The ornithischian dinosaurs were the most numerous and diverse of the Cretaceous period dinosaurs. Similar to the ornithischian dinosaurs of the Jurassic period, these dinosaurs were all members of the clade called the Genasauria: beaked, herbivorous dinosaurs that were the prey for carnivorous theropods. In one frequently used classification, the Genasauria are divided into the Neornithischia and Thyreophora. The Thyreophora are further divided into the Stegosauria and the Ankylosauria (although in some classifications, these two divisions are combined into one group; in another classification, Eurypoda is added with the Stegosauria and Ankylosauria); the Neornithischia are divided into several types of dinosaurs, the major one being the Ceropoda, which include the Ornithopoda and the Marginocephalia.