Ceratopsians are a group of herbivorous dinosaurs known for their distinctive frills and horns on their heads. They lived during the late Cretaceous period and are part of the larger clade called Ornithischia. Some well-known ceratopsians include Triceratops and Styracosaurus, which had various horn arrangements and frill shapes. These dinosaurs were primarily quadrupedal, meaning they walked on all four legs. Ceratopsians likely used their horns and frills for defense against predators, social interactions, or mating displays. Their beak-like mouths were adapted for chewing tough plant material, making them efficient grazers in their ecosystems.