First record of supernumerary teeth in South American fossil rodents

Abstract

Supernumerary tooth are recorded for nearly all actual groups of mammals as well as many fossil groups. In modern rodents extra tooth have been studied in several families, nevertheless its fossil record is extremely scarce. In this work we report the first case of a fossil South American rodent with a supernumerary tooth. The studied specimen is a right mandible with broken m1-m3, an extra tooth and incisive of an adult individual of Sciamys principalis (Octodontoidea, Acaremyidae) from the early Miocene of Patagonia. Based on the occlusal morphology and implantation of this supernumerary tooth, and the general characters and size of the normal m1-m3, we inferred that the appearance of the extra tooth was consequence of genetic alterations. Nevertheless we do not reject other factor as causes of its occurrence.