Basal ornithischian evolution (was RE: Prosauropods)

["Thomas R. Holtz, Jr." <tholtz@geol.umd.edu>]

> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Brent Jones
>
> As an aside of the whole "which came first..."
> question, what is the latest thinking on the
> ornithiscians? Did they evolve as plant eaters first,
> then evolve the different hip structure to help digest
> the tough plants?

The (admittedly incomplete) type of Pisanosaurus, arguably the most
primitive and one of the oldest ornithischians, shows what appears to be a
forward pointing pubis.  However, it has a predentary (evidenced by the
facet on the dentary) and teeth associated with herbivorous diet.  This
suggests that plant-eating evolved first, and opisthopuby second.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
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