A new combination: Cochilius pendens Ameghino, 1902 and Cochilius columnifer Ameghino, 1902Ameghino erected C. pendens (1902:7677) and C. columnifer (1902:77) without illustrating them. The former was based on a mandibular symphysis with one tooth, and the latter on a right mandibular fragment with three teeth and an isolated tooth. No specimen is indicated as the type of these species in the MACN-A, but Mones (1986:153) listed MACN-A 52-280 (symphysis with left p3; Fig. 7A; Table S3, Supplemental Data 3) as the type of C. pendens and MACN-A 52282 (right mandibular fragment with p4m2;Fig. 7B D; Table S3, Supplemental Data 3) and MACN-A 52-283 (left m2; Fig. 7E; Table S3, Supplemental Data 3) as that of C. columnifer. These specimens match the original descriptions and measurements provided by Ameghino (1902), which is the reason why MACN-A 52-280 is confirmed here as the holotype of C. pendens, and MACN-A 52-282 and MACN-A 52-283 (both belonging to the same individual) as the holotype of C. columnifer. These holotypes are harmonious and similar in morphology (e.g., the talonid and trigonid of the lower premolars present the same labio-lingual expansion, but the mesio-distal length of the trigonid is larger than that of the talonid) and size, which allows us to infer that they belong to the same taxonomic entity. Despite the fact that C. pendens was described first in the paper, C. columnifer is selected here as the senior synonym because its holotype is a more complete specimen, following the criteria of the first reviewers choice (IZCN, 2000:art. 23). On the other hand, MACN-A 52-280, MACN-A 52-282, and MACN-A 52-283 present unmolarized lower premolars, in contrast to the species recognized here in the genus Cochilius, but instead diagnostic of Protypotherium. The talonid of the lower premolars is much less developed than the trigonid and the m12 of MACN-A 52-282 and MACN-A 52-283 are morphologically very similar to each other, with their talonid longer than the trigonid, both being sub-triangular, and the ectoflexid much transversally deeper than the entoflexid; all these characteristics do not match the species of Cochilius, but Protypotherium. Therefore, MACN-A 52-280, MACN-A 52-282, and MACN-A 52-283 are here assigned to Protypotherium, under the new combination Protypotherium columnifer. It is worth mentioning that P. columnifer is similar to P. sinclairi Kramarz et al., 2015 from the Cerro Bandera Fm. (early Miocene; Colhuehuapian), sharing the equal width of the talonid and the trigonid on the premolars. The taxonomic revision of Protypotherium is still pending, as already highlighted by other authors (e.g., Cassini et al., 2012; Kay et al., 2012; Vera et al., 2017b; Fernndez et al., 2019b), and this is why we cannot conclude anything further about this new combination.