Icochilus crassiramis 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 crassiramis Ameghino, 1894a

Holotype. MACN-A 3636 ( Figs. 5 L–M), right mandibular fragment with i2 –m3.

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

Original description ( Ameghino 1894a: 16–17). “ De la même taille que 1’ I. extensus . Cette espèce se distingue très bien par la première prémolaire inférieure qui a la forme d'une canine bien développée, étant isolée en avant et en arrière par des diastèmes assez longs. La canine inférieure a la forme d'une incisive, étant couchée en avant sur l'incisive externe. La deuxième prémolaire inférieure est elliptique, sans sillon perpendiculaire interne; de celui du côté externe on en voit à peine des traces ”.

English translation. Same size as Ic. extensus . This species is very well distinguished by its first lower premolar that has the morphology of a well-developed canine, being anteriorly and posteriorly isolated by rather long diastemata. The lower canine is incisor-shaped, anteriorly leaned on the external incisor. The second lower premolar is elliptical, without internal perpendicular groove; no trace of external groove is visible.

Comments. Ameghino (1894a) did not illustrate any specimen of this species. According to Ameghino’s catalogue and Mones (1986), MACN-A 3636, a right mandibular ramus, is the type specimen. This material matches the original description ( Ameghino 1894a) because it exhibits a canine-like dp1 separated by anterior (L = 1.5 mm) and posterior (L = 1.2 mm) diastemata, and an elliptical p2 with very shallow ectoflexid and entoflexid. These characteristics match Ameghino’s (1894a) description and, as a result, MACN-A 3636 is confirmed as the holotype of Ic. crassiramis .

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.