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Re: Ceratopsine phylogeny questions



How are you so convinced that the others are not ontogenetic stages,
yet think that this is? They use the same lines of reasoning, just
with different fossils.

On Mon, Oct 5, 2009 at 11:29 AM, Michael Erickson <tehdinomahn@live.com> wrote:
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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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