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RE: Platecarpus tympaniticus - how to analyze a nomen dubium
Rescued from the [SNIP] demon...
Mickey Mortimer wrote:
> 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
Ceratopsomorpha is tricky, because it was erected as an apomorphy-based 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.