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Re: CRETACEOUS VARANIDS



At 07:16 AM 12/9/97 -0600, Toby White wrote:

>>got virtually no mammalian carnivores). This theory, nice as it is, 
>>has been invalidated by the large number of Australian marsupial 
>>carnivores described in recent years: new dasyuromorphs, carnivorous 
>>macropodids and thylacoleonids a-plenty.
>
>I get the impression that mammals change dietary habit quite easily, whereas
>dinosaurs (AFAIK) have made the transition only twice, both times from
>carnivore to herbivore (unless one includes birds).   Furthermore, I've
>never heard of a dinosaurian omnivore.  Perhaps they exist, but it doesn't
>seem to have been a common habit.  Is there a simple explanation for this
>pattern?

Yes, but I think it has to do with dinosaur paleontologists rather than with
dinosaurs.  That is to say, a lot of people seem to assume "Theropoda =
strict carnivore, everything else = strict herbivore."

On the other hand, omnivory or herbivory has been suggested for
therizinosauroids, oviraptorosaurs, ornithomimosaurs, and troodontids among
the non-avian theropods, and omnivory for basal sauropodomorphs
("prosauropods") and ceratopsians among the traditional "herbivores".  We
could discuss the various evidence used to support these hypotheses, if you
wish.

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:th81@umail.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661