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Re: Quetzalcoatlus may have lived like a giant stork



----- Original Message ----- From: "Brandon Pilcher" <trex_kid@hotmail.com>
To: <dinosaur@usc.edu>
Sent: Friday, September 21, 2007 8:19 AM
Subject: Quetzalcoatlus may have lived like a giant stork



Morphological details include a jaw shape that was long but lacked adaptations suitable for skimming, and proportionately longer legs and shorter wings (implying that they walked on the ground more than other pterodactyloids and were less specialized for spending a very long time in the air). I don't know that much about pterosaurs, but I find his argument very compelling. It's worth reading despite the technical jargon.<

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Placing the bones of the neck in their extreme deflection limits in the dorso-ventral and lateral directions demonstrates that the ventral and lateral mobility of the Quetz neck is limited to an extent that makes the stork analogy highly unlikely. Since it can't bend its neck like a stork, I doubt that it lived like one. Nor would it be suitable for a heron niche -- since anything that requires a 'strike' capacity is out.

The Quetz jaw contains specializations that ARE suitable for skimming (but not deep nor particularly continuous submergence). The animal would not have been suited to skimming in rynchops mode, but there is no reason why it should have used that mode. It was also not suited to 'tuck & pluck' aerial feeding. But it does have specializations that would have been both suitable and desirable for other skimming modes. That said, I do think that if it spotted something tasty and relatively immobile while strolling along, it would gobble it up -- most creatures would (me included -- I graze a lot when around picnic tables). I would expect Quetz to feed off the ground or lake bed on days when the weather wasn't suitable for flying.

The Quetz wing skeletal structure is well suited for extracting energy from lakeshore effects and from microlift and cloudstreets as well as thermals -- much as sailplanes of similar size and loading do. It is not optimised for offshore marine flight (but then, most of the known specimens were found a couple of hundred miles inland from the seashore, so that isn't exactly surprising).

The wing is about as good aerodynamically as that of an albatross, though the animal as a whole was draggier than an albatross because of the larger head and neck. I would not though, expect Qn or Qsp to spend more than say 6 to 10 hours a day airbourne. So, for Qn an approximate range of about 360 to 600 miles per day when traveling, or local flights of perhaps 250 to 300 miles when loitering in one area. For the same time spent in the air, the distance numbers for Qsp would be roughly about 15% less. Note that weather patterns would be expected to limit the need for more than about 600 miles of straight-line range per day anyway.

Both size varieties of Quetz are far more powerful flappers than other pterosaurs, but they are not suited for long periods of continuous flapping. In fact (due to neck length), I'd expect duration of continuous flapping to be less than one minute, more likely about 30 seconds (enough duration to flap about half a mile and then glide another quarter mile in no-lift conditions). So, depending on weather, the animals could travel anywhere from three quarters of a mile to about a quarter of the way across the continent without having to land. That isn't much of a limitation -- it's simlar to many of today's general aviation aircraft and better than some.

Also note that when I set the lengths for the hindlimbs on Matt Smith's full-scale Qn skeletal sculptures, I gave them an allometric lengthening factor of 2.27 to give the Qn torso and neck a terrestrial posture roughly similar to Qsp. I set the neck and torso lengthening at a factor of 2.06 (the unscientific arithmetic average of the humerus and r/u ratios between Qn & Qsp -- we were in a hurry to make the deadline for the opening of the TMM). Also, the scapulocoracoid in the Qn sculptures looks nothing like the real thing would, and the head is an isometric 2.06 blowup of a Qsp head. It is about a foot shorter and far more gracile than I would expect an actual Qn head to be. What I'm saying is that those Qn sculptures were intended as an entertaining visualization, not to be used for scientific research.
All the best,
JimC