Q What do we call the group of dinosaurs characterized by their horns and neck frills?

Horned dinosaurs (ceratopsians) are characterized by the horns on their heads, their neck frills, and their curved, parrot-like beaks.
In primitive horned dinosaurs, however, these horns and frills were not very prominent.
Additionally, the rostral bone at the tip of the upper jaw is a unique feature that evolved exclusively in this group of dinosaurs.