The plant-eater Ouranosaurus, a close relative of the very common Iguanodon, and many similar large dinosaurs walked mostly on two legs. Ouranosaurus was different because it had a large sail-like crest down its back. The purpose of this crest is not certain, although as this animal lived in hot regions the crest may have been used as a heat regulator. A similar dinosaur was Spinosaurus, a typical meat-eater which had a crest 1.8 m high running down its back. It was a very large predator, about 12 m long and weighing nearly four tonnes. Spinosaurus would have been rather unwieldy as a hunter, so it may have scavenged the carcasses of dead animals.
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