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RE: Ceratopsine phylogeny questions



 <4AC9D5DD.7030905@gmx.at>
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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 at all=2C would thi=
s
>> affect the nomenclature?
>=20
> 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*.                                       =0A=
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