TOOTH TYPE AND POSITION IN A HYPOTHETICAL PECTINODON BAKKERI JAW.

In 1856, Leidy first identified Troodontidae as a taxonomic unit. It was not until 1945 that C.M. Sternberg assigned it to a family status. There has been much debate on taxonomic naming in this family, but in 1987, Currie conflated all previous names into a single species, Troodon formosus. On the basis of isolated teeth, Carpenter (1982) suggested a second species, Pectinodon bakkeri from the Lance Formations. With limited specimens (24), Longrich (2008) proposed tooth positioning for the 4 tooth types he defined. This was especially challenging since no cranial or post-cranial skeletal structures have yet been identified.

Over the past 10 years, more than 500 P. bakkeri teeth have been collected from the Neufeld microsite on the Hanson ranch in northeast Wyoming. Initial collection of teeth from a western harvester ant nest, led to test sampling 12 plots on a grid spaced 8 meters apart. Additional sampling of the most productive area produced over 2000 defined elements including P. bakkeri teeth.

By measuring physical features such as crown height, basal width, basal length, posterior denticles per mm., anterior denticles, and wear marks, we have identified three major clusters of tooth shapes. Based on these results, we propose a modified positioning for teeth in P. bakkeri for yet undiscovered jaws.