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RE: Long Horizontal Necks Re: Vertebrae of Early Sauropods



--- Eric Martichuski <herewiss13@hotmail.com> wrote:
> >From: Mark Hallett <marksabercat@yahoo.com>
> >To differ with you on this, Eric, why would walking
> be
> >more stressful for a sauropod than swinging its
> head?
> >Are you speaking here of caloric expenditure when
> you
> >say "stress"? Moving towards a standing food source
> >consumes only a trivial amount of an animal's
> energy
> >(even less for large animals,which although their
> >absolute caloric expenditure is greater than a
> small
> >animal's, is less in proportion to their size).
> 
> I was thinking more along the lines of spikes in
> blood pressure, but caloric 
> expenditure works as well.  In order to move from
> one clump of foliage to 
> another, the sauropod can either
> 
> A) move it's entire multi-ton bulk...and then do it
> again for the _next_ 
> clump, and the one after that; all of which engages
> a large number of 
> muscles and puts added strain on bones, tendons,
> etc.
> 
> or
> 
> B) move its much lighter (relatively) neck...and
> this movement can suffice 
> for a great many clumps of foliage before a step
> needs to be taken.  In 
> contrast, think about how much movement the _entire_
> body of, say, a zebra 
> would have to undergo to graze through as much plant
> life as a single 
> neck-sweep would cover.
> 
> Obviously, the sauropod is taking a lot of steps
> anyway (i.e. all the 
> trackways we have, etc.), but given that it
> _appears_ to be living close to 
> design limits in a number of ways, it only makes
> sense to reduce the strain 
> on those limits when possible.
> 
> I'd actually thought this feeding strategy was
> already accepted as a given 
> for some species.  Obviously much less connected to
> current thinking than 
> I'd assumed. ;-)
> 
> I do accept your other statements without quibble,
> however. ;-)
 
Oh no, don't do that, since I and others might be
eventually proven wrong! You're obviously putting a
lot of good, original thought into this problem.
Mike's points about the enegy costs re: long necks
make sense however, and I agree with him about this.
So far I think that Stevens and Parrish's computerized
investigations support the idea of a horizontal/low
subvertical "neutral" pose for the necks of
diplodocids, but this wouldn't preclude the ability to
use the neck in a vertical position-- in fact the
extreme ventriflection ranges they determined for
these sauropods fit in well with movements that would
facilitate feeding from this posture, as well as the
much more acute articulation of the skull with the
atlas vertebra in these taxa. --Mark Hallett
>
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> And no other hope for us
> But that we grow wise. -- Diane Duane
>
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