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RE: Ceratops (was RE: Glishades ericksoni, ...)



Tim Williams wrote-

> But... we'll never know where _Ceratops_ sits in ceratopsian phylogeny. 
> _Ceratops_ is *never* included in a phylogenetic analysis, because it is a 
> nomen dubium.
>
> I'm not saying _Ceratops_ *should* be included in a phylogenetic analysis; 
> I'm only saying it *can't* be. This simple fact makes it impossible to 
> determine the content of Ceratopsidae if _Ceratops_ is a specifier. For 
> example, what if _Avaceratops_ comes out as a sister taxon to the 
> Chasmosaurinae+Centrosaurinae clade. Is _Avaceratops_ a ceratopsid? We could 
> only know this if _Ceratops_ is also included the analysis. But it isn't...

Er... there's nothing stopping someone from including nomina dubia in 
phylogenetic analyses.  It will just make a polytomy in the range of all the 
taxa it cannot be distinguished from.  And if that polytomy is within the 
Chasmosaurinae+Centrosaurinae clade, then using Ceratopsidae for that clade is 
just fine.

> IMHO, the best solution is to abandon Ceratopsidae altogether. We've 
> abandoned other family-level names that have been deemed to be based on 
> dubious genera (Deinodontidae, Trachodontidae, Titanosauridae, etc), so why 
> not abandon Ceratopsidae too? Having a definition of Ceratopsidae that 
> includes _Ceratops_, for the sole purpose of maintaining the name 
> Ceratopsidae, strikes me as special pleading.

My preference would be to only abandon names if the eponymous taxon isn't 
necessarily located within that clade.  "Dubious" is just too subjective a 
notion.  Of course this requires actual hard work and exhaustive comparison 
instead of just saying "Taxon X is only based on one bone whose original 
diagnosis is no longer valid- it's undiagnostic."  Has anyone actually tried to 
compare Ceratops to other related taxa?  I know they haven't for Deinodon, for 
instance.
 
Mickey Mortimer                                           
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