Ouranosaurus

*Ouranosaurus nigeriensis*

***Ouranosaurus*** was an Early Cretaceous iguanodont hadrosauriform. It was unique because it had a hadrosaur-like bill and a sail on its back, like *Dimetrodon* or *Spinosaurus*. This trait is not known in any other iguanodonts or hadrosauriforms besides *Morelladon*.

It was about 23 feet (7 m) long and may have weighed about 2 tons.

## Description

### Size

*Ouranosaurus* was 23 feet long and weighed 2 metric tons. The femur is 811 millimetres long.

### Sail

*Ouranosaurus* had a large ridge on its back, held up by long, wide, spines about a half a meter in length, that spanned its whole rump and tail, like that of *Spinosaurus*, a well-known meat-eating dinosaur that appeared not long after *Ouranosaurus* disappeared. These tall spines did not look much like those of sail-backs such as *Dimetrodon* of the Permian Period. The supporting spines in a sailback get thinner distally, while in *Ouranosaurus* the spines get thicker distally and flatten. The rear spines were also bound together by ossified tendons, which made the back stiff. Finally, the spine length peaks over the forelimbs.

The sail could have been used to control body temperature or for display. Some think that the back might have had a hump, like that of a bison or camel, not a sail. It could have been used to store energy for a lean season.

### Skull

Ouranosaurus had a skull 67cm long. The head was long and flat. Its snout was toothless and much longer than that of its relative Iguanodon.

## History

Two almost complete *Ouranosaurus* fossils were found in the southern Sahara Desert, in northeast Niger, in 1966. *Spinosaurus*, a large, sail-backed meat-eater, was one of its contemporaries in the hot, Cretaceous environment of north Africa. *Ouranosaurus* was named by the French paleontologist Phillippe Taquet in 1976.

## Classification

Taquet first assigned *Ouranosaurus* to the Iguanodontidae, in the larger Iguanodontia. But, while it shares some traits of *Iguanodon* (such as a thumb spike), *Ouranosaurus* is no longer placed in the iguanodontid family. It is now placed in the clade Hadrosauroidea, which contains the Hadrosauridae (aka "duck-billed dinosaurs") and their close relatives.

## JPInstitute.com Description

Ouranosaurus was a cousin to the better known Iguanodon. There was one big difference between the two, however, in the way that these dinosaurs looked. Ouranosaurus had long spines along its back, some up to two feet long. These probably supported a fin that ran all the way down its tail, almost to the tip.

A nearly complete skeleton of Ouranosaurus was discovered in Niger in 1976, providing an excellent look at this unique African dinosaur. Other than its long neural spines, it had similar characteristics to other iguanodontids - thumb spikes, beak, etc.

## Links

http://web.archive.org/web/20040214160206fw\_/http://www.jpinstitute.com/dinopedia/dinocards/dc\_ouran.html

## References

1. ↑ Paul, G.S., 2010, *The Princeton Field Guide to Dinosaurs*, Princeton University Press p. 292
2. ↑ Template:Cite book
3. ↑ Bailey, J.B. (1997). "Neural spine elongation in dinosaurs: sailbacks or buffalo-backs?". *Journal of Paleontology* **71**: 1124-1146