The Ceratopsians were the animals that include Triceratops. They have large frills that are normally hollow, and walk on four legs. They eat plants with a very powerful beak that can also be used as a weapon. Some of them have horns that make for a great defense. By charging like a rhino, the Ceratopsians could cause some serious damage to anything they hit. Not all of them are big or have horns, and thier subfamily the Protoceratopsians fit that description perfectly.. The ceratopsian above is Pentaceratops.