Any of the bird-hipped dinosaur species (order Ornithischia), herbivores with hip bones arranged like those of modern birds, with the pubis bone pointed backward. Many species had a toothless, horny beak and powerful cheek teeth. Ornithischians flourished from the Late Triassic to the Late Cretaceous Epoch (227–65 million years ago). Many species (in the suborder Cerapoda) were bipedal and had ornate skull structures. Some were quadrupedal, with a massive head culminating in a great bony frill. Other quadrupeds (in the suborder Thyreophora) had small heads and were heavily plated and armoured along the back, and some had armour on the flanks and head as well. See alsoprotoceratops; saurischian; stegosaur; triceratops.