Ouranosaurus

Ouranosaurus Temporal range: Early Cretaceous, 125–112 Ma PreЄ Є O S D C P T J K Pg N
Mounted skeleton cast, ROM
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Dinosauria
Order:	†Ornithischia
Suborder:	†Ornithopoda
Clade:	†Styracosterna
Clade:	†Hadrosauriformes
Genus:	†Ouranosaurus Taquet, 1976
Species:	†O. nigeriensis
Binomial name
Ouranosaurus nigeriensis Taquet, 1976

Ouranosaurus (meaning "brave (monitor) lizard") is a genus of herbivorous iguanodont dinosaur that lived during the early Cretaceous (late Aptian age) at some point between 125 and 112 million years ago, in what is now Africa. Ouranosaurus measured about 7 to 8.3 metres (23 to 27 ft) long. Two rather complete fossils were found in the Echkar (or El Rhaz) Formation, Gadoufaoua deposits, Agadez, Niger, in 1965 and 1972. The animal was named in 1976 by French paleontologist Philippe Taquet; the type species being Ouranosaurus nigeriensis.

Ouranosaurus was a relatively large euornithopod. Taquet in 1976 estimated the body length at 7 metres (23 feet), the weight at 4 tonnes (4.4 short tons). Gregory S. Paul in 2010 gave a higher length estimate of 8.3 metres (27 feet) but a lower weight of 2.2 t (2.4 short tons), emphasizing that the animal was relatively light-built. The femur is 811 millimetres (2.661 ft) long.

The most conspicuous feature of Ouranosaurus is a large "sail" on its back, supported by long, wide, neural spines, that spanned its entire rump and tail, resembling that of Spinosaurus, a well-known meat-eating dinosaur that lived around the same time. These tall neural spines did not closely resemble those of sail-backs such as Dimetrodon of the Permian Period. The supporting spines in a sailback become thinner distally, whereas in Ouranosaurus the spines actually become thicker distally and flatten. The posterior spines were also bound together by ossified tendons, which stiffened the back. Finally, the spine length peaks over the forelimbs.