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George wrote:
>Not quite true of most ornithopods, from hypsilophodontians to
hadrosaurs,
which had multijointed movable jaws and almost certainly some kind of cheeks to keep the food from falling out the sides of the mouth.< True for the movable jaws. However it doesn't
necessarily mean they needed mammalian herbivore cheeks to do the job. Just
shortening the lip-mouth line would help them keep their food inside their
mouth. Recent herbivorous lizards are doing just fine in chewing and digesting
their plant food and there is a lot of similarity between the jaws and teeth of
say hypsilophodonts and iguanas.
On the other hand crocodilians are lipless
(fish-eating specialization: therefore some pterosaurs and some extinct aquatic
reptiles were lipless, too), while most of the other recent reptiles have scaly
lips (so did most of the dinosaurs). Yes, they are differ from mammalian soft,
movable lips, but they are true lips which cover the teeth when mouth is
closed. Certainly, no lips are necessary for drinking
water.
Berislav Krzic
veselinka.stanisavac@siol.net Beri's Dinosaur World http://www.geocities.com/CapeCanaveral/Lab/1638/index.html |