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Re: Fwd: RE: ORNITHISCHIANS :-)
Ken Kinman wrote:
> Dear All,
> Tracy asked me to forward the post (down below) to the whole list.
> I was a little surprised at first, but I guess it is a question that
> should be considered. I'm not sure why stegosaurs in particular might be
> classified outside of an ornithischian clade, but if they were, I think
> ankylosaurs would probably have to be classified separately as well.
> I'm not sure, but are you suggesting that the predentary might have
> evolved independently in two or more lines (stemming from different groups
> of primitive dinosauromorphs? I've never really considered that
> possibility----I guess it is possible, but doesn't seem very parsimonious.
> But then again, before last weekend I knew very little about ornithischian
> phylogeny, so I am a relative "newbie" on this subject. Will have to roll
> the idea of a "polphyletic ornithischia" around in my head. But if it is
> polyphyletic, that is kind of scarey. If the interrelationships of just
> three major groups of dinosaurs is problematic, think how messy it would get
> if we had even more independent groups to consider.
> -----Cheers, Ken
> >From: "Tracy Ford" <email@example.com>
> >To: <firstname.lastname@example.org>
> >Subject: RE: ORNITHISCHIANS :-)
> >Date: Wed, 13 Jun 2001 13:20:25 -0700
> >-----Original Message-----
> >From: email@example.com [mailto:firstname.lastname@example.org]On Behalf Of
> >Sent: Wednesday, June 13, 2001 6:01 AM
> >To: email@example.com
> >Subject: Re: ORNITHISCHIANS :-)
> > I wouldn't go so far as to suggest that Thyreophora (sensu lato) is
> >polyphyletic. I have a feeling that it is neither holophyletic nor
> >polyphyletic, but simply paraphyletic (and therefore a natural group for
> >traditional eclecticists). Right now I would say that armor in stegosaurs
> >and ankylosaurs is probably something that is neither pure convergence nor
> >pure parallelism, but something in between (since convergence and
> >parallelism can grade into one another, and distingushing between the two
> >may be next to impossible given an incomplete fossil record, and could be
> >arbitrary distinction in any case). However, I certainly agree with you
> >that using armor as a synapomorphy is definitely a bad idea. However, if
> >you could find synapomophies for a stegosaur plus ornithopod clade, I would
> >certainly consider them, but I strongly doubt that such a clade exists.
> > I am presently inclined to classify thyreophorans (sensu lato) as
> >paraphyletic (two separate, but adjacent clades) as follows:
> >ORDER ORNITHISCHIFORMES
> > 1 Pisanosauridae
> > 2 Lesothosauridae
> > 3 Plesion _Scutellosaurus_
> > B Aykylosauridae (incl. Scelidosaurus)
> > 4 Plesion Emausaurus
> > B Stegosauridae (incl. Huayangosaurus)
> > 5 Thescelosauridae
> > 6 Plesion Agilisaurus
> > 7 Plesion Echinodon
> > 8 Heterodontosauridae
> > ...and so on for other ceropodans....
> >Why does Stegosaurus HAVE to be an ornithischian? Just look at the
> >of life today. Stegosaurs, and other dinosaur groups for that matter, may
> >not be as closely related as is thought. We have hundreds of million's of
> >years of evolution and trying to classify them. And they all may not be as
> >closely related.
> >Tracy L. Ford
> Get your FREE download of MSN Explorer at http://explorer.msn.com
Hmmmm, sounds like a ready and waiting Master's Thesis if anyone is
up for it!