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RE: Ceratopsine phylogeny questions



As I understand it Michael, there is an excavation going on in Wyoming that is 
supposed to have a relatively complete _Nanotyrannus_ specimen. Really looking 
forward to any information they can divine from it--should clear up quite a few 
questions!

--- On Mon, 10/5/09, Michael Erickson <tehdinomahn@live.com> wrote:

> From: Michael Erickson <tehdinomahn@live.com>
> Subject: RE: Ceratopsine phylogeny questions
> To: dinosaur@usc.edu
> Date: Monday, October 5, 2009, 11:29 AM
> 
>  <4AC9D5DD.7030905@gmx.at>
> Content-Type: text/plain; charset="Windows-1252"
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> 
> 
> I definitely do NOT buy that *Nanotyrannus* is a juvenile
> *T. rex*=2C nor d=
> o I buy that *Dracorex* and *Stygimoloch* are ontogenetic
> stages of *Pachyc=
> ephalosaurus*. No way.
> =20
> But this thing about Torosaurus being the adult of
> Triceratops actually IS =
> pretty convincing=2C IMHO. Can't wait to see more about
> it!
> =20
> 
> > Date: Mon=2C 5 Oct 2009 13:17:49 +0200
> > From: david.marjanovic@gmx.at
> > To: dinosaur@usc.edu
> > Subject: Re: Ceratopsine phylogeny questions
> >=20
> >> While browsing the SVP meeting abstracts
> yesterday=2C This was=2C IMHO=
> =2C
> >> one of the more interesting ones:
> >=20
> > Quite so!!!
> >=20
> > Scannella briefly compared that situation to the
> synonymy of=20
> > *Nanotyrannus* and *Tyrannosaurus*=2C and
> *Dracorex*=2C *Stygimoloch* and=
> =20
> > *Pachycephalosaurus*.
> >=20
> > The obvious question -- whether Scannella had looked
> at postcranial=20
> > histology=2C too -- was immediately asked=2C and
> immediately answered by =
> "as=20
> > soon as I get back to the US"=2C which means he
> started last week. :-)
> >=20
> >> As the abstract notes=2C _Triceratops_ was named
> before _Torosaurus_=2C
> >> so it would seem _Torosaurus_ would be sunk into
> _Triceratops_.
> >=20
> > Correct.
> >=20
> >> However=2C since the type specimen of
> _Triceratops_ does not exhibit
> >> the adult frill morphology of the genus=2C how=2C
> if a

> > Not at all. As long as the type specimen can be shown
> to the new &=20
> > improved *Triceratops*=2C there's no problem.
> >=20
> >> In addition=2C it would seem possible that
> _Arrhinoceratops_ from the
> >> older Horseshoe Canyon Fm. might represent the
> adult morph (and
> >> senior synonym) of the recently named
> _Eotriceratops_. If the latter
> >> turns out to be the case=2C are there any real
> diagnostic differences
> >> between the adult morph of _Triceratops_ and
> _Arrhinoceratops_ that
> >> would justify separating these taxa at the generic
> level?
> >=20
> > What do you mean by "generic level"? There is no such
> thing as a=20
> > "generic level". .-)
> >=20
> > As long as they can be reliably told apart=2C which
> appears to be the cas=
> e=20
> > (correct me if I'm wrong)=2C they should be considered
> different species=
> =3B=20
> > whether you want to consider them different genera in
> addition is=20
> > entirely left to your (yes=2C your) taste.
> >=20
> >> To potentially muddy the waters further=2C where
> does this place the
> >> taxonomic status of _Torosaurus utahensis_?
> >=20
> > Good question. Wasn't mentioned in the talk or the
> question session. I=20
> > guess it could be a near-adult ontogenetic stage or a
> separate southern=20
> > species of *Triceratops*.    
>         
>           
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