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Re: Dodos, Swifts and Quetzalcoatlus.



On Mon, Nov 10, 2003 at 07:59:03PM -0800, James R. Cunningham scripsit:
> Graydon wrote:
> > > or walking bipedally.  Perhaps demonstrating the same lack of
> > > need.
> > 
> > That's a nearly vertical posture?
> 
> Nineteen feet to the eyes would be.  Eighteen feet to the eyes in a
> quadrupedal posture assumes the spine is oriented about 30 degrees off
> the horizontal (the length from acetabulum to notarium socket is
> estimated to be about 30 inches, or 2.5 feet). So the difference in
> height between quadrupedal and vertical bipedal is about 2.5-2.5*sin30,
> or 2.5-1.25 = 1.25 feet. Not much difference.

Not much at all.

Remarkably like a spider, limb-to-body proportions wise.

> > (I don't suppose there are some stick figure drawings available
> > somewhere?)
> 
> No, but one could be whipped out pretty quickly.  John?  Or, I have a
> schematic scale drawing of a Quetz standing beside a giraffe that I
> did in AutoCad.  Can you read an AutoCad *.dwg file?

I haven't tried, but it's there's a viewer available, so I should be
able to.

I'd certainly be pleased to try!

> > Oh, and is 18 feet from a particular specimen, an expected average, or
> > an upper limit?
> 
> With only one specimen of Qn to work from no one can be sure, and the
> assumption would be that it would be about average.  The 18 feet is with
> the neck placed pretty much vertical to get the eyes about as high as
> possible for peeking about and checking the surrounds (and to compare
> with the bipedal position).  In normal posture, the eyes might be more
> like 16 feet or so off the ground.

Which is still pretty darn huge; "there's a seagull looking in my second
story window" just isn't the sort of news one would generally take
calmly.

> > Somehow, the idea of something that flies so tall that a tyrannosaur
> > couldn't look it in the eye is making the sheer size of the things
> > emotionally real in a way which wasn't previously the case....
> 
> There are at least 3-4 azhdarchid species (one possibly unpublished)
> that approach this size.  Personally, I think slightly larger ones may
> well be found.

Willing to opine on what the biomechanical upper limits to their size
might have been?

> As an interesting aside, should a predator charge one of these beasts
> from any direction other than the front quarter, then by the time the
> pterosaur's hands leave the ground, it is already traveling faster
> than any likely predator would be able to run.  The beasties were
> durned near uncatchable.

I am very much hoping for an approved animation of this launch sequence
to come along someday, so I can find out if the way I'm imagining it my
head is right or not.  (The frustrated predator is optional. :)

It's very cool as an image, the enormous flying thing leaping lightly
into the air, rather than lumbering airborne like a swan.

-- 
oak@uniserve.com | Uton we hycgan    hwaer we ham agen,
                 | ond thonne gedhencan    he we thider cumen.
                 |   -- The Seafarer, ll. 117-118.