From: "franklin e. bliss" <frank@blissnet.com>
To: mickey_mortimer111@msn.com, dinosaur@usc.edu
Subject: Re: Paronychodon teeth are NOT homalocephalid fangs - killing an
internet rumor
Date: Fri, 27 Jul 2007 19:50:39 -0600
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
MS Biostratigraphy
Weston, Wyoming
www.wyomingdinosaurs.com
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.
http://dml.cmnh.org/1997Dec/msg00058.html
Baszio, 1997. Investigations on Canadian dinosaurs: systematic
palaeontology of isolated dinosaur teeth from the Latest Cretaceous of
south Alberta, Canada. Courier Forschungsinstitut Senckenberg. 196,
33-77.
Mickey Mortimer
http://home.myuw.net/eoraptor/Home.html