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Cooper's thesis, a critical review
Judy E. Cooper, 2004. Pachycephalosaur cranial morphology and species
definition. M.Sci. thesis, Univ. Alabama Huntsville, 62pp.
This is hands down the worst thesis* I've read, even beating Czerkas' book
in the categories of inadequate research, misunderstanding the current
consensus, and unscientific theories. Furthermore, it features blatant
misrepresentation of authors' ideas and inaccurate bibliographical format.
* Yes, it's a thesis, but there are no new taxa or diagnoses, so discussing
it seems ethically sound.
The first part of the thesis involves her theory of pachycephalosaur domes
and nodes being used to direct sound waves for echolocation, which I have no
opinion on as of yet. It's the second section which I'll be commenting on.
"Also in the literature is a tradition of thought that pachycephalosaur was
herbivore. Though the first pachycephalosaurid specimen found was a tooth
which the genus was named Troodon, "wounding tooth", many researchers
to subscribe to the theory of herbivory."
You might think Cooper reassigns Troodon to the Pachycephalosauridae
somewhere in her thesis, but in actuality she seems to think that's the
"As mentioned earlier, pachycephalosaurids are included in Ornithischia
of the hip and rib configuration. They are included in Marginocephalia
of occipital bony projections. However, unlike any other Ornithischian, all
pachycephalosaurids have an anteriorly rotated occiput. In this paper I have
shown that they also had a convergent otic system with synapsids. The
ornithischian hip girdle and presence of occipital nodes seems to be
as phylogenetic evidence by the markedly anteriorly rotated occiput and
specialized hearing system. It is reasonable as part of my conclusions to
suggest a need for reassessing the classification of pachycephalosaurids as
ornithischian. The marked characteristics of the group warrant its own
No, no they do not. Cooper holds an antiquated view of phenetic taxonomy,
whereby derived characters can exclude a taxon from its ancestral clade. She
goes into further detail about it later. The occipital orientation and otic
specializations mean nothing without either positing relations with another
taxon that has them, or finding the ornithischian condition is derived.
Cooper has done neither. Her suggestion has as much relevance as removing
bats from Mammalia due to their echolocation and highly specialized
"For the purposes of this examination, the term "pachycephalosaur" will
all dome-headed animals, which could encompass those named under Troodon and
Stegoceras among the therapods as well as those species grouped within the
So Stegoceras is a theropod now? Or a 'therapod', as Cooper always spells
When discussing the standard phylogenetic view...
"Pachycephalosaur is shown to have split from the ceratopsian line with an
appreciable phylogenetic distance between them. Psittacosaur, a
bipedal animal, is shown to be less derived and on the ceratopsian side of
clad. ... All the Marginocephalia are shown within the order Ornithischia,
bird-hipped dinosaurs, which are distinct from the therapod line."
Cooper's inability to use vernacular forms of taxa correctly and use of the
word 'clad' is appalling, but common throughout the thesis.
"Pachycephalosaur is a bipedal dinosaur who remains appear in the late
Cretaceous. Estimated body size varies from small to "rather large.""
But further down the page she mentions pachycephalosaur species are known
from the United Kingdom, which would be Yaverlandia, from the EARLY
Cretaceous. She sure did her homework regarding size estimates.
"Pachycephalosaur taxonomy has presented considerable challenge to
Once past the phylum of Dinosauria, troubles begin."
Sure, Dinosauria has been advocated as a class, but this is ridiculous.
"Yet the teeth, back to the very first find in 1856, have repeatedly placed
certain pachycephalosaurs within the therapods. The serrated structure and
pattern of many specimens points to a carnivore, which by convention is not
ornithopod. Indeed, the most recent reshuffling of taxonomy has resurrected
previously discarded Stegoceras genus and placed it within the therapods
Why does Cooper think pachycephalosaurs are usually placed in Ornithopoda?
And much like Czerkas thinking theropods were defined by their inability to
climb, Cooper thinks ornithopods/ornithischians are defined by their
herbivory. Sullivan did NOT place Stegoceras into Theropoda, and saying
Stegoceras was ressurected by him after being previously discarded is
completely wrong. I don't know how Cooper could have thought this if she
read the paper. The only times the word "theropod" is mentioned in Sullivan
"Gilmore (1924) reported on the first complete skull, and partial
postcranial skeleton of Stegoceras validum (UALVP-2), but believed, based on
tooth morphology, that Stegoceras validum is a junior synonym of the now
well-known theropod dinosaur Troodon formosus."
"In a subsequent and important paper, Sternberg (1945) established the
family Pachycephalosauridae, reviewed all previously named taxa, and
correctly recognized that Troodon is a theropod dinosaur."
"Russell (1948) reaffirmed Sternberg's assessment that Troodon is indeed a
And a reference to Majungatholus.
Then Cooper figures Sullivan's cladogram, which is basically-
"As shown in the figure, pachycephalosaurs are grouped under the order
Ornithopoda and family Ceratopsidae."
Ah, so part of her confusion is caused by her inability to read a cladogram.
"Stenopelix also features a distinct frontal suture thought to be a
On the next page, she correctly notes Stenopelix has "no skull in record".
Cooper then rambles on for some length about the state of taxonomy, speaking
of the forms and essences of Aristotle and Plato as if they had any modern
relevence to science. It's all quite archaic philosophy, but she concludes
species are immutable in the way elements are and that taxonomy should be
essentialist. The closest she gets to criticizing phylogenetic systematics
is an invalid argument why the biological species concept is circular and a
quote from Mayr that it allows 'incongruous' taxa such as Archosauria.
"Because of the vaguely Ornithischian hip structure, and because of the
existance of bony nodes on the posterior skull, pachycephalosaur has been
classified as an ornithischian and therefore an herbivore. In order to
this classification, it is necessary to ignore pachycephalosaur's anteriorly
rotated frontoparietal dome, despite the fact this dome is
defining characteristic. It is also necessary to ignore the obviously
carnivorous teeth for which the species was first named. This taxonomic
confusion has arisen because systematists continue to upend form and
Why Cooper thinks a taxon's etymology has any relevence to its
classification is lost on me. If pachycephalosaur pelvises were found first,
and they were named for their wide ilia, would that be their defining
characteristic? Should all animals named after Chinese localities be grouped
together because of that? Also note the 'occiput' has turned into the
'frontoparietal dome', two different surfaces of the skull.
"If we orient the logic correctly, we can clear the taxonomic confusion.
Pachycephalosaur is defined by its frontoparietal dome. Virtually every
diagnostic character in the taxonomy deals with the dome, the squamosal, or
squamosal nodes. No other Ornithischian has the dome. No other Ornithischian
a marked anterior rotation to the frontoparietal. Ornithischians are
not carnivorous. It follows from this that pachycephalosaur is not
Ornithischian. It must be removed from that family and given its own
classification lateral to Ornithischia, the order of Pachycephalosauria."
Well, someone's logic is certainly oriented incorrectly, and I don't think
it's Sullivan, Sereno, et al.
Also of note, the bibliography of pachycephalosaur papers at the end lists
papers by multiple authors as multiple single-authored papers. So
Sampson, S. D., Witmer, L. M., Forster, C. A., Krause, D. W., O'Connor, P.
Dodson, P. and Ravoavy, F. (1998). Predatory dinosaur remains from
Implications for the Cretaceous biogeography of Gondwana. Science, 280:
Sampson, S. D. (1998). Predatory dinosaur remains from Madagascar:
for the Cretaceous biogeography of Gondwana. Science, 280: 1048-1051.
Witmer, L. M. (1998). Predatory dinosaur remains from Madagascar:
for the Cretaceous biogeography of Gondwana. Science, 280: 1048-1051.
Which is all the more confusing since she says it was presented in the
format recommended by the Council of Biology Editors (Scientific Style and
Format: The CBE Manual for Authors, Editors and Publishers, 6th ed., 1994).
Yet the CBE website (http://www.monroecc.edu/depts/library/cbe.htm)
recommends the usual method for citing multi-author papers.
I have a pdf of this, if anyone wants to judge it for themselves.
Undergraduate, Earth and Space Sciences
University of Washington
The Theropod Database - http://students.washington.edu/eoraptor/Home.html