SAUROPOD

any member of the infraorder Sauropoda (suborder Sauropodomorpha) of saurischian dinosaurs marked by large size, four-legged stance, and herbivorous diet. The sauropods were the largest of all dinosaurs and the largest land animals that ever lived. They evolved in the Late Triassic or Early Jurassic epochs (230 to 187 million years ago), reached their peak in the Late Jurassic (163 to 144 million years ago), and persisted into the Cretaceous Period (144 to 66.4 million years ago). The various species all shared a similar body plan consisting of a small head on an extremely long neck; a long, massive body housing an enormous gut; thick, pillarlike legs to support the torso; and a very long, tapering, whiplike tail. A massive hip girdle fused to the backbone by four (or in some cases five) sacral vertebrae provided solid support for the body and tail, and the backbone itself was hollowed out at the sides to lighten its weight while still retaining structural strength. Sauropods were previously thought to have spent their time wallowing in shallow water that helped support their ponderous bodies, but some species were apparently better equipped for living on hard ground. The animals' long necks enabled them to crop vegetation from even the tallest trees, in somewhat the same manner as modern giraffes. Their teeth tended to be weak and sparse, and they apparently depended on swallowed stones or bacteria in the gut to help break down the plant matter they ate. The sauropods evolved into five families: Cetiosauridae, Brachiosauridae (containing Brachiosaurus), Camarasauridae, Diplodocidae (containing Diplodocus and Apatosaurus), and Titanosauridae. The smaller sauropods reached lengths of up to 15 m (50 feet), while larger species such as Apatosaurus (formerly known as Brontosaurus) routinely reached lengths of 21 m. Brachiosaurus was one of the largest and most massive of all known dinosaurs, reaching a length of 30 m and a weight of 80 metric tons.