Mounted Ouranosaurus skeleton, Museo di Storia Naturale di Venezia (*)
Ouranosaurus (meaning "brave (monitor) lizard") was an unusual iguanodont that lived during the early Cretaceous (late Aptian stage) about 110 million years ago in what is now Africa. Ouranosaurus measured about 7 meters long (24 ft) 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.
On each hand it bore a thumb claw that was much smaller than the thumb claw of the earlier Iguanodon. The second third digits were broad and hoof-like, and anatomically were good for walking. To support the walking hypothesis, the wrist was large and the bones fused together to prevent its dislocation. The last digit (number 5) was long and presumably used for picking food like leaves and twigs or to help lower the food by lowering branch to a manageable height.
The hindlimbs were large and solid to accommodate the weight of the body. The femur was longer than the tibia, and the foot was small with only three toes. This leads to a conclussion of the legs being used as pillars and not for sprinting.
It had an unusual head with a much longer snout that its close relative Iguanodon; the snout was covered in a horny sheath when alive. The nasal passage was large and placed close to the beak. An anomaly with the skull were bumps found from the nasal opening to the top of the skull; their significance is unknown but they may have been used for socialisation or mating practices.
Ouranosaurus was an herbivore that had no teeth in the front portion of its jaws but a beak as in ducks and platypus. But the jaw teeth were large batteries of teeth on the sides of the jaws with Ouranosaurus used to chew up plant food with its sharp beak. The jaw also contained a predentary bone at the extreme front.
Temporal openings were found behind the eye and the larger Capiti-mandibularis muscle was attached to the coronid process on the jaw bone. The coronid process provided for a greater area of attachment for the jaw muscle allowing for more power and a stronger bite. A lesser muscle is located at the back of the skull and is named the Depressor mandibulae.
Life restoration of Ouranosaurus nigeriensis (*)
Although it shares some similarities with Iguanodon (such as a thumb spike), Ouranosaurus is no longer placed in Iguanodontidae, a grouping that is now considered paraphyletic. It is instead placed in the clade Hadrosauroidea, which contains the true hadrosaurs ("duck-billed dinosaurs") and their closest relatives. Ouranosaurus appears to have been an early specialised offshoot in this group. The type species is Ouranosaurus nigeriensis.
* Taquet, P. 1976. "Geologie et paleontologie du gisement de Gadoufaoua (Aptien du Niger)", Cahier Paleont., C.N.R.S. Paris, 1-191.