Ouranosaurus (Ouranosaurus nigeriensis) is a genus of herbivorous dinosaur belonging to the family Ouranosauridae. It lived approximately 112 to 110 million years ago in what is now Niger, Africa. The first fossils of Ouranosaurus were discovered in the early 1960s, and subsequent excavations have revealed a wealth of well-preserved specimens.

Ouranosaurus possessed a unique feature that sets it apart from other dinosaurs – a long and distinctive sail-like structure on its back. This sail was formed by elongated spines extending from the vertebrae, possibly supported by a network of skin or muscle. The sail could have served various functions, including thermoregulation, species recognition, or display during courtship. Ouranosaurus had a slender body, measuring approximately 6 to 7 meters in length, and it stood on powerful hind limbs, suggesting bipedal locomotion. Its head was adorned with a beaked snout and a battery of leaf-shaped teeth adapted for feeding on vegetation.