First Skull and Associated Postcranial Bones of Macraucheniidae (Mammalia, Litopterna) from the Deseadan Salma (Late Oligocene) of Cabeza Blanca (Chubut, Argentina)

The first skull associated with postcranial elements of Macraucheniidae (Litopterna) from the Sarmiento Formation in Cabeza Blanca (Chubut, Argentina) are described herein. The material consists of a nearly complete skull, nearly complete right humerus, left metacarpal IV, and three phalanges (proximal, intermediate, and distal of the same digit) of the same individual. It is compared with the Santacrucian genus Theosodon Ameghino, the Colhuehuapian Cramauchenia Ameghino, and the Deseadan species Coniopternium andinum and C. primitivum Soria and Hoffstetter. The comparative study leads us to recognize this specimen as Cramauchenia normalis. The presence of this species in Cabeza Blanca increases its biochronological distribution to Deseadan South American Land Mammal Age (SALMA) (late Oligocene).