There were no carnivorous sauropods, all were strictly herbivores. Their diets consisted mainly of leaves and conifer needles along with a variety of aquatic vegetation. Sauropods are thought to have balanced on their huge tails and hind legs which allowed them to reach the best leaves and needles which grew at the tops of the trees. In order to provide a steady supply of nutrients to their immense bodies it was necessary for sauropods to eat almost constantly. They needed huge stomachs to store the harder to digest material so that they could keep up with this need to feed. To aid in the digestion of the tougher vegetation they also made use of gastroliths(stomach stones) much like modern chickens do. (Image courtesy of When Dinosaurs Ruled the World).