Patriarchus diastematus Ameghino, 1891 Holotype. MACN-A 4044 (Fig. 3 Q), two maxillae with alveoli of left and right C–P1, right P2–M3 and left P2– M2. Diagnosis (Ameghino 1891: 293). “ Del mismo tamaño que la especie precedente [Patriarchus rectus], o apenas algo mayor, de la cual se distingue por el P1 pequeño, cilíndrico y separado del que sigue por un pequeño diastema. Series dentarias superiores un poco más arqueadas. Longitud del P2 al M3, 29 milímetros. Ancho del paladar entre los M3, 18 milímetros; ancho entre los M1, 20,5 milímetros; ancho entre los P2, 13 milímetros ”. English translation. Same size as the preceding species [Patriarchus rectus] or slightly larger, from which it is distinguished by its small, cylindrical P1, separated from the following premolar by a small diastema. Upper tooth row a little more arched. Length from P2 to M3, 29 millimetres. Width of the palate between M3s, 18 millimetres; between M1s, 20.5 millimetres; between P2s, 13 millimetres. Comments. Ameghino (1889) described this species without providing any illustration of it. In the Ameghino Collection, Pa. diastematus is represented just by one specimen. According to Ameghino’s catalogue and to Mones (1986), maxilla MACN-A 4044 is the type material. This specimen matches the original description because it presents a slightly larger size (length of P2–M3 = 28.1 mm) to that of the holotype of Pa. rectus (length of P2–M3 = 27.5 mm) and, according to its alveolus, P1 is small and cylindrical and is separated from P2 by a small diastema (~ 1.4 mm). Besides, all the measurements (length of P2–M3 = 28.88 mm; width of the palate between both M3 = 19 mm; width of the palate between both M1 = 20.8 mm; width of the palate between both P2 = 13.7 mm) coincide with those provided by Ameghino (1891). As a result, MACN-A 4044 is confirmed as the holotype of Pa. diastematus. Chronological and geographical distribution of the type specimen. Santacrucian SALMA, Santa Cruz Province.

Published as part of Fernández, Mercedes, Fernicola, Juan Carlos, Cerdeño, Esperanza & Reguero, Marcelo A., 2018, Identification of type materials of the species of Protypotherium Ameghino, 1885 and Patriarchus Ameghino, 1889 (Notoungulata: Interatheriidae) erected by Florentino Ameghino, pp. 473-498 in Zootaxa 4387 (3) on page 492, DOI: 10.11646/zootaxa.4387.3.4, http://zenodo.org/record/1187697