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Ceratops (was RE: Pterosaur diversity (was: Re: Waimanu))
Mickey Mortimer wrote:
Zuniceratops and Ryan's (still undescribed?) basal centrosaurine show this
isn't so. Large brow horns are plesiomorphic for ceratopsomorphs.
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. This contradicts Sereno (2005),
"Although the nominotypical genus and species, _Ceratops montanus_, is
generally regarded as a nomen dubium (e.g. Dodson et al. 2004), it is based
on two sizable horn cores and an occipital condyle from near the top of the
Cretaceous section in Montana (USNM 2411, Marsh 1888, Hatcher et al.
1907:figs. 103-104). The horn cores, although probably not from a fully
grown individual, are large enough to place securely within Ceratopsinae
(Chasmosaurinae) rather than Centrosaurinae."
According to PhyloCode (Recommendation 11.8B): ?If it questionable whether
the type specimen of a preexisting name belongs to a clade to be named
(e.g., because of the fragmentary nature of the specimen), then that
preexisting name (or its type) should not be used as a specifier? and the
corresponding name should not be converted to a clade name.?
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.
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).
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.