Heterodontosaurinae

Heterodontosaurinae is the derived, largely Gondwanan subfamily of the heterodontosaurids, a group of small, early ornithischian dinosaurs. It gathers the heterodontosaurids more closely related to Heterodontosaurus than to Tianyulong, Fruitadens, or Echinodon, and includes such genera as Heterodontosaurus, Lycorhinus, Abrictosaurus, Manidens, and Pegomastax. Its members display the most specialized heterodontosaurid jaw and tooth anatomy: whereas basal relatives kept widely spaced, low-crowned cheek teeth, these derived forms bore chisel-shaped teeth with much taller crowns that lost the ridge separating crown from root and overlapped to form a continuous surface for grinding tough plant food. This chewing apparatus, unusual among early ornithischians, foreshadowed the analogous dental batteries later evolved by hadrosaurs and ceratopsians.