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Re: Dino gizzards



>I am wondering if gastoliths have been found with any ornithischian=
> dinosaur.  I do know that gastroliths have been confirmed in sauropods, and=
> they do occur in some (most?/all?) birds.  If a gizzard can be shown in=
> theropods as well as sauropods, but in no ornithiscian, would this put the=
> proposed "phytodinosauria" taxon in doubt?

Gastroliths (aka gizzard stones) are an extremely primitive feature of
archosaurs, this behavior being present in both crocodilians and birds.  It
is thus expected of dinosaurs, unless a particular lineage evolved away from
them. As such, the shared presence of this behavior in two or more dinosaur
lineages is a shared primitive character, and the lack thereof is not useful
in teasing out within-dinosauria phylogeny.

The type of the ornithischian  _Psittacosaurus_, in any case, was found with
gastroliths.

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