SAMMAN, T.*; POWELL, G.L.; CURRIE, P.J.; HILLS, L.V.; University of Calgary, Alberta; University of Calgary, Alberta; Royal Tyrrell Museum of Palaeontology, Drumheller, Alberta; University of Calgary, Alberta: Determining tooth position in the jaw of tyrannosaurid dinosaurs – biting off more than you can chew?

Differences in the size and shape of dinosaurian teeth can often be used to help identify the type of dinosaur to which they belonged. Characteristically, the crowns of tyrannosaurid teeth are nearly conical in shape and slightly laterally compressed, with round to ovoid cross-sections. The feasibility of quantifiably distinguishing alveolar position, bone of origin, ontogenetic stage, and taxon of origin for tyrannosaurid teeth is examined. Quantifiable distinctions would be extremely useful for the identification of isolated teeth. Isolated tyrannosaur teeth and teeth in jaws (including teeth from Albertosaurus, Daspletosaurus, Gorgosaurus, and Tyrannosaurus) were examined comparatively and morphometrically. A principal component analysis (PCA) revealed that much of the shape variance in the analyzed data set is associated with size (principal component I). An ordination of the PCA scores revealed substantial taxonomic overlap, with some minor separation of the large maxillary teeth of Tyrannosaurus rex. Ordination also revealed relatively little separation of bone of origin (i.e. premaxilla, maxilla, or dentary). Alveolar position is difficult to predict, possibly as a result of the pattern of tooth replacement. Discriminant analysis based upon isolated teeth showed that determination of bone of origin is possible in some cases. In general, however, it is very difficult to quantifiably separate the teeth of tyrannosaurids.