Ornithopod
Ornithopoda means "bird feet", from the Greek. It refers to their three-toed feet (though many early forms had four toes). They had no armour, a horny beak, and various other features. Some ornithopods and cerapods had thin cartilaginous plates along the outside of the ribs. In some cases, these plates mineralized and so were fossilized. The function of these plates is unknown.