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Heterodontosaurs, etc. (was Re: Echinodon)

At 04:20 PM 9/5/97 -0400, Dinogeorge wrote:

>I classified _Echinodon_ as a basal heterodontosaurian in my Gakken article
>way back in 1993 or so. But it has a different pattern of premaxillary and
>dentary fangs, so it should lie outside Heterodontosauridae +
>Marginocephalia. Same holds for the small Fruita "Echinodon" (it's gotta be a
>new genus) whose jaw is illustrated (thanks to Dinamation's George Callison,
>who presently has the specimen) in that article.

Went back to check that one (Fig. 14, p. 79 of Dino-Frontline 8, October
1994). (As you might guess, I keep the complete run of Gakken's Kyoryugaku
Saizensen (aka Dino-Frontline) on my desk...)

>The notion that heterodontosaurids might be basal marginocephalians goes back
>at least to Zhao's 1983 paper in _Acta Pal. Polonica_--the one wherein he
>introduces all kinds of nomina nuda. That part made a great deal of sense to
>me when I read it.

I hope that they get around to describing those new forms from that paper,
they sound interesting (and I, too, think a lot of it makes sense).  Having
never seen the actual data matrix to support the ornithopod position of
Heterodontosauridae (which hasn't been published), I would not be terribly
surprised if they didn't turn out to be basal members of the
marginocephalian line.  (Then again, they may very well be in the proper
place as is).

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