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RE: Adios, "Brachiosaurus" brancai

John -- I agree with the first part of your message, but I'd quibble with the 
second part.  I don't think erecting a new genus for every new species (and 
therefore effectively treating binomials as de facto uninomials) is a 
particularly helpful idea.  Instead, each case should be assessed 
independently; and on that basis _Brachiosaurus_ and _Giraffatitan_ are 
probably best treated as separate genera, and (accordingly) as separate OTUs...

Although separating two sister taxa at generic level requires a certain level 
of hand-waving, I think Mike presents a strong case for separating _altithorax_ 
and _brancai_ into different genera.  If the name _Giraffatitan_ was not 
already available, then I think Mike would have been justified in erecting a 
new genus for _brancai_. 

As Mike says in his paper, _altithorax_ and _brancai_ are separated 
by at least 26 osteological characters.  Further, these differences have 
implications for overall body proportions.  

There's also the geographical separation between the two, then as now.  I know 
there's no reason why a genus couldn't contain widely geographically separated 
species during the Late Jurassic.  But I think you need compelling evidence for 
including a species from the Morrison and a species from the Tendaguru in a 
single genus.  

Finally, lumping _altithorax_ and _brancai_ into a single genus has led to 
these two species being treated as as a single _Brachiosaurus_ OTU in 
phylogenetic analyses.  This could be doing a disservice to titanosauriform 
phylogeny.  Sure, the analysis in Taylor (2009) recovered both as sister taxa; 
but this analysis included only two traditional brachiosaur taxa: _altithorax_ 
and _brancai_.  So the fact that _altithorax_ and _brancai_ were recovered as 
each other's closest relatives might be expected.  A wider sampling of basal 
titanosauriforms (including many "brachiosaurs" of traditional usage) might 
very well split up this _altithorax_+_brancai_ clade.  But even if it doesn't, 
I think there is enough qualitative evidence to split the two species up.

Given how incompletely known _altithorax_ is, much of what we think we know 
about _Brachiosaurus_ in North America has hitherto been based on the much 
better known _brancai_.  But the two are very different beasties.  Generic 
separation into _Brachiosaurus_ and _Giraffatitan_ helps reinforce this.



--- On Mon, 9/14/09, John Scanlon <riversleigh@outbackatisa.com.au> wrote:

> From: John Scanlon <riversleigh@outbackatisa.com.au>
> Subject: RE: Adios, "Brachiosaurus" brancai
> To: "'Mike Taylor'" <mike@indexdata.com>
> Cc: "'Dinosaur Mailing List'" <dinosaur@usc.edu>
> Date: Monday, September 14, 2009, 8:33 PM
> Mike Taylor wrote:
> > I thought we all agreed that uninomials are better
> than binomials because
> it's dumb to encode your phylogenetic hypothesis as part of
> the name.
> That was meant to be a joke, right? I think you are
> unlikely to get such
> agreement from anyone who works on extant organisms, fossil
> members of
> extant groups (e.g. mammals, birds, squamates,
> crocodylians, turtles) or
> comparatively well-sampled extinct groups like ceratopsians
> (would you erect
> a new genus for every species of Psittacosaurus?). 
> Why NOT encode a phylogenetic hypothesis as part of the
> name, if the
> hypothesis is supported at all and the binomial system
> allows it? In
> particular, if the name and the phylogeny coincide by happy
> coincidence, why
> mess with it? If your analysis does not refute a sister
> relationship between
> B. altithorax and B. brancai (it doesn't), nothing but
> clutter is gained by
> separating the genera. If Giraffatitan did not already
> exist, it would have
> been useless (in the context of your analysis) to invent
> it. In my opinion.
> -----------------------------------------------
> Dr John D. Scanlon, FCD
> Riversleigh Fossil Centre, Outback at Isa
> riversleigh@outbackatisa.com.au
> http://tinyurl.com/f2rby
> "Get this $%#@* python off me!", said Tom laocoonically.
> -----Original Message-----
> From: Mike Taylor [mailto:mike@indexdata.com]
> Sent: 11 September, 2009 7:59 AM
> To: qi_leong@hotmail.com
> Cc: Dinosaur Mailing List
> Subject: Re: Adios, "Brachiosaurus" brancai
> At the start of this thread, I wrote:
> > (And now we get into another discussion about what a
> "genus" is ...)
> And lo!  It was so!
> 2009/9/10 Jaime Headden <qi_leong@hotmail.com>:
> > On a purely technical level, I do think it is hasty to
> dismiss the
> identity of *"Brachiosaurus" brancai* as a species of
> *Brachiosaurus*, for a
> few reasons:
> Hasty?  Read the 20 meaty pages and then tell me it's
> hasty!
> >  Complexing the genera by recognition of
> *Giraffatitan* (which workers are
> still permitted to ignore) is not substantiated by a study
> that forces
> *brancai* closer to any other taxon other than
> *Brachiosaurus altithorax*,
> and from what I understand (unless Mike is willing to email
> me a copy of the
> paper) based on the SV-POW! post, the study receives a
> polytomy of
> "brachiosaurs."
> The PDF is prominently linked, twice, from the SV-POW!
> post.  Here's
> that link again:
> http://www.miketaylor.org.uk/dino/pubs/taylor2009/Taylor2009-brachiosaurus-a
> nd-giraffatitan.pdf
> The phylogenetic analysis follows that of Harris (2006)
> except in
> splitting the compound "Brachiosaurus" OTU into separate
> OTUs for
> Brachiosaurus proper and Giraffatitan.  In all MPTs,
> Brachiosaurus and
> Giraffatitan form a clade; but only one further step is
> required to
> make Giraffatitan a somphospondylian.
> > The questiuon here is: How is this information better
> conveyed by placing
> a species into a genus, versus placing all the species into
> a single genus?
> What does *Brachiosaurus* mean if it will only ever be
> synonymous with
> *altithorax*? The utility of nesting taxonomy is that
> containers can hold
> more than one internal "object" or name, and it seems a
> waste to support
> this for some tax and not others (especially since I
> suspect there is a
> drive to have genera -- a "species" is just not sexy enough
> to care about,
> and this issue plagues the *altithorax* problem).
> Genera are better than species because they are
> uninomials.  (Well: a
> name like "Xenoposeidon proneneukos" is a binomial by
> convention, but
> the reality is that its a uninomial that happens to have a
> space in
> the middle.)  I thought we all agreed that uninomials
> are better than
> binomials because it's dumb to encode your phylogenetic
> hypothesis as
> part of the name.  I guess you'd be happy with the
> generic name
> Giraffatitan if my phylogenetic analysis had recovered it
> as a
> somphospondylian; but then what do you do when Jeff
> Wilson's analysis
> comes along and recovers it closer to Brachiosaurus after
> all --
> rename it back to B. brancai?  And if it is recovered
> as the sister
> taxon to Euhelopus zdanskyi, are we going to rename it
> Euhelopus
> brancai?  Let's just not go there.  Monospecific
> genera, please!  Keep
> phylogeny and nomenclature separate.
> >  So my question is this: Why do we need
> *Giraffatitan*, and cannot have a
> *Brachiosaurus proteles* etc.?
> 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.  While you're at it, put Barosaurus
> into Diplodocus.
>  And so on until you consider Homo synonymous with
> Brachiosaurus.
> (Hey, I wouldn't mind being Brachiosaurus sapiens!) 
> If you want to
> avoid this degenerate conclusion, you have to draw a line
> somewhere.
> I am drawing it between Brachiosaurus and Giraffatitan.