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Re: Paronychodon teeth are NOT homalocephalid fangs - killing an internet rumor
At my Hell Creek localities, I have slightly more paronychodon teeth
than Pachychephalosaur teeth coming from the microsites. (Neither are
common.) I do find some obvious Pachycephalosaur material (a very
nice skull cap and several squamosal spines). I would expect many
more Pachycephalosaur teeth than I actually find here. While not very
large, their distinctive patterning makes them easy to spot.
Frank (Rooster) Bliss
On Jul 27, 2007, at 5:57 PM, Michael Mortimer wrote:
While researching Paronychodon for my website, I came across a
rumor started on the DML by Olshevsky, and decided I might as well
kill it on the DML as well.
An odd possibility was suggested by Olshevsky (DML, 1997), that
some Paronychodon specimens, including the holotype, may be
anterior dentary fangs of "homalocephalid" pachycephalosaurs (cf.
Goyocephale) . However, the dentary fangs of Goyocephale are
serrated distally, polygonal in section, have a bulbous root, and
seem to only possess one lingual ridge. Premaxillary teeth of
Goyocephale are somewhat similar to type B teeth of Paronychodon,
but lack ridges, are much less labiolingually compressed, and have
distal serrations apically. Stegoceras teeth are even less similar,
being serrated both mesially and distally with no ridges. The
supposed Middle Jurassic pachycephalosaur Ferganocephale has
vertical enamel ridges on the base of one side and lacks
serrations, but is otherwise highly distinct, being unrecurved,
short and uncompressed labiolingually, with a prominent cingulum.
The ridges radiate from the base instead of the apex and the entire
tooth shape is distinctively ornithischian. Besides the anatomical
differences, stratigraphically Paronychodon and "homalocephalids"
are also mismatched, with the latter only known from the Campanian-
Maastrichtian of Mongolia and perhaps China. The utter lack of
"homalocephalids" in well sampled strata like the Dinosaur Park
Formation is particularily telling. Also notable is that each
"homalocephalid" only had eight fang-like teeth, but had around
sixty-six leaf-shaped teeth. So we would expect more
pachycephalosaur teeth by a factor of 8:1 or so, but Baszio (1997)
showed this is not the case. For instance, he recorded 12
Paronychodon teeth from the Dinosaur Park Formation, and only 16
pachycephalosaur teeth. Similarly, Baszio recorded 84 Paronychodon
teeth from the Milk River Formation, but only 16 pachycephalosaur
teeth. Finally, Zinke and Rauhut (1994) described paronychodontid
teeth within a theropod dentary fragment, though these differ from
Paronychodon in some details.
References- Zinke and Rauhut, 1994. Small theropods (Dinosauria,
Saurischia) from the Upper Jurassic and Lower Cretaceous of the
Iberian Peninsula. Berliner geowiss. Abh.. E 13, 163-177.
Baszio, 1997. Investigations on Canadian dinosaurs: systematic
palaeontology of isolated dinosaur teeth from the Latest Cretaceous
of south Alberta, Canada. Courier Forschungsinstitut Senckenberg.