Icochilus lamellosus 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 : 210

Icochilus lamellosus Ameghino, 1894a

Holotype. MACN-A 3631 ( Fig. 5 A ), incomplete skull with complete dentition.

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

Original description ( Ameghino 1894a: 15–16). “ Espèce de petite taille. La canine supérieure est bien développée, de la même grandeur et à peu près de la même forme que l'incisive externe, étant séparées l'une de l'autre par un petit diastème; ces deux dents sont comprimées latéralement et ont la forme de lames tranchantes. L'incisive externe ou troisième, est séparée de la deuxième par un diastème assez long; un autre diastème un peu plus long sépare la première prémolaire de la canine. La p 1 est placée contre la p 2 et porte un sillon vertical à son angle antérieur externe. Longueur du bord antérieur de l'i 1 au bord postérieur de la m 3, 37 mm ”.

English translation. Species of small size. The upper canine is well developed, of the same size and nearly the same form as the external incisor, being separated from each other by a small diastema; these two teeth are laterally compressed and have the appearance of cutting blades. The external incisor, or third, is separated from the second by a rather long diastema; another slightly longer diastema separates the first premolar from the canine. The P1 is placed against P2 and has a vertical groove at its antero-external angle. Length from the anterior edge of I1 to the posterior border of m3, 37 mm.

Comments. Ameghino (1894a) did not add any illustration to the description of this species. According to Ameghino’s catalogue and Mones (1986), the incomplete skull MACN-A 3631 is the type specimen. MACN-A 3631 exhibits a well-developed upper canine that is subequal to I3 —being both teeth laterally compressed—, and the diastemata I2–3, I3 –C and C–dP1 mentioned by Ameghino (1894a). Even though the author did not indicate the dimensions of these discontinuities, he established relative differences in size, which resemble those obtained in the material (length of diastema I2–3 = left, 0.9 mm and right, 1.4 mm; length diastema I3 –C: left, 0.4 mm and right, 0.8 mm; length of diastema C–dP1: left, 2.6 mm and right, 2.2 mm). The length of I1 –M3 series (38 mm) also matches the value provided by Ameghino (1894a). Therefore, MACN-A 3631 is confirmed as the holotype of Ic. lamellosus .

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.