"Scelidosaurus" and its Jurassic relatives were herbivorous. Other ornithischians had teeth capable of grinding plant material, but "Scelidosaurus" had smaller, less complex teeth. Its jaw could only do simple up-and-down movements. In this aspect, they resembled the stegosaurids, which also had primitive teeth and simple jaws. Also, like stegosaurs, they may have swallowed gastroliths to aid processing of food (because of the lack of chewing ability). This is also done by modern birds and crocodiles. The diet of "Scelidosaurus" was low-lying plants (like cycads) and probably also fruits. Seaweeds have also been suggested as its food. Grass did not evolve until the Cretaceous period.