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RE: Australodocus a titanosauriform and other new papers



When we discussed this on your blog, we narrowed our disagreement down to the 
fact that you don't see genera as clades.  But I can assure you that Taylor, 
Williams, myself and most others on here DO think of genera as being clades.  
Thus retaining brancai in Brachiosaurus implies it is in a clade with 
altithorax to the exclusion of Sonorasaurus, Cedarosaurus and every other named 
genus.  And THAT's the reason we all have a problem with it.  You may view 
genera as just Linnaean labels, but most of us see them as implying monophyly.

Mickey Mortimer

----------------------------------------
> Date: Tue, 12 Jul 2011 00:05:04 -0600
> From: qi_leong@hotmail.com
> To: tijawi@gmail.com; dinosaur@usc.edu
> Subject: 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
>