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RE: Mojoceratops ...



> > The type material of âEoceratops canadensisâ
> > and âChasmosaurus kaiseniâ are nondiagnostic and these
> > names are therefore considered nomina dubia, but their
> > morphology is consistent with Mojoceratops

> > The frill of Mojoceratops shows marked variation.
> > Some of this variation probably results from
> > intraspecific variation or ontogenetic changes

Those two statements raise a warning flag and should give
pause to anyone who is considering naming a new ceratopsid
taxon. If this is becoming a trend, it is disturbing.
It seems that the problem is with reviewers, at least
in part, for sanctioning the current naming spree. 
The holotype of C. kaiseni is an almost complete skull,
so claiming that it's nondiagnostic is to suggest that an
entire bonebed is needed to diagnose a species. That
simply is not the case.


--- On Wed, 7/7/10, Jaime Headden <qi_leong@hotmail.com> wrote:

> From: Jaime Headden <qi_leong@hotmail.com>
> Subject: RE: Mojoceratops and venomous Sinornithosaurus
> To: "Ville Sinkkonen" <villesink@gmail.com>, 
> Dinosaur.Mailing.List@listproc.usc.edu
> Date: Wednesday, July 7, 2010, 4:13 PM
>
>   Re: *Mojoceratops*: Ah, another taxon to add to my
> "probable synonyms turned into nomina dubia" list, although
> a funky name. And just so that it's clear, no, I've not read
> the paper; my comment above is intended to remark on the
> fact that a series of taxa have been erected only seeming
> after previous potential synonyms are rendered "nomen
> dubium" status, permitting not only a full genus, but a full
> species, status for a new specimen. It stresses the purpose
> of implying referral of a specimen which is name-bearing to
> a newly erected taxon with its own name-bearing type.
>
>   In context to longitudinal dental root-crown sulci (I've
> not read Gianechini et al,, but based only on the comments
> on the list), though:
>
>   While previously it has been suggested that the
> longitudinal sulcus on the labial surface of theropod teeth
> are a taphonomic artefact, it should be
e taxa
> possess a specific "bilobate" form of the root where the
> root and the basal part of the crown appear to have a
> rounded-hourglass (or bilobate) aspect in cross-section.
> This is not a typical preservational artefact, as it occurs
> in skulls and dentition with otherwise no other signs of
> distortion, and include specimens preserved outside of the
> typical bedding "crushing"plane. While it may still be
> taphonomic than actual, at least some taxa with extreme thin
> teeth (< 25% labiolingually wider than mesiodistally
> long) including *Allosaurus* and some dromaeosaurids and
> troodonts (not all of them) have this feature and it is
> seemingly omnipresent regardless of mode of preservation.
>
>   However, a preservational artefact does exist in which
> the sulcus is abnormally present, and this occurs when there
> is a distinct angular, and hairline, fracture associated
> with bending through gradual, persistent compression. These
> fractures will often have an irregular line when viewed in
> detail, but otherwise appear as though the sulcus is
> V-shaped. Extremes of this type of compression/bending (I am
> unsure of the process) may include split teeth, where a
> crown is longitudnally split in two, a mesial and a distal
> side.
>
>   You will find similar fractures in long bones compressed
> along their axis, deforming them from their normal shape.
>
> Cheers,
>
> Jaime A. Headden
> The Bite Stuff (site v2)
> http://qilong.wordpress.com/
>
> "Innocent, unbiased observation is a myth." --- P.B.
> Medawar (1969)
>
>
> "Ever since man first left his cave and met a stranger with
> a
> different language and a new way of looking at things, the
> human race
> has had a dream: to kill him, so we don't have to learn his
> language or
> his new way of looking at things." --- Zapp Brannigan
> (Beast With a Billion Backs)
>
>
>
>
> ----------------------------------------
> > Date: Wed, 7 Jul 2010 22:32:24 +0300
> > From: villesink@gmail.com
> > To: dinosaur@usc.edu
> > Subject: Mojoceratops and venomous S
> >
> > Nicholas R. Longrich. 2010 Mojoceratops perifania, A New Chasmosaurine
> > Ceratopsid from the Late Campanian of Western Canada. Journal of
> > Paleontology 84(4):681-694.
> >
> >
> > Abstract
> >
> > A new genus of long-horned chasmosaurine ceratopsid is described from
> > the Dinosaur Park Formation (upper Campanian) of Western Canada.
> > Mojoceratops perifania is represented by a skull and a parietal from
> > the Dinosaur Park Formation of Alberta and an isolated parietal from
> > the Dinosaur Park Formation of Saskatchewan. Several other specimens
> > are provisionally referred to this taxon. While Mojoceratops shares
> > many plesiomorphies with Chasmosaurus, the animal lacks the
> > forward-curving parietal epoccipitals and reduced postorbital horns
> > that diagnose the genus Chasmosaurus, and it differs from all other
> > chasmosaurines in exhibiting a prominent sulcus on the anterior margin
> > of the parietal, swellings on the anterodorsal surface of the parietal
> > rami, and a small accessory process on the first parietal epoccipital.
> > Other unusual features include anteriorly extended parietal fenestrae,
> > a broad, heart-shaped frill, and transverse expansion of the
> > postfrontal fontanelle. The type material of âEoceratops canadensisâ
> > and âChasmosaurus kaiseniâ are nondiagnostic and these names are
> > therefore considered nomina dubia, but their morphology is consistent
> > with Mojoceratops and they probably belong to this genus. The frill of
> > Mojoceratops shows marked variation. Some of this variation probably
> > results from intraspecific variation or ontogenetic changes, but
> > because the Dinosaur Park Formation encompasses more than a million
> > years of time, evolution may explain some of these differences.
> > Phylogenetic analysis shows that Mojoceratops forms a clade with
> > Agujaceratops mariscalensis; Chasmosaurus is the most basal member of
> > Chasmosaurinae.
> >
> > etc.........
> >
> > Cheers
> >
> > -Ville
>     
>         
>   
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