1. Superclass comprising all vertebrates with true jaws.

2. (phylum Echinodermata, class Echinoidea) Superorder of echinoids, in which the periproct is outside the apical system, there are no compound ambulacral plates, a lantern (see aristotle’s lantern) and girdle are present, and the teeth are keeled. It includes the orders Holectypoida (Jurassic–Recent), and Clypeasteroida (sand dollars, Palaeocene–Recent).