Re: ornithomimes and herbivory

["King, Norm" <nking.ucs@smtp.usi.edu>]

The subject question has come up recently, and I'll add this observation:

In many (all?) ornithomimes the jaw joint is offset below the jaw line, 
similar to the design in sauropodomorphs and ornithischians.  This causes 
the jaws to close more or less simultaneously along their entire 
length--good for chewing.  In contrast, definite carnivores have a 
scissor-like jaw closure, with hinges at much the same level as the line 
(plane?) of jaw opening (there must be a better way to say that).

Might that also suggest ornithomime herbivory?

Opposing that interpretation is the sleek abdominal profile of 
ornithomimes.  Herbivorous dinosaurs, as I put it, had beer bellies.  
Perhaps ornithomime diets were similar to those of ostriches--they eat 
only the choicest parts of plants, rather than a lot of rough greenery.  
Don't they also eat grubs and other forms of "meat" when they can?  
Cassowaries do.  If ornithomime diets were similar, they wouldn't need 
such extensive digestive systems as most herbivores.  Of course, that 
would make them omnivores.

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Norman R. King                                       tel:  (812) 464-1794
Department of Geosciences                            fax:  (812) 464-1960
University of Southern Indiana
8600 University Blvd.
Evansville, IN 47712                      e-mail:  nking.ucs@smtp.usi.edu