 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.Like the characteristic tusks, the cheek teeth of derived heterodontosaurids were also unique among early ornithischians.