theoretical upper mass limit for a flying animal.
> Quetzalcoatlus could run bipedally downhill to pick up flying speed, a
> technique used by albatrosses and hang glider pilots. It has been
> proposed recently that Quetzalcoatlus with a new calibrated mass of
> 250 kg was capable of initiating flight directly from the ground using
> forelimbs as a catapult similar to the style of common vampire bat (~
> 25 g). One issue is scaling. What is possible for a lightweight bat
> appears impossible for a 10,000 times heavier pterodactyloid, which,
> due to surface-to-volume ratios, will have approximately 0.01 times
> the muscle force per unit mass of the bat. Another is the height
> achieved by such a “pole-vault:” the maximum ballistic jump height of
> 2 to 3 meters would not be high enough to allow a significant
> downstroke, where most lift and thrust is produced. With a wingspan of
> 10.4 m, Quetzalcoatlus would not have been able to flap vigorously for
> lift generation from such a jump without smashing its delicate wings
> on the ground. Moreover, the animal would need about 2440 watts to fly
> level after jumping; the estimated maximum mechanical power available,
> however, even with a few seconds of maximal anaerobic muscle
> contraction, was approximately 1600 W, far below the flying speed that
> would result in crash landing. Indeed, the body mass of 250 kg itself
> appears to be largely overestimated, as powered flight and ground
> takeoff seem unlikely for an animal that heavy.
> 2012 GSA Annual Meeting in Charlotte
> ====
> news story:
> http://news.discovery.com/animals/flying-dinosaur-pterodactyl-121108.html