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Re: Paronychodon teeth are NOT homalocephalid fangs - killing an internet rumor
Jaime A. Headden wrote-
I doubt this shows as much clear data as described, though somewhat
misleading in the extent that it would skew results toward a particular
when the tooth crowns recovered demonstrate a type recovery versus
Tooth type, rather than taxon type, tends to differ in that some taxa
similar types of teeth despite being wildly different. Historic confusion
predatory archosaur teeth throughout, say, the Jurassic and Triassic has
some amusing confusing uses of "teratosaurid" ("rauisuchian") teeth for
dinosaurs, among others. Finding what are conventionally a predatory
in some non-predaceous-seeming taxa, such as recurved, ziphodont teeth in
"prosauropods" and basal ornithischians, skews the assumption bias based on
isolated teeth. Applying these assumptions to mass collections without
extensive comparisons to morphological variation in even a single jaw
assuming as has been historically popular that "reptiles" are homodont
a single dental morphology]) causes such a biased skew towards types.
My anatomical and stratigraphic points stand regardless of how many taxa
have Paronychodon teeth. The frequency analysis might be compromised, as
some small percentage of Paronychodon teeth could hypothetically be
pachycephalosaur fangs, leading to a properly large ratio between cheek
teeth and fangs.
The assumption of homodonty was not made in my post.
*Goyocephale*'s dentary teeth are worn, from the apex basally down the
margins and onto the lingual as well as the labial surfaces, causing a pair
longitudinal wear surfaces and the formation of not one, but three lingual
"ridges", one of which lies between the two wear facets and is produced
distinctly as a result, and one "ridge" at each external boundary to these
facets. This is not a "normal" morphology of the tooth which would never be
found unworn or intact, due to diet. This is also not normal for a
One has but to look at tusked vegatarians to examine the functionality of
elongated "canine" teeth, though this begins to cause issues that arise
one makes comparisons between reptiles and mammals.
That only strengthens my argument, as the ridges of Paronychodon teeth are
not caused by wear. Rather, the apex and the base get worn first, then the
entire lingual surface is worn, sometimes eroding away the ridges. The
completely different wear facets are a powerful argument the teeth are not
homologous, as they were obviously interacting with other teeth differently.
*Stegoceras* is not a representative pachycephalosaur, but is abundant
DPP to some degree, this is largely due to its dome. Collections in the DPP
have produced numerous other taxa, some with intact jaws (e.g.,
*Sphaerotholus*), but with a strong bias towards domes. Some flat-headed
are known from overlying levels, such as *Dracorex* which presumably has
premaxillary teeth, and the undescribed "Sandy" specimen which may or may
be related or like *Pachycephalosaurus* (which also has premaxillary
However, these teeth differ in morphology from those of *Goyocephale*, and
*Homalocephale* is incomparable as it lacks this region of the jaws.
Additionally, no pachycephalosaur jaw has been recovered to date that
to *Goyocephale*, upper or lower, in development of the mesial dentary
dentition or the distal premaxillary dentition. It then seems curious why
possible to use this data of known pachycephalosaur material to rate
comparisons to one, argually "basal" taxon? The sampling bias also seems
curious if given in relation to the dietary functionality of
teeth, but also in the referal of both the collection to particular taxa or
particular taxa (junkbin taxa), and the arguably testy concept of making
general morphology referals to particular taxa, even particular species. A
valid criterion or two would be helpful when evaluating tooth-based taxa
one starts dismissing a referal, or supporting it, for that matter.
Stegoceras may not be representative (or it may be, how are we to know?),
but it is one of the few pachycephalosaurs known from anterior dentition
besides Goyocephale. It is also known from the same strata as Paronychodon,
so is good for comparison for that reason. Sphaerotholus has very poorly
preserved anterior dentary teeth, which nonetheless are different from
Paronychodon in having labial and lingual cingula, and a labial wear facet.
There is no mention of grooves, and though broken, the crowns appear to be
Dracorex actually lacks premaxillary teeth (Bakker et al., 2006), while no
Pachycephalosaurus premaxillae are known (though Brown and Schlaikjer
sggested it lacked premaxillary teeth due to anterior maxillary morphology).
As for why I would compare the frequency of pachycephalosaurid teeth with
Paronychodon teeth, when Goyocephale-like taxa are the concern, I was giving
Olshevsky the benefit of the doubt. The best case scenario if you will-
that some Late Cretaceous North American pachycephalosaur teeth may be from
Goyocephale-like taxa. As I previously mentioned, the fact Goyocephale-like
taxa are restricted stratigraphically is another argument against them
having Paronychodon teeth.
Obviously Baszio had criteria for assigning teeth to each taxon. The fact
he did that work means I don't have to, though obvously further confirmation
and examination is always valuable in science.
So far, body fossils of a number of curious dental taxa are unknown,
extensive sampling, which suggests that we do, in fact, have body fossils
these taxa, or that these are more on the line of predators in which
is left more frequently than body parts, or that the animals in question
not lowlands/watershed dwellers and don't normally arrive at the regions in
which their teeth arrive sedimentologically or geologically.
I agree that we have body fossils for these taxa, though they are currently
unrecognized. If Richardoestesia, Paronychodon and Zapsalis are
dromaeosaurids, as I believe, then some of the non-dental remains currently
assigned to Saurornitholestes, Dromaeosaurus or even Troodon may belong to
them instead. In addition, there are numerous unidentified small theropod
elements from the Dinosaur Park Formation which may belong to them.
Your second point is also true. Just look at how many coelurosaur bones are
known versus teeth from the Dinosaur Park Formation. Or how few published
North American avimimid or mononykine elements there are.
We don't know sh*t about tooth-based taxa.
We can be fairly certain that Paronychodon teeth are not cf. Goyocephale
fangs though. None of your points have made that possibility more likely,
and your wear discussion made it considerably less likely.