First record of Posnanskytherium (Notoungulata, Toxodontidae) in the late Neogene of eastern Puna, Argentina

Abstract

Records of the toxodontid Posnanskytherium were only known from the Pliocene levels of the Bolivian Altiplano and southernPeru. Posnanskytherium desaguaderoi (type species), P. inchasense, P. viscachanense, and P. pacis are the four speciesrecognized so far. In this contribution, we present the first remains of Posnanskytherium desaguaderoi (incomplete skull andfragmentary mandibles) from the Casira locality (Upper Member of the Tafna Formation, Pliocene), eastern Puna, Jujuy Province,Argentina, and provide an extended diagnosis of the genus and the type species. A new phylogenetic analysis recoversPosnanskytherium as monophyletic clade, with P. desaguaderoi as the sister taxon of P. inchasense and P. viscachanense. Thebody mass calculated for all Posnanskytherium species indicates that P. desaguaderoi has an intermediate body mass betweenthe highest values corresponding to P. viscachanense and P. inchasense and the lowest values to P. pacis. This finding fromthe eastern Argentinian Puna constitutes the northernmost record of a toxodontid in Argentina, the first appearance of Posnanskytheriumin the country, the southernmost record of the genus, and reinforces the paleofaunistic similarity with the BolivianAltiplano. Evidence shows that the genus Posnanskytherium had a wide distribution during the late Neogene, ranging fromsouthern Peru to northern Argentina, reaching a greater diversification in the Bolivian Altiplano during the Pliocene.