Revisión sistemática y antigüedad de Smilodontidion riggii (Carnivora, Felidae, Machairodontinae)

Abstract

Systematic review and antiquity of Smilodontidion riggii (Carnivora, Felidae, Ma-chairodontinae). For twenty years the holotype of Smilodontidion riggii L. J. Kraglievich, supposedly recovered from Chapadmalalan beds (early Pliocene), was the oldest felid record in South America. Later, it was synonymized with Smilodon populator Lund without clear justification. The synonymizing authors stated only that it was a juvenile specimen of S. populator, and that it came from Ensenadan beds (late Pliocene–middle Pleistocene). In this paper the holotype of Smilodontidion riggii and other specimens referred to this species are reviewed, described in detail and compared with other machairodontines and large felines. The goals are to test the validity of this taxon, or its possible assignation to Megantereon Croizet and Jobert, S. gracilis Cope, S. fatalis (Leidy), or S. populator, and evaluate its age and provenance. Our review suggests that Smilodontidion is a synonym of Smilodon, although it could not be assigned to any species of the genus, and the validity of the species is not justified by the morphology of Smilodontidion riggii. The scarce and dubious geographic and stratigraphic data for MACN Pv 6802, and the information from other specimens, do not confirm a Chapadmalalan age for the taxon. Thus, the oldest South American felids are Ensenadan in age