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Re: Paronychodon teeth are NOT homalocephalid fangs - killing an internet rumor

Thanks. That's very interesting to know. I forgot to note that whereas Paronychodon are more abundant in Maastrichtian than Campanian localities, the common Maastrichtian pachycephalosaurines lack premaxillary teeth and have more lateral teeth due to their longer snouts, so have even less fangs per lateral teeth.

Mickey Mortimer

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
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. 196, 33-77.

Mickey Mortimer