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RE: Australodocus a titanosauriform and other new papers




Whitlock's issue is the same one I had (here: 
http://qilong.wordpress.com/2011/03/11/systematic-originalism/) when dealing 
with Taylor resurrecting Paul's otherwise unused *Giraffatitan*: The use of 
*Giraffatitan* superimposes the idea or concept of "genus" on the discussion of 
diversity; that "brachiosaurids" are _more diverse_ than previously argued; 
that *altithorax* and *brancai* have a lot of differences, but that 
*altithorax* vs. *brancai* is "insufficient" to recognize this; and that no 
analysis published supports placing *brancai* anywhere else than next to 
*altithorax* -- and when highlighting this latter argument, Taylor failed to 
support it when splitting them and then testing them cladistically.

  The argument that we are better at facilitating communication by using a 
binomen, in this case a genus-species couplet (as used by Taylor when 
resurrecting the taxon name), fails because the objective value of the genus is 
inherently tied to a failed systematic system, the Linnaean System. Taylor's 
reply on my argument against this pattern was "What other system have we got?" 
What other, indeed. This is ridiculously silly because at the time Taylor 
supported this argument, he was also supportive of PhyloCode, which does not 
treat genera as valid objects. You either have a species, or a clade. And a 
clade containing only a species collapses to that species, meaning this object 
is redundant. And this is where we are going, right now: creating redundant 
clades containing only a single species for fossil taxa, as if it means we are 
recognizing new, special taxa. Many of the systematists who do this even 
recognize the idiocy of the genus-species couplet.

  There is only one validation I can see for this nomenclature, and that's if 
and when *brancai* arises apart from any monophyletic clade containing 
*altithorax* _consistently_, or if we just abandon the idea of nesting 
_species_ and just create binomina for all species taxa. This means we get 
*Brontosaurus* back, incidentally. But I doubt that the latter will happen any 
time time, and I doubt anyone will abandon the sexiness that is naming "genera" 
for all the notoriety and attention these "special names" bring to the field. 
And seriously, I suspect this is why a lot of otherwise "lumpable" taxa get 
named in the first place, despite the lack of a "difference" metric that seems 
presumed by a host of authors.

Cheers,

Jaime A. Headden
The Bite Stuff (site v2)
http://qilong.wordpress.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
Backs)


----------------------------------------
> Date: Tue, 12 Jul 2011 14:34:37 +1000
> From: tijawi@gmail.com
> To: dinosaur@usc.edu
> Subject: Re: Australodocus a titanosauriform and other new papers
>
> bh480@scn.org wrote:
>
> > John A. Whitlock (2011)
> > Re-evaluation of Australodocus bohetii, a putative diplodocoid sauropod
> > from the Tendaguru Formation of Tanzania, with comment on Late Jurassic
> > sauropod faunal diversity and palaeoecology.
> > Palaeogeography, Palaeoclimatology, Palaeoecology (advance online
> > publication)
> > doi:10.1016/j.palaeo.2011.07.001
> > http://www.sciencedirect.com/science/article/pii/S0031018211003579
>
>
> I'm not qualified to comment on the merits of the assignment of the
> cervicals named _Australodocus_ to basal Titanosauriformes... but two
> things come to mind:
>
>
> Firstly, if _Australodocus_ is *not* a diplodocoid, does that mean
> that all the diplodocid material from Tendaguru can be returned back
> to _Tornieria_?
>
>
> Secondly, I'm bewildered by Whitlock's reasoning for sinking
> _Giraffatitan_ into _Brachiosaurus_:
>
> Although numerous morphological differences exist between B.
> altithorax and B. brancai, the genus Brachiosaurus has never been
> demonstrated
> to be polyphyletic. Failing that, without a recognized criterion
> for determining
> whether two taxa are either distinct palaeospecies or palaeogenera based on
> morphology alone, the decision to replace an existing name (in this case,
> Brachiosaurus) with a different one (Giraffatitan) must be seen as somewhat
> arbitrary. Because low-level palaeotaxa are perhaps best seen as convenient
> shorthand for facilitating discussion and not as equivalents of
> neontological
> species or genera, it may be preferable to retain existing names whenever
> possible and thus maintain consistency with what is often decades
> of previous
> scholarship.
>
>
> Jee, I don't know about that. I'm not sure that fossil genera and
> species should be seen as "convenient shorthand for facilitating
> discussion". That seems excessively cynical to me - and lazy. But
> even if we follow Whitlock's advice (and I'm by no means suggesting
> that we should), keeping _Giraffaititan brancai_ in _Brachiosaurus_ is
> still a bad idea because it facilitates the *wrong* sort of discussion
> - such as overstating the commonalities in the dinofauna between the
> Morrison and Tendaguru. (Ironically, Whitlock's study actually
> emphasizes how different the Tendaguru environment was from the
> Morrison, and highlights the impact this had on relative sauropod
> diversity and browse regimes.)
>
>
> Further, to "maintain consistency with what is often decades of
> previous scholarship" raises alarm bells, because a large portion of
> this previous scholarship sometimes involved low standards for
> taxonomy. And by 'low', read 'crap'. Nearly a century ago, Tendaguru
> taxa were lumped into established Morrison genera unless there were
> compelling reasons not to (like _Kentrosaurus_). It was Janensch's
> default setting. Janensch's reasons for assigning the Tendaguru
> species _brancai_ to _Brachiosaurus_ were highly suspect, especially
> considering that he had never seen the North American _B. altithorax_
> material. As further noted by Taylor (2009), "Because this assessment
> did not describe specific derived characters shared between the
> Tendaguru forms and _Brachiosaurus altithorax_, it would not be
> considered a valid justification for the referral if published today."
> I aver we should be using current standards for dinosaur taxonomy,
> not those exercised at the beginning of the last century.
>
>
> To make the taxonomic issue more confusing, Whitlock's comparison of
> _Australodocus_ to _Brachiosaurus_ concludes:
>
> Whether these differences are sufficient to differentiate them at
> the generic level
> is uncertain. In a purely utilitarian sense, the argument is
> unnecessary - the names
> as known serve to distinguish between the taxa, regardless of the
> signifier used -
> and so _Australodocus_ is retained here.
>
> So for the sake of tradition and convenience, African _Giraffatitan_
> gets put back into North American _Brachiosaurus_ - but a second
> presumptive brachiosaur from Tendaguru (_Australodocus_) remains as a
> standalone genus...despite the stated opinion that it is "uncertain"
> whether the two Tendaguru titanosauriforms can be differentiated at
> the genus level?! I'm not warming to this purely utilitarian approach
> one bit.
>
>
>
>
>
> Cheers
>
> Tim