A new litoptern Cramaucheniinae species, Pternoconius bondi, sp. nov., from Colhuehuapian levels of the Sarmiento Formation in Bajada del Diablo (Chubut, Argentina) is described herein. The specimen belongs to an adult animal and preserves the anterior portion of the skull with the maxillary region, some fragments of nasal bones, a small portion of the left zygomatic process, and most of the upper dentition (i.e., left P2–M3, right C, and right P1–M3). It is compared with the Deseadan species ?Coniopternium primitivum Cifelli and Soria 1983 and Pternoconius polymorphoides Cifelli and Soria 1983, and also with the Colhuehuapian species Cramauchenia normalis Ameghino and Theosodon lydekkeri Ameghino. Although the hypocone and precingulum development, the paracone and metacone heights, and the connection between paraconule and protocone are singular features, the main characters that diagnose this new species are lack of a mesostyle pillar, soft labial bending of the ectoloph, absence of the metaconule in molars, and the smaller size with respect to other species of the genus. Comparative study leads us to recognize this specimen as a new species that increases the diversity of the Macraucheniidae in the early Miocene of Patagonia.