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RE: Stegosaur volume of Swiss Journal of Geosciences
On Sat, 18/9/10, Anthony Docimo <email@example.com> wrote:
> > But how do we know that Ceratopsidae encompasses _Ceratops_?
> just a hunch....because that's how it was created in the first place?
Well, you'd be forgiven for thinking that. But many things have changed since
Marsh (1888) first came up with the family Ceratopsidae. We now use
phylogenetic taxonomy, which has unsettled certain time-honored assumptions.
Currently, every phylogenetic definition that has been proposed for
Ceratopsidae has pointedly excluded _Ceratops_, the name-giving taxon.
Instead, these definitions have included well-known genera such as
_Triceratops_ and _Centrosaurus_ (Dodson et al., 2004; Sereno, 2005), or
_Triceratops_ and _Pachyrhinosaurus_ (Sereno, 1998).
So if Ceratopsidae is defined as the least inclusive clade that includes
_Triceratops_ and _Centrosaurus_ (Sereno, 2005), then in order for _Ceratops_
to be a ceratopsid, it has to be shown to be a member of this clade. This can
only be done by phylogenetic analysis. Until this is demonstrated, it remains
an open question whether _Ceratops_ is a ceratopsid.
> then shouldn't our default assumption (at least until proven otherwise)
> be that _Ceratopsidae_ counts _Ceratops_ as a member?
No; we shouldn't be *assuming* anything. We should be hypothesizing, then
testing. The hypothesis is that _Ceratops_ is a member of the least inclusive
clade (Ceratopsidae) that includes _Triceratops_ and _Centrosaurus_. Until
this hypothesis is tested, it should not be simply assumed that _Ceratops_ is a
Both the ICZN Code and the draft PhyloCode actually require that _Ceratops_ (as
the name-giving genus) is a member of Ceratopsidae. Thus, we should either
include _Ceratops_ in the definition of Ceratopsidae; or we should scrap the
name Ceratopsidae for this clade.