Complete your tour of dinosaur groups with the species of Ornithischia, a large family of herbivores that feature striking anatomy. Get to know the subgroups of Ankylosauria, with their armor and tail clubs; Stegosauria, known for dorsal plates and spikes; Ceratopsia, sporting eye and nose horns, and frills; Pachycephalosauria, the bone-headed dinosaurs; and Ornithopoda, the duck-billed species.