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tyrannosaur tooth diversity
Commenting on George's mini-monograph about tyrannosaurid systematics,
many years ago I did a big project on the functional morphology of
theropod teeth, ultimately published in 1991 in _Modern Geology_. I
was particularly interested in tyrannosaurid teeth from what is now
called the Dinosaur Park Formation. I looked at _in situ_ teeth in
the jaws of what was then called _Albertosaurus libratus_, but seems
now to be headed back to _Gorgosaurus libratus_, and also at _in situ_
teeth of _Daspletosaurus torosus_. I noticed some dental features
that were consistently different in the two forms:
1) Shape of the anterior serration keel: As you follow the anterior
keel from the tip of the tooth toward its base, in _Gorgosaurus_ the
keel curves sharply medially, toward the inside corner of the tooth.
In _Daspletosaurus_ the medial bending isn't anywhere near as
2) "Crinkles" along the posterior serration keel: In
_Daspletosaurus_ teeth, but not _Gorgosaurus_ teeth, there are little
crescent-moon shaped crinkles that run a short distance from the
posterior serration keel onto the side of the tooth.
In all the jaws of _G_ and _D_ that I was able to examine, and that
had been assigned to genus on the basis of non-dental criteria, the
difference between the two tooth morphs held up. I haven't worked on
theropod teeth in a decade now, so I don't know if they still hold up,
but I mention them for whatever they may be worth.
Now, this has no bearing on the question of whether _G_ and _D_ belong
to the same genus or different genera, but it does suggest that they
really are distinct at the species level.