Diplodocus (Diplodocus longus), artwork. This species of dinosaur lived during the Jurassic, 150 million years ago. It belongs to the sauropod group of extinct animals which were the largest animals to have lived on land. Diplodocus is estimated to have grown to a length of 35 metres, of which over 6 metres was neck length. It had a tiny skull in comparison to its body and a long tail containing 80 caudal vertebrae. Early reconstructions depicted Diplodocus and other sauropods with necks held high in the air. Recent studies show that a horizontal neck is the more likely posture.