The Neornithischia is a clade of dinosaurs that includes the ornithopods and the marginocephalians. It’s the sister group of Thyreophora. Basal members of this clade are colliqually known as the “hypsilophodonts”, such as thelescosaurids, but these taxa do not form a valid clade.
Classification[]
It was named by Cooper in 1985 and defined as “all genasaurians closer related to Parasaurolophus than to Ankylosaurus”. It was reevaluated in 2021 to mean “the largest clade including Iguanodon and Triceratops, but not Ankylosaurus and Stegosaurus.”
In 2017, a study conducted by Matthew G. Baron, David B. Norman, and Paul M. Barrett showed that Lesothosaurus was the most basal member of the group. But Baron would later reveal that this might not be the case.
The smaller clade Pyrodontia was named in 2024 by André O. Fonseca to consist of the members of Thescelosauridae, Ceratopsia, and Ornithopoda; the clade Cerapoda was named by Paul Sereno, and is a lower classification inside Neornithischia and Pyrodontia as a combination of the latter two.