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Re: Forward Pointing Teeth

On Thu, 7 Nov 1996 martin@hpentccl.grenoble.hp.com wrote:

> Nick Longrich wrote:
> >     Recall also that the VERY front two teeth on the lower jaw
> > actually point FORWARD which is a feature seen in many rhamphorhynch,
> > plesiosaurs, etc. In pretty much every other meat eater they all go
> > backward! The condition is not as extreme as in rhamphorhynchs or
> > plesiosaurs, but it is there to a degree, and it isn't seen in modern
> > carnivores.
> and I'm not fully convinced that these forward pointing teeth in 
> rhamphorhynch 
> _do imply fish eating. I mean, ok you manage to spear a fish with your pointy 
> front teeth, but then what? How do you get it into your throat from there? 
> It's 
> effectively prevented from descending the gullet by the very design of the 
> teeth! You've got to stop, drop it (still wriggling and trying to escape) 
> somehow pick it up (in flight, presumably), and then somehow toss it in the 
> air 
> maybe, and catch it and swallow it. And all this time, other sensisble fish 
> catchers are having no problem 'cos they have backward pointy teeth. 
> Discrepancy 
> of interpretation or or what?

        They have found fish scales in the belly of a rhamphorhynch- I
think it had big forward-pointing teeth and tricuspid teeth in back to
puncture heavy scale. Some plesiosaurs had this to varying degree.
Liopleurodon has forward pointing teeth (a shortneck- I don't know what it
ate) Elasmosaurus has it a little in the forward teeth. I can't find good
pictures, though. 
        Try picturing this- you've got a mouthful of teeth all nicely
lined up in the vertical plane, and you go to make a quick jab at a fish,
but the teeth tend to strike the fish with their forward edges, rather
than the tips. The best way you can get the fish is by waiting for it to
pass into the mouth at the exact moment and then snap down on it. 
        Now, it's easier if you just rotate the teeth forward- then you
just impale your prey, and then you close. Just spear the darn things. To
swallow or carry it in the mouth- just give the head a little toss and
open enough to let the fish slide back into the rear of the jaws, which
are lined with smaller, conical teeth that are nicely alingned straight up
and down.  
        So I think that perhaps you should find teeth pointing forward
heavily when an animal makes a sharp jab at it's prey items- as may have
been the case in Rhamphorhynchus. It seems to me that a porpoise skull I
saw had the teeth sticking slightly out to the sides, so I wonder if they
grab their food from the sides of the mouth (anyone know?). How do
gharials stack up? Do their teeth stick out to the sides at all?

        nick l.