 "Heterodontosaurus" was named in 1962 and it, "Lycorhinus" and "Geranosaurus" were recognized as closely related ornithischian dinosaurs.Alfred Romer named Heterodontosauridae in 1966 as a family of ornithischian dinosaurs including "Heterodontosaurus" and "Lycorhinus".It was defined as a clade in 1998 by Paul Sereno and redefined by him in 2005 as the stem clade consisting of "Heterodontosaurus tucki" and all species more closely related to "Heterodontosaurus" than to "Parasaurolophus walkeri", "Pachycephalosaurus wyomingensis", "Triceratops horridus", or "Ankylosaurus magniventris".