Heterodontosaurids are named for their strongly heterodont dentition. 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'. A lower caniniform, larger than the upper, took the first position in the dentary and was accommodated by the arched diastema of the upper jaw when the mouth was closed. These caniniforms were serrated on both the anterior and posterior edges in "Heterodontosaurus" and "Lycorhinus", while those of "Abrictosaurus" bore serrations only on the anterior edge. In the Early Cretaceous "Echinodon", there may have been two upper caniniforms, which were on the maxilla rather than the premaxilla, and "Fruitadens" from the Late Jurassic may have had two lower caniniforms on each dentary.