The sauropod group of dinosaurs included the largest animals ever to walk the Earth. Sauropods were plant eaters with very long necks. The giant Brachiosaurus likely ate more than 400 pounds of plants a day. The enormous Omeisaurus's neck made up more than half of the length of its entire body. Sauropods also had long tails, sometimes with dangerous spikes on them. Scientists believe the lengthy Diplodocus and other sauropods used their long tails as weapons against predators. Inside, readers will learn about these and many others long-neck herbivores.