A Subadult Frontal of Daspletosaurus torosus (Theropoda: Tyrannosauridae) from the Late Cretaceous of Alberta, Canada with Implications for Tyrannosaurid Ontogeny and Taxonomy

Abstract

An isolated frontal bone of Daspletosaurus torosus (Theropoda: Tyrannosauridae) is desecribed which was probably found in the Dinosaur Park Formation (Upper Cretaceous) of Dinosaur Provincial Park, Alberta (Canada). It is important in terms of the first detailed osteological description of the frontal of Daspletosaurus torosus. The size and anatomical details of the specimen indicates the frontal belongs to a large subadult individual. This subadult frontal suggests that although ontogeny of Daspletosaurus torosus was generally similar to that of Tyrannosaurus rex, there were some distinct differences. Finally, certain features of this frontal bone indicate that some autapomorphies that have recently suggested for some tyrannosaurid taxa are inadequate due to their broad distribution within a clade.