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SVP ornithopod thoughts (was RE: Horns and Beaks: New taxa and descriptions)

> From: owner-DINOSAUR@usc.edu [mailto:owner-DINOSAUR@usc.edu]On Behalf Of
> Tim Williams
> Sent: Wednesday, November 08, 2006 3:36 PM
> To: dinosaur@usc.edu
> Subject: RE: Horns and Beaks: New taxa and descriptions
> >Brill, K., and K. Carpenter. 2006. A description of a new ornithopod from
> >the Lytle Member of the Purgatoire Formation (Lower Cretaceous) and a
> >reassessment of the skull of Camptosaurus; pp. 49-
> >67 in K. Carpenter (ed.), Horns and Beaks: Ceratopsian and Ornithopod
> >Dinosaurs. Indiana University Press, Bloomington.
> >
> >Describes Theiophytalia kerri, erected for the partial skull YPM 1887,
> >which is the specimen used by Marsh to restore the skull of Camptosaurus.
> The name _Theiphytalia_ translates as "Garden of the Gods", a reference to
> the site.
I haven't seen the volume yet (other than a quick glance at a xeroxed proof), 
but the above reminds me of something that came up as
the result of a couple of talks at SVP.

1) Scheetz et al.s presentation on the new, complete skull of _Camptosaurus_. 
This is the first relatively complete skull associated
with definite _Camptosaurus_ postcrania, and shows that it was more 
plesiomorphic, triangual, and "_Dryosaurus_-like" than
previously thought. The elongate, rectangular, '_Iguanodon_-like" skull we all 
know is actually from isolated material (the
aforementioned YPM 1887), and may belong to a different taxon. (As Brill and 
Carpenter have apparently done!)

2) Padian et al.'s examination of the histology of basal ornithopods, and their 
observation that no _Dryosaurus_ specimens so far
examined show adult features. So what does an adult _Dryosaurus_ look like? Not 
actual _Camptosaurus_, since postcrania of the two
do overlap in size and are disctinctive. Given that juveniles tend to look more 
basal phylogenetically than their adult stage, adult
_Dryosaurus_ might concievably be more "_Iguanodon_" like.

So perhaps _Theiphytalia_ shows us what adult dryosaurids look like!

                Thomas R. Holtz, Jr.
        Senior Lecturer, Vertebrate Paleontology
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
        Mailing Address:
                Building 237, Room 1117
                College Park, MD  20742

Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796