 On the other hand, ornithopods such as "Hypsilophodon", "Iguanodon" and various hadrosaurs had horny beaks for snipping off vegetation and jaws and teeth that were well-adapted for chewing.The horned ceratopsians had similar mechanisms.It has often been suggested that at least some dinosaurs used swallowed stones, known as gastroliths, to aid digestion by grinding their food in muscular gizzards, and that this was a feature they shared with birds.