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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:

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.