The teeth wore unevenly with chewing and developed sharp ridges that allowed neornithischians to break down tougher plant food than other dinosaurs.

[3] In 2021, Neornithischia was given a formal definition under the PhyloCode: "The largest clade containing Iguanodon bernissartensis and Triceratops horridus but not Ankylosaurus magniventris and Stegosaurus stenops.

[7] In 2021, Cerapoda was given a formal definition under the PhyloCode: "The smallest clade containing Iguanodon bernissartensis Boulenger in Beneden, 1881, Pachycephalosaurus wyomingensis (Gilmore, 1931), and Triceratops horridus Marsh, 1889.

[1] Asilisaurus Lutungutali Silesaurus Technosaurus Kwanasaurus Eucoelophysis Pisanosaurus Heterodontosauridae Eocursor Laquintasaura Lesothosaurus Emausaurus Scutellosaurus Scelidosaurus Yuxisaurus Jakapil Eurypoda Agilisaurus Hexinlusaurus Sanxiasaurus Minimocursor Yandusaurus Nanosaurus Zephyrosaurus Orodromeus Oryctodromeus Albertadromeus Koreanosaurus Yueosaurus Changmiania Haya griva

Changchunsaurus Jeholosaurus Parksosaurus Thescelosaurus Kulindadromeus Pachycephalosauria Ceratopsia Hypsilophodontidae Rhabdodontomorpha Anabisetia Diluvicursor Gasparinisaura Notohypsilophodon Elasmaria Iyuku Dryomorpha