Nigersaurus (/niːˈʒɛərsɔːrəs, ˈnaɪdʒərsɔːrəs/) is a genus of rebbachisaurid sauropod dinosaur that lived during the middle Cretaceous period, about 115 to 105 million years ago.

Unlike other tetrapods, the tooth-bearing bones of its jaws were rotated transversely relative to the rest of the skull, so that all of its teeth were located far to the front.

It is one of the most common fossil vertebrates found in the area, and shared its habitat with other dinosaurian megaherbivores, as well as large theropods and crocodylomorphs.

Remains thought to belong to Nigersaurus were first discovered during a 1965–1972 expedition to the Republic of Niger led by French paleontologist Philippe Taquet, and first mentioned in a paper published in 1976.

[1][2] Although a common genus, the dinosaur had been poorly known until more material of other individuals was discovered during expeditions led by American palaeontologist Paul Sereno in 1997 and 2000.

[1] In 2007, a more detailed description of the skeleton was published by Sereno ad colleagues, based on a specimen discovered ten years earlier.

The fossils, along with a reconstructed skeleton mount and a plastic model of the head and neck, were subsequently presented at the National Geographic Society in Washington.

He likened its physical appearance to Darth Vader and a vacuum cleaner, and compared its tooth shear with a conveyor belt and sharpened piano keys.

The vertebral arches were so heavily pierced by extensions of the external air sacs that of their side walls little remained but 2 mm (0.08 in) thick intersecting laminae, the ridges between the pneumatic openings.

It had a prominent rugosity (a roughly wrinkled area) on the midline aspect of the scapular blade's base, a distinguishing feature.

[3][4] The remains of Nigersaurus were initially described by Taquet in 1976 as belonging to a dicraeosaurid, but in 1999 Sereno and colleagues reclassified it as a rebbachisaurid diplodocoid.

The eponymous subfamily Nigersaurinae, which includes Nigersaurus and closely related genera, was named by the American palaeontologist John A. Whitlock in 2011.

[14] The closely related genus Demandasaurus from Spain was described by the Spanish palaeontologist Fidel Torcida Fernández-Baldor and colleagues in 2011, and along with other animal groups that span the Cretaceous of Africa and Europe, this indicates that carbonate platforms connected these landmasses across the Tethys Sea.

[15] This was supported in 2013 by the Italian palaeontologist Federico Fanti and colleagues in their description of the nigersaurine Tataouinea from Tunisia, which was more related to the European form than to Nigersaurus, despite being from Africa, then part of the supercontinent Gondwana.

[16] Amazonsaurus Histriasaurus Zapalasaurus Comahuesaurus Rayososaurus Rebbachisaurus Cathartesaura Limaysaurus Nigersaurus Demandasaurus Tataouinea A 2015 cladistic study by Wilsona and the French palaeontologist Ronan Allain found Rebbachisaurus itself to group with the nigersaurines, and the authors suggested that Nigersaurinae was therefore a junior synonym of Rebbachisaurinae (since that name would have priority).

[9] The same year, Fanti and colleagues supported the use of Rebbachisaurinae over Nigersaurinae, and found Nigersaurus to be the basalmost member of this "Euro-African" subclade.

[19] Though it had large nostrils and a fleshy snout, Sereno and colleagues found that Nigersaurus had an underdeveloped olfactory region of its brain and thus did not have an advanced sense of smell.

[3] The American palaeoartist Mark Hallett and paleontologist Mathew J. Wedel and stated in 2016 that while sauropods in general could use their long necks to detect predators from afar, this would not apply to the short-necked Nigersaurus.

Since several rebbachisaurids inhabited latitudes that would have been tropical to subtropical in the Middle Cretaceous, this pneumaticity may have helped the animals cope with the very high temperatures.

They also suggested that sauropods may therefore have been lighter in weight than expected for their size, supporting the lowest body mass estimates for these dinosaurs.

The width of the muzzle and lateral orientation of the tooth row show that the sauropod could gather much food and crop it close to the ground, within 1 m (3 ft 3 in) of the surface.

Nigersaurus also bears signs of low-angle tooth-to-tooth wear on the inside of the maxillary crowns, which suggests that jaw movement was limited to precise up-and-down motions.

[3] In addition, according to Whitlock and colleagues in 2011, the small, nearly parallel nature of the tooth scratches and pits (caused by grit, which would not be obtained as often by high-browsers) indicate that it ate relatively soft, herbaceous plants such as low-growing ferns.

Sereno and colleagues stated it was unlikely that Nigersaurus fed on conifers, cycads, or aquatic vegetation, due respectively to their height, hard and stiff structure, and lack of appropriate habitat.

[3] Wedel suggested that the evenly spaced teeth of Nigersaurus could have functioned like a comb, by straining water plants or invertebrates, similar to flamingos.

Based on this biomechanical analysis, the team concluded that the head and muzzle were habitually oriented 67° downwards and close to ground level, as an adaptation for ground-level browsing.

It further argued that the orientation of the semicircular canals varies significantly within modern species, and is therefore not reliable for determining head posture.

[23] This was supported by the Spanish palaeontologist Jesús Marugán-Lobón and colleagues in a 2013 study that suggested the methods used by Sereno's team were imprecise, and that Nigersaurus habitually held its head like other sauropods.

[24] In 2020, the French palaeontologist Julien Benoit and colleagues tested lateral semicircular canal correlation to head posture on modern mammals, and found that while there was significant correlation between the reconstructed and actual head postures, the plane of the semicircular canal was not held horizontally in the resting pose as inferred.

[25] Nigersaurus is known from the Elrhaz Formation of the Tegama Group in an area of the Ténéré Desert called Gadoufaoua, located in Niger.