 These were a large , heavily built , herbivorous quadrupeds with rounded backs , short fore limbs , long hind limbs , and tails held high in the air . Due to their distinctive combination of broad , upright plates and tail tipped with spikes , Stegosaurus is one of the most recognizable kinds of dinosaur . The function of this array of plates and spikes has been the subject of much speculation among scientists . Today , it is generally agreed that their spikes were most likely used for defense against predators , while their plates may have been used primarily for display , and secondarily for thermoregulatory functions . Stegosaurus had a relatively low brain @-@ to @-@ body mass ratio . It had a short neck and a small head , meaning it most likely ate low @-@ lying bushes and shrubs . One species , Stegosaurus ungulatus , is the largest known of all the stegosaurians ( bigger than related dinosaurs such as Kentrosaurus and Huayangosaurus ) . 
