Ouranosaurus is a genus of herbivorous iguanodontdinosaur that lived during the Aptian stage of the Early Cretaceous of modern-day Niger. Ouranosaurus measured about 7 to 8.3 metres (23 to 27 ft) long. Two rather complete fossils were found in the Elrhaz Formation, Gadoufaoua deposits, Agadez, Niger, in 1965 and 1970. The animal was named in 1976 by French paleontologist Philippe Taquet; the type species being Ouranosaurus nigeriensis. The name is a combination of the Arabic word for “courage” and the country of discovery, although ourane is also the Tuareg name for the desert monitor.
Ouranosaurus was a relatively large iguanodontian, estimated by Taquet in 1976 to have a body length of 7 metres (23 feet) and a weight of 4 tonnes (4.4 short tons). A lighter weight of 2.2 tonnes (2.4 short tons) was suggested by American palaeontologist Gregory S. Paul in 2010 due to the although a longer length of 8.3 m (27 ft) was given. The holotype and paratype specimens were suggested to belong to subadults by Bertozzo et al. in 2017, although they would have been close to adult size. MSNVE 3714 is 6.5 m (21 ft) long as mounted, although a few caudals are missing, and is roughly 90% the length of the holotype, which would be 7.22 m (23.7 ft) long. The variation between the sizes fits within the range of variation between adult individuals of Iguanodon, so there is a chance that the larger holotype and smaller paratype were same ontogenetic stage.
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 ornamentations 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!
Also read: 10 Cool Facts About Giganotosaurus