Digesting plant matter is a much more intensive biochemical process than digesting meat. This herbivore swallowed gastroliths (gizzard stones) to help break down the food in its stomach. Herbivorous dinosaurs needed a huge gut. Since this had to be positioned in front of the pelvis, balancing on two legs became increasingly difficult, as dinosaurs became larger and they gradually evolved into the quadrupedal position that characterizes the later sauropods such as "Diplodocus". Prosauropods represented a middle phase between the earliest bipedal herbivores and the later giant sauropods. As a prosauropod, "Anchisaurus" was mostly typical of this group, which flourished briefly during the late Triassic and early Jurassic. "Anchisaurus" teeth, used to rip food, were shaped like spoons. It had fewer and more widely spaced teeth than true prosauropods, and as Peter Galton and Michael Cluver observed, narrower feet. "Anchisaurus" would have spent most of its time on four legs but could have reared up on its hind legs to reach higher plants.