 The long and narrow skull was small in proportion to the body . It had a small antorbital fenestra , the hole between the nose and eye common to most archosaurs , including modern birds , though lost in extant crocodylians . The skull 's low position suggests that Stegosaurus may have been a browser of low @-@ growing vegetation . This interpretation is supported by the absence of front teeth and their likely replacement by a horny beak or rhamphotheca . The lower jaw of Stegosaurus had a flat upward extension that would have completely hidden the teeth when viewed from the side , and which probably supported a turtle @-@ like beak in life . Other researchers have interpreted these ridges as modified versions of similar structures in other ornithischians which might have supported fleshy cheeks , rather than beaks . <unk> teeth were small , triangular , and flat ; wear facets show that they did grind their food . The jaws of Stegosaurus had flat downward and upward extensions that would have completely hidden the teeth when viewed from the side , and these probably supported a beak in life . The presence of a beak extended along much of the jaws may have precluded the presence of cheeks in these species . Such an extensive beak was probably unique to Stegosaurus and some other advanced stegosaurids among ornithischians , which usually had beaks restricted to the jaw tips . 
