Neornithischia

Neornithischians Temporal range: Middle Jurassic–Late Cretaceous, 170–66 Ma PreꞒ Ꞓ O S D C P T J K Pg N (possible Early Jurassic record)
Six neornithischians (top left to bottom right): Psittacosaurus, Styracosaurus, Thescelosaurus, Kulindadromeus, Hypacrosaurus, Pachycephalosaurus
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	†Ornithischia
Clade:	†Genasauria
Clade:	†Neornithischia Cooper, 1985
Subgroups[1]
Agilisaurus Gongbusaurus? wucaiwanensis Hexinlusaurus Lesothosaurus? Minimocursor Nanosaurus Phyllodon Sanxiasaurus Xiaosaurus Yandusaurus Pyrodontia Fonseca et al., 2024[1] Kulindadromeus Laosaurus? minimus Thescelosauridae Cerapoda Sereno, 1986 Siluosaurus Marginocephalia Ornithopoda

Neornithischia ("new ornithischians") is a clade of the dinosaur order Ornithischia. It is the sister group of the Thyreophora within the clade Genasauria. Neornithischians are united by having a thicker layer of asymmetrical enamel on the inside of their lower teeth. The teeth wore unevenly with chewing and developed sharp ridges that allowed neornithischians to break down tougher plant food than other dinosaurs. Neornithischians include a variety of basal forms historically known as "hypsilophodonts", including the Parksosauridae; in addition, there are derived forms classified in the groups Marginocephalia and Ornithopoda. The former includes clades Pachycephalosauria and Ceratopsia, while the latter typically includes Hypsilophodon and the more derived Iguanodontia.