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RE: FW: Dracorex's phylogenetic position examined with science
Bob Sullivan wrote-
Mortimer has misrepresented my paper which primarily was
intended to be a taxonomic review (not a cladistic analysis) of
pachycephalosaurids based on my examination of the material. As far as
the phylogenetic analysis he proposes, I reject it on the grounds that
he has not personally studied the material and is apparently just
combing the literature for characters without properly assessing them.
As Tim pointed out, your paper did make phylogenetic claims, regardless of
its primary purpose. It and the Dracorex papers both had sections dedicated
to phylogenetic implications. I want to point out that I agree not every
paper needs a cladistic analysis. This was not my problem with Sullivan's
or Bakker et al.'s papers.
It's true I didn't examine any material firsthand. The characters were just
those of Williamson and Carr (2002) though. Like I said, the point was not
to test your ideas regarding Prenocephale or the sister group to
pachycephalosaurins vs. theirs. I didn't include your characters, so that
couldn't be tested. The point was that the homoplasic Dracorex is not the
problem for cladistics it was presented as, nor does its combination of
characters mean we should start questioning the standard results of
pachycephalosaur phylogenetic analyses. In fact, by putting Dracorex into a
previously made analysis, I tested this even better than if I had used my
knowledge of Dracorex when creating a novel matrix. Williamson and Carr's
matrix was 'unprepared' for Dracorex, in a way, yet it still handled the
taxon just fine.
The issue at hand, as I see it, is there is little compelling
evidence to produce a robust phylogenetic analysis vis-a-vis cladistic
analysis at this point in time as most of the material is too
incomplete. I find his comments regarding my work extremely offensive.
His implied assertion that cladistic methodology is the only way to do
"science" (no matter how poor the data are) is absurd. I note the
approach that he advocates only produces a "cladogram du jour" nothing
more. This is cladistic zealotry, not science. It is clear that he is
not critically assessing the data. He selectively chooses to embrace
(some) previous interpretations that result in a nice (albeit
simplistic), neatly nested, hypothetical hierarchy. He fails to
understand, in the fog of his cladistic zealotry, that cladograms are
nothing more than phylogenetic hypotheses (subject to revision as more
data are incorporated), they are not necessarilary truth (science).
Where to begin... It's true people haven't utilized much data yet when it
comes to determining pachycephalosaur phylogeny. But this doesn't mean we
shouldn't try with what we have. Maybe the data really are too poor at the
moment, but at least a cladistic analysis gives us something tangible and
somewhat objective that can be tested against additional data. I don't view
the result of any cladistic analysis as 'the truth', since I am well aware
of how labile they are (depending on which taxa, characters, states, etc.
are included). They are merely the best hypotheses available, given
currently utilized data. And this is what science is. Science is not truth
(which we may never know).
fact is that there is real disagreement over the validity of the
Marginocephalia and the interpretation that Stenopelix is a
I haven't seen such disagreement in the literature.
Marginocephalia seems to only get stronger, especially with the discovery of
Yinlong. The latter ironically lacks a parietal shelf, suggesting you may
be right (albeit for the wrong reason) in claiming this was convergent in
derived ceratopsians and pachycephalosaurs. However, its mosaic of
pachycephalosaur and ceratopsian features makes this irrelevent.
As for Stenopelix, every recent analysis I've seen has placed it in the
Pachycephalosauria. I haven't seen any contradictory evidence (none was
given in your paper, certainly), and stand by my statements regarding the
flaws in your rationale for excluding it. But as I also said, with the
recent discovery of Yinlong, we should reexamine Stenopelix to determine if
its pachycephalosaur characters are also found in basal ceratopsians.
His failure to recognize that the genus
Sphaerotholus is a junior synonym of Prenocephale, and Ornatotholus is
not distinct from juvenile Stegoceras, is illustrative of the cladistic
typology that he embraces. I do not find this (his approach) to be
credible science. Wishing it does not make it so and I reject his
embracement of this antiquated notion that all "flat-headed
pachycephalosaurid taxa are inherently primitive. One can manipulate the
data to effect the resulting tree.
One can indeed manipulate the data to affect the outcome. But at least in
cladistics such manipulation is transparent and has an objective effect on
The Prenocephale/Sphaerotholus issue was specifically not tested by my
analysis, as I previously said. Moreover, it's a subjective decision to
synonymize them even in your (2003) phylogeny, as the American species are
in a clade sister to P. prenes. And it's especially contentious if you keep
Tyolocephale separate, as I previously said, since only some of your trees
place P. prenes closer to the American species than to Tylocephale.
I never claimed Ornatotholus was distinct from Stegoceras. I specifically
wrote both you and Williamson and Carr interpret it as a juvenile
Stegoceras, and that exclusion of it and the other juvenile OTU
(Wannanosaurus) did not affect the cladogram.
I also never claimed all flat-headed pachycephalosaurs were inherantly
primitive. The fact flat-headed Dracorex was resolved as a
pachycephalosaurin should have made that clear enough. My point was that
just because some flat-headed pachycephalosaurs (Dracorex) are derived from
dome-headed taxa, that does not mean all others (Homalocephale, Goyocephale)
are. I stand by my statements that your reasons for deriving the latter
from dome-headed taxa are flawed. It would be nice to hear you defend them.