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RE: Ceratops (was RE: Pterosaur diversity (was: Re: Waimanu))
Tim Williams wrote-
So the size of the horn cores is useless for diagnosing
Chasmosaurinae/Ceratopsinae. Thus _Ceratops_ cannot be demonstrated to be
a "ceratopsine", and it cannot be demonstrated not to be a centrosaurine,
or a non-ceratopsid ceratopsoid for that matter. <snip>
Sereno does not use _Ceratops_ as a specifier, but _Ceratops_ is the
eponymous genus for Ceratopsoidea, Ceratopsidae, and Ceratopsinae. It
might be best to abandon these names, and replace Ceratopsidae with
Centrosauridae. Sereno suggested replacing Chasmosaurinae with
Ceratopsinae back in 1998, but the idea didn't exactly take off (as Sereno
 admits), so Ceratopsinae can just be brushed under the carpet, IMHO.
Well, not so fast. Horn core size isn't necessarily the only character
which can be evaluated for Ceratops. Perhaps other skull roof or occipital
characters can distinguish ceratopsids from more basal taxa, or
centrosaurines from chasmosaurines. In fact, Ryan's thesis finds that his
unpublished taxon is extremely similar with Ceratops and from equivalent
beds. I wouldn't be surprised if they were synonymous, though Ceratops'
holotype is not as obviously diagnostic.
Salgado (2003) also cites PhyloCode Recommendation 11.8B to support
upholding the use of the name Titanosauridae, because _Titanosaurus
indicus_ (usually regarded as a nomen dubium) is clearly a member of the
clade Titanosauridae, which is diagnosed by procoelous middle caudals.
However, there is no guarantee that this character might not turn up in a
more basal titanosaurian taxon (or even a non-titanosaurian sauropod - some
of which show procoelous proximal caudals).
True, but again we have other characters to consider (e.g. neural arch
placement). I don't think anyone doubts Titanosaurus is a titanosaurid (in
the sense of being more closely related to Saltasaurus than Andesaurus; not
a phylogenetic definition, but you get the clade I mean). I'd agree with
Salgado. There's nothing in the ICZN saying family names shouldn't be based
on nomina dubia.
My point (sorry I didn't get there sooner) is that it is bad policy to name
family-level clades after nomina dubia (or even fragmentary taxa).
_Ceratops_/Ceratopsinae/Ceratopsidae is a good test case.
To play devil's advocate, both Ceratops and Titanosaurus were very
distinctive when they were first found. It's only with hindsight that we
know strongly procoelous caudals and large brow horns have wide