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oo - RAN - oh - SAW - rus
Name Means: "Brave lizard"
This early Cretaceous ornithopod from west Africa is one of the most puzzling dinosaurs ever discovered, and paleontologists are still trying to work out what it looked like. This is surprising, because Ouranosaurus is known from an almost complete skeleton - which was discovered in 1966 - and its closest known relative, Iguanadon, is one of the best understood dinosaurs of all.
The problem lies with the backbone. The neural spines - the bones that projected upward from the main part of the vertebrae and which usually supported important sets of the back muscles and tendons - were simply huge in Ouranosaurus. Imagine an animal with a chest the size of a modern racehorse's, with a set of spines more than 27 inches (0.7 m( tall along the length of its back. What function could these spines have served?
Some scientists believe that Ouranosaurus sported a huge sail-like structure on its back. "Sail-backed" animals are known from the Permian period, 260 million years ago, and it is thought that these "sails" helped them to regulate their body temperature. In some reconstructions, then, Ouranosaurus is shown as an unremarkable, medium-sized ornithopod, except for its long sail.
Others disagree with the "sail" theory. They point out that in the hot, dry climate in which it lived, Ouranosaurus would not have needed a sail to get warm. Overheating would have been more of a problem, and a sail would have been of no use in getting rid of heat. Plus, the spines of Ouranosaurus bear little resemblance to those of the Permian sail-backs. They look more like the spines that form the withers in modern mammals such as bison. Some scientists therefore reconstruct Ouranosaurus as an unusual ornithopod with a huge humped back - a kind of dinosaurian version of a camel or buffalo.