Ouranosaurus
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 Ouranosaurus nigeriensis
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| Ouranosaurus nigeriensis Taquet, 1976 |
Ouranosaurus (meaning "brave (monitor) lizard") was an unusual iguanodont that lived during the early Cretaceous (early Aptian) about 110 million years ago in what is now Africa. Ouranosaurus measured about 7 m (24 ft) long and weighed about 4 tons. Two complete fossils were found in the Echkar (or El Rhaz) Formation, Gadoufaouna deposits, Agadez, Niger, in 1966 and the animal was named in 1976 by French paleontologist Philippe Taquet.
Ouranosaurus was once believed to have had a large sail on its back, supported by thick long spines, that spanned its entire back and tail, like Spinosaurus, a well-known meat-eating dinosaur that lived around the same time. In fact, the tall neural spines did not resemble those of other sail-backs such as Spinosaurus at all. The supporting spines in a sailback become thinner distally, whereas in Ouranosaurus the spines actually become thicker distally. The spines were also bound together by tendons, which stiffened the back. Finally,the spine length peaks over the forelimbs. All of these features indicate that the dinosaur could not have had a sail but in fact had a hump, resembling that of a bison, rather than a sail**.
The hump may have served as a store of fat or water useful for life in a seasonal, arid area. It may also have served as a store of fat or water for long migrations, or may have strengthened the forelimbs for more economical long-distance travelling. It is also possible it was for intimidatory purposes, making the animal look bigger than it really was, to deter rivals or predators.
On each hand it bore a thumb claw that was much smaller than the thumb claw of Iguanodon. It had an unusual head with a much longer snout that its close relative Iguanodon and that resembled a hadrosaur, a duckbilled dinosaur.
Ouranosaurus was an herbivore that had no teeth in the front portion of its jaws, but had large batteries of teeth on the sides of the jaws used to chew up plant food with its sharp beak.
[edit] Classification
Although it shares some similarities with Iguanodon (such as a thumb spike), Ouranosaurus is closer to the line of Hadrosaurids, though it is not a true hadrosaur. It may or may not be a hadrosauroid, something more closely related to hadrosaurs than to iguanodon. However there are so many similar animals that could come under this term that hadrosaur ancestry is hard to define. Most likely, Ouranosaurus was an early specailised offshoot. The type species is Ouranosaurus nigeriensis.
[edit] References
- Taquet, P. 1976. "Geologie et paleontologie du gisement de Gadoufaoua (Aptien du Niger)", Cahier Paleont., C.N.R.S. Paris, 1-191.
- Bailey, J.B. (1997). Neural spine elongation in dinosaurs: sailbacks or buffalo-backs? J. Paleontol. 71: 1124-1146.
