Sauropods shared a 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, often whiplike tail. A massive hip girdle was fused to the backbone, usually by five sacral vertebrae; this arrangement provided solid support for the body and tail. The backbone itself was hollowed out at the sides, which thus reduced its weight while retaining structural strength. Sauropods were once thought to have spent their time wallowing in shallow water that would help support their ponderous bodies, but considerable evidence indicates that they were better equipped for living on solid ground. The animals' long necks enabled them to take foliage from even the tallest trees in somewhat the same manner as do modern giraffes (giraffe). Their teeth tended to be spoon-shaped or pencil-shaped, and they apparently depended on swallowed stones or bacteria in the gut to help break down the plant matter they ate.

Sauropods first evolved in the Early Jurassic Period (200 million to 176 million years ago). They became gigantic and highly diverse in the Late Jurassic Period (161 million to 146 million years ago) and persisted into the Cretaceous Period (146 million to 66 million years ago).