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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
hasn't.
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!
Cheers,
Jaime A. Headden
"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
"Human beings, who are almost unique in having the ability to learn from the
experience of others, are also remarkable for their apparent disinclination to
do so." --- Douglas Adams (Last Chance to See)
"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)
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