Abstract

We report herein a new genus and species of Pyrotheria, Berracotherium koimeterion, from the Quebrada de Los Colorados Formation (middle Eocene-early Oligocene), Salta Province (Argentina). Up to this contribution, pyrotheres had only been known from northwestern Argentina by a single fragmentary tusk referred to Propyrotherium from the Geste Formation (late Eocene), Catamarca Province. This new taxon is based on a right mandibular fragment with the roots of dp4–m1 and m2 in eruption, and it can be differentiated from other pyrotheres as follows: horizontal mandibular ramus high and robust; mandibular symphysis large that extends posteriorly to reach m1; lower cheek teeth longer than wide; m2 bilophodont; mesial and distal lophids completely separated at the labial and lingual ends; both lophids transverse, parallel, nearly straight, and low; crenulations on lophids; the cristid obliqua that connects mesial and labial lophids is conspicuous, almost perpendicular to both lophids, and it is labially placed; and well-expanded distal cingulum that forms a third lobe. A cladistic analysis was performed that recovers Berracotherium gen. nov. as a member of Pyrotheriidae and includes it within an unresolved clade with Griphodon, Propyrotherium, Baguatherium, and Pyrotherium. Berracotherium koimeterion gen. et sp. nov. increases the known diversity of Pyrotheria at both regional and global scales, as well as its geographic and stratigraphic distribution.