Icochilus anomalus 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 : 211-212

Icochilus anomalus Ameghino, 1894a

Holotype. MACN-A 3634 ( Fig. 5 I ), mandibular right fragment with c and p2–3, currently missing.

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

Original description ( Ameghino 1894a: 16). “ De la même taille que l’ Icochilus extensus . Cette espèce se distingue facilement par l'atrophie et la disparition de plusieurs dents. L'incisive inférieure externe est très petite. La canine inférieure est extrêmement petite, et isolée en avant et en arrière par des diastèmes assez longs, tandis que dans presque toutes les autres espèces du même genre cette dent est au contraire bien développée et couchée en avant sur les incisives, dont elle en a la forme. La première prémolaire inférieure a complètement disparu. La deuxième prémolaire inférieure est bien développée et avec deux sillons perpendiculaires opposés, l'un interne et l'autre externe ”.

English translation. With the same size as Icochilus extensus . This species is easily distinguished by the atrophy and disappearance of several teeth. The external lower incisor is very small. The lower canine is extremely small and is anteriorly and posteriorly isolated by rather long diastemata, whereas in almost all the other species of the genus this tooth is instead, well developed and leaned on the incisors. The first lower premolar is absent. The second lower premolar is well developed and exhibits two opposite, internal and external, perpendicular grooves.

Comments. Ameghino (1894a) described this species, but did not illustrate any specimen of it. Ameghino’s catalogue and Mones (1986) indicate the mandibular fragment MACN-A 3634 as the type specimen of the species. This is the only material assigned to this species in Ameghino’s catalogue, but unfortunately, it could not be found in the Ameghino Collection. Nevertheless, when studying Scott’s photographic catalogue published by Vizcaíno et al. (2017), it was possible to identify the photograph No. 309 ( Fig. 5 I ) as the fragmented mandible assigned to Ic. anomalus by Ameghino (1894a). That specimen matches the original description, because it exhibits a reduced lower canine, diastemata anterior and posterior to this tooth, and the absence of dp1. Taking into consideration that MACN-A 3634 was the only specimen assigned to this species, it is highly probable that the photograph No. 309 corresponds to the currently missing specimen. Therefore, if this was the case, it should be considered the holotype of Ic. anomalus , but unfortunately it has not been located.

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.