Re: Torosaurus NOT Triceratops

[Paul P <turtlecroc@yahoo.com>]

--- On Thu, 3/1/12, David Marjanovic <david.marjanovic@gmx.at> wrote:

> > Am I the only one who thinks that the dataset used for the determination
> > of Torosaurus as a valid genus, or something synonymous with
> > Triceratops, is capable of being used to support either view...
> 
> Yes. It's not who analyses the data, but whether enough
> methods are used.

Um, actually, no. The data in this paper can be used to 
argue that they're separate taxa OR to argue that Toro. is 
Triceratops, just like you can pretty much show anything 
you want using many published character matrices. All you 
have to do is miscode one or two key characters for one 
or two key specimens. Note the asterisks in Longrich and 
Field's table. Statistically, i think that table/data 
shows that Torosaurus *is* Triceratops just as much as 
it shows the opposite. The more immature specimens are 
skewed toward Triceratops while the most mature are skewed 
toward Toro. I know that doesn't prove anything, but it's 
statistical. 

My hunch is that Torosaurus is valid, at least *some* 
Toros. In the end they may all prove to be synonymous, 
but what about those Toros in UT? Just a sampling issue? 
And what about immature chars in some Toro skulls? John 
Scannella and the MOR group have tried to address that 
using histology, but the dataset is still incomplete. 
As Denver says (i think), it's unfortunate that many of 
the older but well preserved skulls don't have detailed 
stratigraphic data with them, but they are still useful. 
They're not just heads floating in space or whatever. 

All dinosaurs are morphotaxa (er, all *extinct* dinos), 
so sample size is crucial. There is a lot of circularity 
in trying to separate individual variation from ontogeny 
from taxonomy from dimorphism in similar taxa. You can 
apply the tools, but in the end, it's largely statistical. 
I think in a year or two you will see someone arguing 
that Toro is the mature form only of *male* Trikes. 
Despite Horner and Padian on dimorphism, that seems to 
me a more likely 
-- On Wed, 2/29/12, Michael OSullivan <Michael.OSullivan@port.ac.uk> wrote:

> From: Michael OSullivan <Michael.OSullivan@port.ac.uk>
> Subject: Re: Torosaurus NOT Triceratops
> To: bcreisler@gmail.com, dinosaur@usc.edu
> Date: Wednesday, February 29, 2012, 6:45 PM
>
> Am I the only one who thinks that the dataset used for the determination
> of Torosaurus as a valid genus, or something synonymous with
> Triceratops, is capable of being used to support either view, depending
> on who's analysing the data. I think there's a real danger of
> subjectivity obscuring the reality. Whatever the hell that is...this
> rate, Torosaurus will be revealed to be a late living Stegosaur
> ---
> 
> Michael O'Sullivan
> 
> Palaeobiology Research Group
> Postgraduate Student
> School of Earth & Environmental Sciences
> Burnaby Building
> Burnaby Road
> Portsmouth
> PO1 3QL
> 
> Email:michael.osullivan@port.ac.uk
> >>> Ben Creisler  01/03/12 12:10 AM
> >>>
> From: Ben Creisler
> bcreisler@gmail.com
> 
> 
> A new paper in PLoS ONE:
> 
> 
> Longrich,  N.R. & Field, D.J. (2012)
> Torosaurus Is Not Triceratops: Ontogeny in Chasmosaurine
> Ceratopsids as a Case Study in Dinosaur Taxonomy.
> PLoS ONE 7(2): e32623.
> doi:10.1371/journal.pone.0032623
> http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0032623
>