Re: Gallery and Commentary for Copenhagen Mamenchisaurus

[Mike Taylor <mike@indexdata.com>]

> Date: Wed, 23 Jun 2004 19:25:56 -0400
> From: DinoBoyGraphics@aol.com
> 
>> Just playing Devil's advocate here (snip), but the vast majority of
>> grazers today are mammals, with big, heavy jaws, teeth, and brains
>> that sauropods didn't have to deal with.
> 
> Despite this, giraffes have long necks, so apparently mammals can
> evolve them under the proper selection regime.

If you want to call that "long", yeah.  But recall that even a really
big giraffe has a neck that's only about 3m long.  This compares with
lengths of 12m or so in some sauropods -- for times as long.  If the
necks are isometrically similar, then the sauropod's is 4^3 = 64 times
as massive as the giraffes, plus its centre of mass is four times
further out from the shoulder so it generates a moment that is 64x4 =
256 times as great as a giraffe's.  Wow.  Those are some big numbers.

Now we all know that in fact sauropod necks are not isometrically
similar to those of giraffes, and that their cervical vertebrae are
very pneumatic, so that figure is no doubt somewhat exaggerated.
Still, to pluck a figure out of the air, it doesn't seem altogether
unreasonable to think that a big sauropod might have a moment about
its shoulder that is a fifty to a hundred times greater than that of a
giraffe.  Which is why I keep going on about how there are no
meaningful extant analogues.

> I can't speak to the publics impression of camarasaur neck length,
> but we have two at the Wyoming Dinosaur Center, and the neck is not
> much longer than is needed to reach the ground (especially with the
> difficulty in lowering the neck with the upward oriented
> cervico-dorsal region...).

Adults?

> Not that the anatomy supports (in this case) grazing, but the
> energetics wouldn'tbe too unfavorable.

(You mean browsing, right?)

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