Re: Rex Jaws

[chris brochu <cbrochu@fmppr.fmnh.org>]

All crocodylians have nutrient foramina. All extinct crocodyliforms -
aquatic or not - have them as well.  Sorry - I don't think the foramina
signify lips at all, since they merely channelize branches of the facial
nerve that innervate the skin on the snout and jaw.  

chris


Frank Galef wrote:






> So now I'll toss in my thoughts:
> I have also wondered a lot about this topic.  There has been some waffling
> from the lipless camp, saying that a row of scales covering the teeth are
> not really lips.  Well, I don't say they have to smile or osculate, but if
> it looks like a lip and it smacks like a lip, I would call it a lip.  The
> main function here is water preservation, and oral surfaces provide a lot
> of area to lose moisture.  Something to cover the oral  structures seems
> to be pretty prevalent in terrestrial non-beaked vertebrates, and I think
> beaks seal well too, but they are not covering teeth.  Crocodilians don't
> have lips, but they are mostly aquatic, and does anyone know if they have
> those nutrient foraminae?  I haven't seen them when I've  looked at croc
> skulls, perhaps Chris Brochu has a comment?  While on the subject, what
> about the exuberant gum tissue that is seen in most reptiles?  Teeth are
> usually felt more than seen, even long ones.  I suspect the pink sticky
> covering has something to do with continuously replacing teeth, but I
> haven't been able to find anything about it in most basic reptile
> references.  Any help from the experts here?   When I have looked at large
> theropod skulls, the polished and worn area on the teeth seems to begin at
> a distance from the bone, suggesting that gums were probably there.
> Comments from the Theropod specialists here?
> Frank

-- 
----------------------
Christopher A. Brochu
Department of Geology
Field Museum of Natural History
Roosevelt Road at Lake Shore Drive
Chicago, IL 60605

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