A large gap , called a diastema , separated these premaxillary teeth from the those of the maxilla ( the main upper jaw bone ) in many ornithischians , but this diastema was characteristically arched in heterodontosaurids .
A large gap , called a diastema , separated the premaxillary teeth from the those of the maxilla ( the main upper jaw bone ) in many ornithischia , but this diastema was arched in heterodontosaurs .