Icochilus ulter Ameghino, 1899 Holotype. MACN-A 11601 (Figs. 6 H–I), right mandibular fragment with p3–m3 and left mandibular fragment with p4–m1 series. Age and provenance of the type material. Astrapothericulan beds (presumably the Pinturas Formation), early Miocene, Santa Cruz Province (Argentina). Original description (Ameghino 1899: 5). “ De la talla del Icochilus extensus, pero de rama mandibular más alta (20 milímetros debajo de la quinta muela) ”. English translation. With the size of Icochilus extensus, but with a highest mandibular ramus (20 millimetres below the fifth molar). Comments. Ameghino (1899) briefly described this species without illustrating it, but he did not mention it in his catalogue. There is no specimen indicated as type of Ic. ulter in the Ameghino Collection. Despite this, Mones (1986) indicated, but with doubts, “MACN-A 10601?” as type specimen; however, this specimen is also indicated by the author as the type of the isotemnid Eochalicotherium crassidens. MACN-A 10601 is in fact a lot constituted by three mandibular fragments—with one tooth each—that belong to the latter species; consequently, it is discarded as the holotype of Ic. ulter. On the other hand, the lot MACN-A 11601, which is composed of two mandibular fragments of the same individual, with right p3–m3 and left p4–m1, is the only material assigned by F. Ameghino to Ic. ulter within the Ameghino Collection. The right fragment matches the only measurement (length of the mandibular ramus below m1 = 20 mm) given by Ameghino (1899). It is worth mentioning that there are two pieces of paper inside the container with Ameghino’s handwriting: one that reproduces the original description of the species and another with the name “ Icochilus ulter ”. In the latter, it is also written “10601” but with someone else’s handwriting (probably from M. Soria; A. Kramarz, pers. comm.), and the first ‘0’ was crossed out and replaced by ‘1’; it is very likely that this mistake led Mones to mention “MACN-A 10601?” as the type of the species. As a result, MACN-A 11601 is identified as the holotype of Ic. ulter.

Published as part of Fernández, Mercedes, Fernicola, Juan Carlos & Cerdeño, Esperanza, 2019, On the type materials of the genera Interatherium Ameghino, 1887 and Icochilus Ameghino, 1889 (Interatheriidae, Notoungulata, Mammalia) from early Miocene of the Santa Cruz Province, Argentina, pp. 195-220 in Zootaxa 4543 (2) on page 216, DOI: 10.11646/zootaxa.4543.2.2, http://zenodo.org/record/2617757