Since dinosaur fossils are not numerous enough for statistics, the idea of studying dinosaurs at all has been questioned. Teeth of Judith River tyrannosaurs (late Cretaceous of south-central Alberta, Canada) are sufficiently numerous and rich in anatomical structures for statistical analysis: 1. No difference was found between widths of serrations of anterior and posterior rows (Mann-Whitney U test, two-tailed; n = 24 tooth fragments: p> .05; anterior and posterior x = 0.4 mm): 2. Reversals in uniform trends in serration width within each serration row were more numerous for the anterior (reversals = 51; non-reversals = 74) than for the posterior (reversals = 45; non-reversals = 135) serration rows (χ2 (2×2) = 7.82; d.f. = 1; p< .01); 3. Serrations of the anterior row are more steeply angled toward the point of the tooth than are those of the posterior row (Mann-Whitney U test, two-tailed, n = 21 tooth fragments; p< .01; anterior x̄ = 8.9°; posterior x̄ = 5.0°): 4. Small teeth (mean length = 9.8mm) show less tendency to be scratched than large ones (mean length = 25.0mm) (t(d.f. = 234) = 4.64; p< .01); 5. Inter-serrational slots of posterior row require less force (x̄ = 0.14 newton) to cut standard nylon filament (diameter = 0.04mm; tensile strength = 0.42 newton) than did slots of the anterior row (x̄ = 0.24 newton; Mann-Whitney U test, two-tailed; p< .05; n = 17 fragments); 6. There is a significant difference between edge radii r (expressed in microns μ) of serrations of three classes of tyrannosaur teeth: unerupted/partially erupted (x̄ = 78.2μ), vs. fully erupted but still attached to bone (x̄ = 94.7μ), vs. shed (x̄ = 139.3μ) teeth (two factor analysis of variance, F(2,173) = 10.86; p< .05). Teeth of Judith River tyrannosaurs possess numerous structures, both interior and exterior (see figure) whose geometry differs markedly from that of, e.g., troodon teeth (which may possess a radix, but no other differentiated internal structures), or thecodont teeth (which possess a peak of interior enamel intruding into each denticle and tilted toward the point of the tooth). Statistical anatomy of teeth may offer a rich source of information for studying taxonomy, evolution, and migration of tyrannosaurs.