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 elaborate facial features that may have been used for display or defense. These dinosaurs varied in size, with some being as small as a dog and others as large as a truck. Ceratopsians typically walked on four legs and had beak-like mouths for cropping plants. Their fossils have been found in North America and parts of Asia, providing valuable insights into their behavior and environment.