Interatherium interruptum Ameghino, 1894a

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, Zootaxa 4543 (2), pp. 195-220 : 202

Interatherium interruptum Ameghino, 1894a

Holotype. MACN-A 3445 ( Fig. 1 D ), left maxilla with the alveolus of dP1, and series dP2–3 and P4–M3.

Age and provenance of the type material. Santacrucian SALMA, early Miocene , Santa Cruz Province ( Argentina).

Original description ( Ameghino 1894a: 18). “ De la taille de 1’ I. supernum . Cette espèce se distingue facilement par la présence de la première prémolaire supérieure qui est placée contre la partie antérieure de la deuxième, et par la disparition complète de la canine. Il y a une longue barre qui sépare la première prémolaire de l'incisive externe; le bord de cette barre porte un sillon longitudinal profond qui suit la même direction de la série dentaire. Longueur des sept molaires supérieures, 25 mm ”.

English translation. With the same size as I. supernum . This species is easily distinguished by the presence of the first upper premolar that is placed against the anterior part of the second, and by the complete absence of the upper canine. There is a long diastema that separates the first premolar from the external incisor; the margin of this diastema shows a deep longitudinal groove that has the same direction as the dental series. Length of the seven upper molars, 25 mm.

Comments. Ameghino (1894a) did not illustrate this species. According to Ameghino’s catalogue and Mones (1986), the left maxilla MACN-A 3445 is the type specimen of the species. This material lacks the canine and, instead, exhibits a long diastema placed anteriorly to the alveolus of dP1 (L = 4.1 mm). It also shows the groove described by Ameghino, and the length of dP1–M3 is 24.8 mm. All of this coincides with Ameghino’s (1894a) description and, consequently, MACN-A 3445 is confirmed as the holotype of I. interruptum .

Figures

FIGURE 1. Interatherium rodens, holotype MLP 12-2826, right maxilla with alveolus of dP1 and complete dP2 and P3–M3, in occlusal view (A); reproduction of figure 26 (B) from Ameghino (1889, plate 15). Interatherium anguliferum, holotype MACN-A 3444, right maxilla with C and P2–M1, in occlusal view (C). Interatherium interruptum, holotype MACN-A 3445, left maxilla with the alveolus of dP1 and complete dP2–3 and P4–M3, in occlusal view (D). Interatherium dentatum, holotype MACN-A 9863, skull and mandible articulated, left lateral view (E). Scale bar = 10 mm.