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Re: Adios, "Brachiosaurus" brancai

2009/9/11 Tim Williams <tijawi@yahoo.com>:
> However, I certainly don't agree that all genera should be monospecific. 
>  Using that logic, _Psittacosaurus_ would have to be split up into six or 
> seven (or whatever) genera, which does not seem justified.

Well, I don't know anywhere near enough about ceratopsians to comment
intelligently on that particular case.  But are we really confident
that the complex of, what is it now, eight or nine Psitracosaurus
species is monophyletic with respect to the various other basal
ceratopsians that have been placed in other genera?  Because if not,
we're heading for a Great Renaming, and those are never fun.  Whereas
had those species all been placed in different genera in the first
place, then their names would be unaffected by phylogenetic
reshuffling.  That seems to me to be obviously A Good Thing.

(One multiple-species dinosaur I DO know about is Cetiosaurus, which
had thirteen(!) species before it was revised by Upchurch and Martin
(2003).  They reduced it to ONE valid species, C. oxoniensis, with the
others being nomen nuda, nomen dubia, or members of distantly related
sauropod groups.  I'm sure the situation with Psittacosaurus is
nowhere near so dire, as Cetio had to carry an awful lot of
19th-Century taxonomic baggage, but it's a cautionary tale

To be honest, if I had my way, I would do away with species
completely, promoting each species to a genus.  (Or, equivalently, do
away with genera, and promote species to uninomials, but that would
raise more practical problems as species names are not globally
unique.)  We simply don't need two ranks both defined as "this type
specimen and everything that is kinda close to it, more or less, if
you know what I mean".

>> If you want, you can put Giraffatitan and Sauroposeidon --
>> and
>> Cedarosaurus and Venenosaurus -- all into
>> Brachiosaurus.  And you can
>> put Opisthocoelicaudia into Saltasaurus, and Nemegtosaurus
>> into
>> Rapetosaurus; and then you can put Rapetosaurus into
>> Saltasaurus too,
>> since they are now  sister taxa, and so on back down
>> the tree till we
>> put Brachiosaurus (i.e. what we now call Brachiosauridae)
>> into
>> Saltasaurus, too.
> The phylogeny featured in Taylor (2009) (Figure 6) only includes two 
> traditional brachiosaurid OTU's: _altithorax_ and _brancai_.  This isn't a 
> comp
>  relationship would still be recovered for _altithorax_+_brancai_ if a larger 
> sample of taxa were included in the analysis, including those genera 
> mentioned by Mike (_Sauroposeidon_, _Cedarosaurus_, _Venenosaurus_).

Like I said in the SV-POW! post, others are working on the more
general problem of basal titanosauriform phylogeny.