The giant four-legged plant-eaters make up the group called sauropods – the lizard-feet dinosaurs.
They all had small heads, long necks and barrel-shaped bodies. Some of them could crane their necks up high, although some, like Diplodocus, probably could not. In any case, holding a head up high would have put a huge strain on the heart, as it would then have had to pump blood over ten metres high.
These sauropods had to live in the open plains as they were too big to walk among the trees.
