Ouranosaurus nigeriensis

Norman, David B., 2015, On the history, osteology, and systematic position of the Wealden (Hastings group) dinosaur Hypselospinus fittoni (Iguanodontia: Styracosterna), Zoological Journal of the Linnean Society 173 (1), pp. 92-189 : 152-153

OURANOSAURUS NIGERIENSIS TAQUET, 1975

Ouranosaurus is a well-described ornithopod from the Aptian ( Taquet, 1976) or Aptian−Albian ( Sereno et al., 1999) of Niger. Comparatively slender in build, this animal attained a length of 6–7 m when mature and is notable for the extremely elongate and expanded neural spines across its dorsal, sacral, and caudal series ( Taquet, 1975, 1976).

Teeth and jaws

The dentary teeth ( Taquet, 1976: pl. XX), although similar in general shape to those of Hy. fittoni , do not show the complexity of morphology of secondary and accessory ridges seen in the latter taxon. The dentary of O. nigeriensis ( Taquet, 1976: fig. 29) is extremely elongate, has a long edentulous region, and its ramus deepens anteriorly, and therefore differs in structure from that seen in material referred to Hy. fittoni , although the comparative size and oblique orientation of the coronoid process of the dentary is similar in both taxa.

Axial skeleton

Ouranosaurus nigerienis and Hy. fittoni can be distinguished from others by the remarkable elongation of their dorsal, sacral, and caudal neural spines; however, those of O. nigeriensis are not only extremely elongate, but widen apically to create a completely different profile ( Taquet, 1976: fig. 40) and have none of the complexity seen on the preaxial and postaxial edges in Hy. fittoni .

Appendicular skeleton

The postcranial skeletons of both taxa are generally similar although that of O. nigeriensis is more lightly constructed. The forelimb is more slender, notably the radius and ulna, but the carpometacarpal block is well developed and the pollex ungual is tall, subconical, bluntly pointed, and exhibits little curvature ( Taquet, 1976: fig. 57c). The pelvis differs from that of Hy. fittoni ( Taquet, 1976: figs 58, 59). The femur is straighter than that of Hy. fittoni ( Taquet, 1976: fig. 62) and has a less angular shaft, a laterally flattened anterior trochanter, and the extensor intercondylar groove may have been more open when compared with that of Hy. fittoni . The remainder of the hindlimb has no obviously distinguishing anatomy although the pedal unguals may be shorter, more blunt, and may lack claw grooves ( Taquet, 1976: fig. 71d).