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Re: Sauropod Trunks

MGibb21521@aol.com wrote:
I just joined this list...
I was wondering what anyone's input on the concept of sauropods having trunks
If you examine a _Brachiosaurus brancai_ skull, you can see deep grooves
coming down from the nostrils to the snout.  This can also be observed in
_Nemegtosaurus_, _Antarctosaurus_, and _Diplodocus_, among others.  Also, what
would be the purpose of nostrils high on the head besides a trunk; we know
that the large sauropods were not highly dependent on water as once thought...
A trunk (or a 'snout', like on a swine) on a sauropod could help it eat more
efficiently and make it easier for the animal to remove vegetation from trees.


  I have heard this theory before.  I also read somewhere (i can't remember where, it was too long ago) a refutation of it (the points of which I have since forgotten... d'oh!)

I suppose the two arguments against sauropod trunks are

(1) no known living archosaur (reptile or bird) has the required facial muscles
(2) please correct me if I am wrong here - no trace of forama for necessary blood vessels have been found in the sauropod snout or cheek region

A better explanation which I read in another paper (again - apologies for lack of refences - it was part of the ectothermy-endothermy controversy that was raging some years back) is that the dome-like skulls on these creatures allowed blood to pool in that area and hence stop the brain from overheating, which would have bene a  real problem in endotherms of that size.

I later read something else that was interesting.

J.S.McIntosh writes
"Additionally, sauropods may well have had a carotoid sinus that served a sa  reservoir of arterial blood to perfuse the brain when the caratoid arteries collapsed due to insufficient systolic pressure during high feeding"
ch.16 - Sauropoda
in Weishampel, Dodson, & Osmolska, eds, _The Dinosauria_, 1988,

When I read the above it made me think that, assuming a gigantothermic rather than endothermic metabolism of adult sauropods, the reservoir of blood would be to supply oxygen to the brain during periods of anoxia when the neck was held erect.  (or the blood may well have served both purposes).

Anoxia must have been a  real problem for sauropods.   We know for example how difficult it is for a  giraffe to pump blood to it's head against the force of gravity.  How much more so for a  creature that could hold it's head so much higher?  This is a very good argument *against* Bob Bakker's & Greg Paul's giraffe-like barosaurs & mamenchosaurs.  Another argument against giraffe sauropods is that their cervical vertebrae could not have supported the muscles required to hold the neck up stiffly.

"No sauropod has elongated neural spines at the base of the neck which could provide leverage for epaxial muscles for sustained elevation of the neck in a  giraffe-like manner"
J.S.McIntosh _Ibid_ p.404

More likely is that the neck was held out more or less horizontally in front of the body & would sweep over the vegetation, allowing the little head to browse.  Occaisonally the beast would rear it's neck up & grab leaves and branches from tree tops, & when that happened it would be impossible for the heart to pump oxygenated blood up to the brain.  In those instances the blood stored in the dome-like top of the head would provide oxygen for the short time required. 

Kewl!   :-)

M.Alan   Proteus   CyBeRrDeWd

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