 The skull was structured in such a way that as it closed , the bones holding the teeth in the upper jaw would bow out . This would cause the lower surfaces of the upper jaw teeth to rub against the upper surface of the lower jaw 's teeth , grinding anything caught in between and providing an action that is the rough equivalent of mammalian chewing . Because the teeth were always replaced , the animal could have used this mechanism throughout its life , and could eat tough plant material . Additionally , the front ends of the animal 's jaws were toothless and tipped with bony nodes , both upper and lower , providing a rough margin that was likely covered and lengthened by a <unk> material to form a <unk> beak for biting off twigs and shoots . Its food gathering would have been aided by its flexible little finger , which could have been used to manipulate objects , unlike the other fingers . 
