Heterodontosaurids are called that because they have two different kinds of teeth. There were three premaxillary teeth. In the early Jurassic "Abrictosaurus", "Heterodontosaurus", and "Lycorhinus", the first two premaxillary teeth were small and conical, while the much larger third tooth resembled the canines of carnivoran mammals and is often called the "caniniform" or 'tusk'. 