Sauropod

Sauropods (sauro- + -pod, "lizard-footed"), are an infraorder of saurischian ("lizard-hipped") dinosaurs. They had very long necks, long tails, small heads (relative to the rest of their body), and thick, pillar-like legs. They are notable for the enormous sizes attained by some species, and the group includes the largest animals to have ever lived on land. First appearing around 250 million years ago in the Triassic Period, they were all but replaced by Titanosaurs by the Late Cretaceous, 100 million years ago.