Icochilus truncus 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 : 213

Icochilus truncus Ameghino, 1894a

Holotype. MACN-A 3635 ( Figs. 5 J–K), right fragmented mandible with alveoli of i1 –dp1 and the series p2–m1.

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

Original description ( Ameghino 1894a: 16). “ A peu près de la même taille que l’ I. extensus . Elle se distingue par la présence de la première prémolaire inférieure très petite, et par l'absence de la canine inférieure. A la place de la canine il y a un diastème assez étendu qui sépare l'incisive externe de la première prémolaire ”.

English translation. Size almost the same as Ic. extensus . It is distinguished by the presence of a very small first lower premolar, and by the absence of the lower canine. In the place of the lower canine there is a rather extensive diastema that separates the external incisor from the first premolar.

Comments. Ameghino (1894a) did not add any illustration to the brief description of I. truncus . According to Ameghino’s catalogue and Mones (1986), MACN-A 3635, a broken symphysis with a fragmented right mandibular ramus, is the type material of the species. This specimen has a small alveolus of dp1 and a diastema between i3 and dp1, whose length (2.2 mm) falls within the range (1 to 3 mm) that Ameghino provided for any gap between adjacent teeth ( Ameghino 1894a: 15–18). These characteristics are consistent with Ameghino’s (1894a) description and, consequently, MACN-A 3635 is confirmed as the holotype of Ic. truncus .

Figures

FIGURE 5. Icochilus lamellosus, holotype MACN-A 3631, incomplete skull, in ventral view (A). Icochilus trilineatus, MACN-A 3633, left M2, in occlusal view (B); MACN-A 3651 to MACN-A 3657 in occlusal view (C–H): left P4 or M1/2 (C), left P4 or M1/2 (D), left M3 (E), right P4 or M1/2 (F), right M3 (G), right m3 (H). Icochilus anomalus, detail of photograph of the holotype MACN-A 3634 from Scott’s catalogue (I). Icochilus truncus, holotype MACN-A 3635, right fragmented mandible with alveoli of i1–dp1 and complete p2–m1, in occlusal (J) and lateral (K) views. Icochilus crassiramis, holotype MACN-A 3636, right mandibular fragment with i2–m3, in occlusal (L) and lateral (M) views. Scale bar = 10 mm.