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Re: Adios, "Brachiosaurus" brancai

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>From      : owner-DINOSAUR@usc.edu
To          : tijawi@yahoo.com
Cc          : dinosaur@usc.edu
Date      : Fri, 11 Sep 2009 01:20:34 +0100
Subject : 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? 

Maybe not....in my own ceratopsian phylogeny (which include all named 
psittacosaurian species plus all basal neoceratopsians), Psittacosaurus 
sinensis,P. sibiricus, P. lujiatunensis, and P. gobiensis come closer to 
Hongshanosaurus than 'true' Psittacosaurus. Although this group is not well 
supported, the main problem is that psittacosaur species are terribly 
homoplatic, and future discoveries or reappraisal of currently poorly known 
species (P. mazongshanensis, P.ordosensis, etc) could change the relationships 
Best regards

Lukas Panzarin

 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
> nonetheless.)
> 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.