Pliocene mammals from Inchasi, Bolivia: The endemic fauna just before the Great American Interchange

Abstract

A new, high-elevation (3200 m) mammalian local fauna is described from Communidad Inchasi, ca. 50 km SE of Potosi, Bolivia. The fauna consists of 4 orders (Edentata, Rodentia, †Litopterna and †Notoungulata), 9 families, 10 genera, and at least 11 species. Of these, one new genus and two new species of notoungulates are described. This fauna contains two genera endemic to the Bolivian altiplano, †Posnanskytherium and †Hypsitherium n. gen., whereas the remaining eight genera (†Glossotheridium, †Proscelidodon, †Plaina, †Plohophorus, †Paraglyptodon, †Chapalmatherium, †Caviodon, and † Promacrauchenia) are referable to previously described genera from the Pliocene ofArgentina. The biochronology of the Inchasi mammals indicates either a: (1) Montehermosan/ Chapadmalalan (undifferentiated) age because the included taxa are either restricted to the Montehermosan, Chapadmalalan, or span both mammal ages; or (2) Chapadmalalan age based on recent biostratigraphic redefinitions from classic localities in Argentina. Previous magneto- and biostratigraphic data indicate that the Inchasi beds and their contained mammalian fauna are middle Pliocene with an age range of between 3.3 and 4.0 myr ago. The Inchasi local fauna lacks any immigrant taxa and thus represents an endemic fauna that occurred about 1 myr before the beginning of the Great American Interchange.