Ouranosaurus (Greek for "brave lizard"); pronounced ore-ANN-oh-SORE-us
Plains of northern Africa
Middle Cretaceous (115-100 million years ago)
Size and Weight:
About 23 feet long and four tons
Row of spines jutting out from backbone; horned beak
Once considered to be a close relative of Iguanodon, paleontologists have now classified Ouranosaurus as a type of hadrosaur (duck-billed dinosaur)--albeit one with a major difference. This plant-eater had rows of spines jutting out vertically from its backbone, which has fueled speculation that it may have sported a sail of skin, like the contemporary Spinosaurus or the much earlier pelycosaur Dimetrodon. However, some paleontologists maintain that Ouranosaurus didn't have a sail at all, but a flattened hump, rather like that of a camel.
If Ouranosaurus did in fact possess a sail (or even a hump) the logical question is, why? As with other sailed reptiles, this structure may have evolved as a temperature-regulation device (assuming that Ouranosaurus had a cold-blooded rather than a warm-blooded metabolism), and it may also have been a sexually selected characteristic (that is, Ouranosaurus males with bigger sails had the opportunity to mate with more females). A fatty hump, on the other hand, might have served as a valuable reserve of food and water, the same function as it serves in modern camels.
One lesser-known feature of Ouranosaurus is the shape of this dinosaur's head: it was unusually long and flat for a hadrosaur, and lacking any of the ornamentation of later duck-billed dinosaurs (such as the elaborate crests of Parasaurolophus and Corythosaurus) save for a slight ridge over the eyes. Like other hadrosaurs, the four-ton Ouranosaurus may have been capable of running away from predators on its two hind feet, which presumably would have imperiled the lives of any smaller theropods or ornithopods in the immediate vicinity!