The predentary is an 'extra' bone in the front of the lower jaw, which extended the dentary (the main lower jaw bone). It is found in the fossilised remains of ornithischian dinosaurs, which were herbivorous. The predentary coincided with the premaxilla in the upper jaw. Together they formed a beak-like apparatus used to clip off plant material. In ceratopsian dinosaurs, it opposes the rostral Human jaw front view Human jaw left view Human jaw top view The jaw is either of the two opposable structures forming, or near the entrance to, the mouth. ... Three small ammonite fossils, each approximately 1. ... Suborders Thyreophora Cerapoda    Ornithopoda    Marginocephalia Ornithischia is an order of beaked, herbivorous dinosaurs. ... Orders & Suborders Saurischia Sauropodomorpha Theropoda Ornithischia Thyreophora Ornithopoda Marginocephalia Dinosaurs were vertebrate animals that dominated the terrestrial ecosystem for over 160 million years, first appearing approximately 230 million years ago. ... A deer and two fawns feeding on some foliage A herbivore is often defined as any organism that eats only plants[1]. By that definition, many fungi, some bacteria, many animals, about 1% of flowering plants and some protists can be considered herbivores. ... The premaxilla is a pair of small bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. ... Human jaw front view Human jaw left view Human jaw top view The jaw is either of the two opposable structures forming, or near the entrance to, the mouth. ... The beak—otherwise known as the bill or rostrum—is an external anatomical structure which serves as the mouth in some animals. ... Groups Psittacosaurus Coronosauria Ceratopia (ser-a-TOP-ee-ah) or Ceratopsia is a group of ornithischian dinosaurs which evolved during the Cretaceous period in what is now North America and Asia. ...