Species: rionegrina BONAPARTE, 1990
Etymology: In reference to Rio Negro Province, Argentina.

Holotype: MACN-RN 163

Locality: Estancia Los Alamitos, west slope of Cerro Cuadrado, Arroyo Verde, Rio Negro Province, Patagonia, Argentina.

Horizon: Top of the Cerrito del Mamifero, lower section of the Los Alamitos Formation.

Biostratigraphy:

Age: Alamitan Provincial Age, Allenian Tetrapoda Assemblage, Late Campanian-Early Maastrichtian Stage, Senonian Subepoch, Gulf Epoch, Late Cretaceous.

Material: An almost complete crown of an upper molar.

Hypodigm: MACN-RN 229: A complete crown of an upper molar.

Referred material:

BONAPARTE, 2002

MACN-RN 1032: A left upper molar.

MACN-RN 1033: A right upper molar.