A supernumerary tooth in a 1.7 million-year-old Australopithecus robustus from Swartkrans, South Africa.

The maxillary dental arch of a partial cranium of an adult specimen of Australopithecus robustus shows the presence of a supernumerary tooth between the right first and second incisors. The fossil specimen, SK 83, is from Swartkrans Member 1 sediments, considered, on the basis of associated fauna, to be approximately 1.7 million yr old. The specimen was analyzed macroscopically, stereomacroscopically and by X-ray computed tomography. The anatomic position and the morphology of the tooth are consistent with a diagnosis of supernumerary lateral incisor rather than a mesiodens or a retained deciduous tooth. This is the first description of a supernumerary tooth found in Plio-Pleistocene hominid fossils from South African cave deposits.