Theropod teeth from the Judith River Formation of southern Alberta, Canada

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Abstract Few attempts have been made in the past to identify dinosaur teeth at the species level, and consequently, many have assumed that they cannot be identified. However, a diverse assemblage of theropods from the Judith River Formation of southern Alberta have teeth that are diagnostic at the family, subfamily, generic, and even species levels. Within each taxon, up to four types of teeth can be recognized corresponding to the premaxillary, maxillary, anterior dentary, and posterior dentary regions. Overall tooth shape, cross sections, the position of anterior and posterior carinae, and the morphology of the denticles can be used to identify theropod taxa, regardless of absolute size or maturity. The teeth of Dromaeosaurus, Saurornitholestes, Troodon , tyrannosaurids, and a new genus and species of theropod are described. The identification of theropod teeth has the potential of refining stratigraphic determinations, extending temporal and geographic ranges, indicating relationships, and allowing paleoecological statements to be made on the relative diversity or abundance of certain taxa. Introduction Vertebrate paleontologists realized early in the development of the science that certain types of dinosaur teeth were distinctive enough to be diagnosed at the species level (Leidy 1856, 1860, 1868; Cope 1876a,b; Marsh 1892). As better specimens were recovered, many of these tooth genera proved to be nomen dubium. Perhaps the most famous example is that of Trachodon mirabilis , a species established on the basis of isolated teeth from the Late Cretaceous of Montana (Leidy 1856).