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RE: Platecarpus tympaniticus - how to analyze a nomen dubium



--- On Wed, 22/9/10, Michael Mortimer <mickey_mortimer111@msn.com> wrote:

> From: Michael Mortimer <mickey_mortimer111@msn.com>
> Subject: RE: Platecarpus tympaniticus - how to analyze a nomen dubium
> To: dinosaur@usc.edu
> Received: Wednesday, 22 September, 2010, 2:11 PM
> 
> Mike Keesey wrote-
> 
> > > Actually, I think the PhyloCode leaves enough
> wiggle-room for us to do
> > > what is obviously the right thing here: Article
> 11.7 is the relevant
> > > one, and it says "In the interest of consistency
> with the rank-based
> > [...]
> >
> > I stand corrected; I think I was thinking of an older
> draft which
> > didn't say "typified name". "Ceratopsia" and
> "Ceratopsomorpha" are not
> > typified names under any rank-based code, so we can,
> in theory, define
> > them without Ceratops montanus.
> 
> I considered that as well, but Article 11.7 covers not only
> typified names under a rank-based code, but also clades
> "derived from the stem of a such a name."  So since
> Ceratopsia and Ceratopsomorpha are still derived from the
> stem of a typified name under the ICZN (Ceratops), they must
> also include that name as an internal specifier.  


I'm not so sure.  These are murky waters.  Yes, it is obvious that Marsh didn't 
come up with the Ceratopsia in a vacuum.  But when Marsh created a group called 
Ceratopsia, both _Ceratops_ and _Triceratops_ were known to him.  So we can't 
really be certain if Marsh derived Ceratopsia directly from _Ceratops_.  Sure, 
he incorporated the stem 'Ceratops' into Ceratopsia; but he also incorporated 
the same stem into his new genus _Triceratops_.


Although the principle of typification applied then (as now) to family-group 
names (such as Ceratopsidae), this did not apply to Ceratopsia.  When Marsh 
came up with the name Ceratopsia, it's doubtful whether he even thought in 
terms of "derived from the stem of _Ceratops_."  This is ad hoc, and 
anachronistic.  Who knows what went on in Marsh's head when he came up with the 
name 'Ceratopsia'?


Ceratopsomorpha is tricky, because it w
clade.  So no internal specifiers were provided.


> This is a
> good thing in my opinion, since it gets rid of the
> artificial difference between how family-level clades and
> other clades are treated.


I see the advantages of this.  It would ensure, for example, that Ornithosuchia 
would always include _Ornithosuchus_ - which is not always included in 
phylogenetic definitions of Ornithosuchia.



Cheers

Tim