Neornithischia was first named by Cooper in 1985 and defined as "all genasaurians more closely related to Parasaurolophus walkeri than to Ankylosaurus magniventris or Stegosaurus stenops".
The classification Neornithischia was first established by Cooper in 1985, and it is defined as comprising all genasaurians that exhibit a closer genetic relationship with Parasaurolophus walkeri than with Ankylosaurus magniventris or Stegosaurus stenops.