Updated record of Proterotheriidae (Litopterna, Mammalia) from the late Neogene of northwestern Argentina

Abstract

We describe several proterotheriid remains from the Andalhuala and the Corral Quemado formations (Villavil-Quillay and Santa María basins, Catamarca Province) and the Andalhuala Formation (Santa María Basin at Encalilla, Tucumán Province), Argentina. Neobrachytherium intermedium distinguishes from N. morenoi by the presence of lophoid metaconules in upper molars and astragalus with fusiform attachment for the tibioastragalar ligament, while N. morenoi presents bunoid metaconules and astragalus with ectal facet slightly projected laterally without attachment for the tibioastragalar ligament. ?Proterotherium simplicidens is considered junior synonym of N. intermedium. N. intermedium is circumscribed to levels ca. 6.02 Ma in the Santa María Basin (extendable to ca. 6.88 Ma), to ca. 3.66 Ma in Puerta de Corral Quemado. N. morenoi is restricted to levels above ca. 6.02 to below ca. 4.85 Ma in the Santa María Basin. While other species of Neobrachytherium (i.e. N. ullumense and N. ameghinoi) are distributed in Argentina and Uruguay, N. intermedium and N. morenoi only have records in the late Neogene of northwestern Argentina. These distributions align with earlier hypotheses regarding a regional ecological distinction between the western and eastern regions in the northern half of Argentina during the late Neogene while also fitting the paleophytogeographic provinces (Neotropical and Proto-Spinal).