 In 2007, a cladistic analysis suggested that heterodontosaurids are basal to all known ornithischians except "Pisanosaurus", a result that echoes some of the very earliest work on the family.However, a study by Bonaparte found the Pisanosauridae to be synonymous with the Heterodontosauridae and not a separate family in its own right, thereby including Pisanosaurus as a heterodontosaur.Butler et al.