Gross tooth morphology and serration morphology were examined to determine a quantifiable method for classifying tyrannosaurid tooth crowns from western North America. From the examination of teeth in jaws, tyrannosaurid teeth could be qualitatively assigned to one of five types based on the cross-sectional shape of the base of the tooth and characteristics of the mesial carina. A principal component analysis (PCA) revealed that much of the variance in tooth shape was a result of isometry, but some gross morphological variables exhibited strong positive allometry. Non-size associated factors were also important in determining tooth shape, particularly when data on denticle dimensions were considered in the analysis. While PCA identified important factors in variation, PCA ordination plots did not cluster the teeth into distinct, separate groupings based on taxon or bone of origin. The group classification functions determined by discriminant analysis, though not universally successful for classifying unidentified isolated teeth of all tyrannosaurids, do identify bone of origin of adult Albertosaurus, Daspletosaurus, and Gorgosaurus teeth at a statistically acceptable level.

Key words: Theropoda, Tyrannosauridae, dentition, classification, quantitative analysis, Cretaceous, North America.

Tanya Samman [tsamman@ucalgary.ca] and Leonard.V. Hills [lxxxvhills@ucalgary.ca], Department of Geology & Geophysics, University of Calgary, AB, T2N 1N4 Canada; G. Lawrence Powell [lpowell@ucalgary.ca], Department of Biological Sciences, University of Calgary, AB, T2N 1N4 Canada; Philip J. Currie [Philip.Currie@gov.ab.ca], Royal Tyrrell Museum of Palaeontology, P.O. Box 7500, Drumheller, AB, T0J 0Y0 Canada; present address: [philip.currie@ualberta.ca] Department of Biological Sciences University of Alberta Edmonton, Alberta, T6G 2E9 Canada.