Re: Rex jaws

["Thomas R. Holtz, Jr." <th81@umail.umd.edu>]

At 01:26 PM 6/4/99 -0400, Patrick Norton wrote:
>_T. rex_ (and most toothed theropods, for that matter) had a "wrap-around
>overbite": the whole upper surface of the lower jaw fits within the   
>inside
>of the lower jaw. <
>
>That arrangement may have allowed the animal to simply break long bones   
>by chomping on them rather than cutting or gnawing them as do mammalian   
>carnivores with occlusal teeth.

Although it may have *allowed* robust-toothed tyrannosaurs like _T. rex_ to
do some long bone chomping, the wrap-around overbite of theropods is a very
primitive feature, going way back to early archosauriforms.

In these animals, and indeed in the majority of toothed theropods, the teeth
are narrow and ziphodont (blade-like), the skull is hatchet-shaped, and
there is no ossified secondary palate.  In these forms bone-crunching is
unlikely to have been a major aspect of their feeding: their skulls and
teeth would not be well able to absorb the non-vertical forces exerted by
tooth-bone contact.

Most of these animals probably didn't do much in the way of bone munching,
but stuck with the flesh, viscera, etc.

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:tholtz@geol.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661