in hadrosaurs and ceratopsians) comprised a total of more than 500 active and replacement teeth. Dental batteries erupted in unison, not each column individually. The enamel on the teeth of Nigersaurus was highly asymmetrical, ten times thicker on the outwards facing side than on the inner side. This condition is otherwise known only in advanced ornithischians. Nigersaurus did not exhibit the same modifications seen in the jaws of other dinosaurs with dental batteries, or mammals with elaborate chewing functions. The lower jaw was L-shaped and divided into the subcylindrical transverse ramus, which contained the teeth, and the back ramus, which was more lightweight and was the location for most of the muscle attachments. It was distinct in that the tooth row expanded to the sides from the plane of the main ramus of the lower jaw. The jaws also contained several fenestrae, including five that are not present in other sauropods. The front ends of the jaws had grooves that indicate the presence of a keratinous (horny) sheath. Nigersaurus is the only known tetrapod animal to have had jaws wider than the skull and teeth that extended laterally across the front. The snout was even broader than those of the "duck-billed" hadrosaurs. Postcranial skeleton Nigersaurus was distinct in that its (back) vertebrae had paired pneumatic spaces at the base of the (the spines that projected upwards from the vertebrae). The presacral vertebrae (vertebrae in front of the sacrum) were heavily pneumatised to the point where the column consisted of a series of hollow "shells", each divided by a thin septum in the middle. It had little to no cancellous bone, making the centra thin bone plates filled with air spaces. The vertebral arches were so heavily pierced by extensions of the external air sacs that of their side walls little remained but thick intersecting laminae, the ridges between the pneumatic openings. The vertebrae of the tail, however, did have solid centra. The pelvic and pectoral girdle bones were very thin also, often only several millimetres thick. It had a prominent rugosity (a roughly wrinkled area) on the midline aspect of the scapular blade's base, a distinguishing feature. Like other sauropods, its limbs were robust, contrasting with the extremely lightweight construction of the rest of the skeleton. The limbs were not as specialised as the rest of the skeleton, and the front legs of Nigersaurus were about two-thirds the length of