This chapter examines the evolutionary relationships of sauropods using cladistic analysis. It also describes in the detail their paleobiology, taphonomy, and paleoecology. Sauropod dinosaurs include the largest terrestrial animals ever to have existed. At present, Sauropoda comprises twenty-two genera. Sauropods have small skulls in relation to their body size, extremely elongate necks and tails, columnar limbs, and stout, barrel-shaped bodies. Sauropod remains have been recovered from all continents except Antarctica. They are found in mass accumulations (bone beds) in the Morrison Formation of the western United States, in the Tendaguru Beds of East Africa, in the Kota Formation of India, in the Lower Shaximiao Formation of the Sichuan Basin in China, and in the Cañodon Asfalto Formation of Patagonia.