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RE: Abydosaurus mcintoshi, a new sauropod from the Albian of Utah

Mike Taylor wrote:

<I'm not sure I understand what point Jaime is trying to make here, but I will 
say this. My paper noted 26 distinct osteological differences between 
Brachiosaurus and Giraffatitan, and showed that of the thirteen similarities 
proposed by Janensch, only four are valid synapomorphies of Brachiosauridae.>

  Mike is conflating a variety of arguments here.

  1. The sheer number of differences to defines a species and/or genus is to 
this point undefended. If applied to the natural world, one can get major 
upsets, and this is generally because it upsets standards of differentiation 
that are also ecological, or fly in the face of stability. These points have 
their own contenders who argue that their systems are the correct ones, and 
they are all arbitrary. This was pointed out to Mike in the previous 
incarnations of this can o' worms, and as I recall, Mike agreed it was 
_arbitrary_ to erect a taxon based on a NUMBER.  I made this point before, and 
Chure et al make it as well.

  2. Janensch's diagnosis is not the only foundation for a group of sauropods 
named Brachiosauridae, and to date, the definition, which presets the diagnosis 
to a complex of characters common to the components that fall into the 
container the definition provides, is based on *Brachiosaurus altithorax* (I 
previous wrote *altus*, which is indeed a travesty). While this is problematic, 
because the phylogenetics are based mostly on *B. brancai*, which is a point I 
had also previously agreed with Mike on, this can only bge overturned by 
further work on that mein. When Taylor (2009) produced a phylogeny separating 
the two taxa in context, they were found to be sister taxa. How then to defend 
the argument that they are not when the arguing work presents data otherwise as 
well? This is resolved through further work, not hand-waiving.

<Now I am not saying that means my conclusion is cast-iron or can't be 
challenged. But I do think it's enough evidence to have shifted the null 
hypothesis -- so that anyone who wants to challenge it really ought to make the 
effort to dig out some actual evidence themselves.>

  3. Taylor (2009)'s paper takes a portion to produce a the above phylogeny 
that does nothing to resolve the question of whether the taxa are congeneric, 
but instead uses the argument that only the NUMBER of differences can be used 
to differentiate the GENERA (not to mention _species_) as if the question of 
defined number of features relating to taxonomy had been settled. Surprise! It 

  4. The null hypothesis, to my understanding, is the situation you come to 
revise, rather than the product you revise into 9in this case). Specifically, 
taxonomy's null hypothesis is NOT naming new taxa. It is, rather, the 
conservative approach to lumping objects into containers BEFORE separating them 
out. So far, both *brancai* and *altithorax* can be put into two separate 
containers neither of the others can also fit into; these are supported by the 
taxonomic labels *brancai* and *altithorax*.

<What Chure et al. wrote -- "the identified differences have not been defended 
as separating genera, rather than species, populations, or individuals" -- 
really doesn't advance the discussion at all. It's an argument from laziness, 
and all it does is muddy the waters (and perpetuate the discredited notion that 
the Morrison and Tendaguru formations shared a fauna).>

  5. How, again, did supporting a differentiation of *Brachiosaurus brancai* 
from *B. altithorax* while supporting them as sister taxa advance the 
discussion? I can certainly agree with you that they are VERY distinct from one 
another, but without even knowing what Brachiosauridae consists of, whether 
using any given phylogenetic definition or by lumping a bunch of "similar" taxa 
in and seeing what happens, it is going to be very difficult to say that 
*brancai* is NOT a brachiosaurid. (I believe at one point you stated it was 
possible to support a
paraphyletic definition of a clade, although not specifically this one,
but if so, I can define the taxon to these two species, and then they
_would_ both be brachiosaurids by definition!)

  6. The notion of the Tendaguru-Morrison connection is irrelevant to this 
detail. Separating taxa based solely on disagreeing with this concept without 
producing any phylogenetic support (especially since Taylor, 2009, does the 
opposite!) is miore hand-waiving and more arbitrariness. It is more akin to 
naming new taxa just because they seem to derive from an overlying 
stratigraphic sequence. This thinking is making a problem in the issue of 
biostrat, and it rears its head here, too.

<On a more positive note: I am delighted that a sauropod has, at last, been 
named after John McIntosh. (Yes, there was Ultrasaurus/Ultrasauros macintoshi, 
but that is long dead.) The guy is an absolute legend: the comprehensiveness 
and insight of his publications would be way impressive if they were the work 
of a professional, but when you think that he did all that in his spare time 
while being a high-energy physics professor at Yale, it's just astonishing. 
No-one has ever more richly deserved to have a sauropod named after them.>

  Agreed! It is due time that Jack, whom I briefly met at SVP a few years back, 
gets a less controversial taxon named for his honor!


Jaime A. Headden

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