Icochilus multidentatus 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 : 213-215

Icochilus multidentatus Ameghino, 1894a

Lectotype (this contribution). MACN-A 3637 ( Fig. 6 A ), right maxilla with alveolus of an extra tooth and C, and complete series dP1–P2–M3.

Paralectotypes (this contribution). MACN-A 3638 ( Figs. 6 B–C), right mandibular fragment with dp1–4 and m1–3 .

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

Original description ( Ameghino 1894a: 17). “ De taille assez petite; elle se distingue pour avoir huit molaires en haut et en bas, de chaque côté, dont les cinq antérieures sont des prémolaires. Â la mâchoire supérieure, la canine et les deux premières prémolaires sont très petites et en série continue avec les autres dents. A la mâchoire inférieure, les deux premières prémolaires ont la forme de petites canines et la deuxième est séparée de la troisième par un petit diastème. Les deux premières prémolaires inférieures et la canine se suivent sans diastème. Les huit molaires supérieures occupent une longueur de 28 mm ”.

English translation. Quite small; it is distinguished in having eight upper and lower cheek teeth, of which the anterior five are premolars. In the maxilla, the canine and the first two premolars are very small and placed in a continuous series with the other cheek teeth. In the mandible, the first two premolars look like small canines and the second is separated from the third by a small diastema. The first two lower premolars and the canine follow each other without diastemata. The eight upper cheek teeth occupy a length of 28 mm.

Comments. Ameghino (1894a) did not figure any material of this species. According to Ameghino’s catalogue and Mones (1986), MACN-A 3637, a right maxilla, and MACN-A 3638, an incomplete right mandibular ramus, are the type specimens of the species. MACN-A 3637 matches the original description because it exhibits a broken alveolus that indicates the presence of an extra tooth, which is discarded as I3 because there is no trace of the premaxilla-maxilla suture. Regarding lower dentition, MACN-A 3638 also matches the original diagnosis as it presents what can be considered at first sight an extra alveolus, as well as c and the first premolar (according to Ameghino) without separation, whereas there is a diastema between the second and third premolar of the tooth row. Consequently, both materials are confirmed as types, but due to the fact that they belong to two different individuals in two different ontogenetic stages—MACN-A 3637 presents all permanent dentition, whereas MACN-A 3638 exhibits deciduous premolars (dp2–4)—both are considered as syntypes of Ic. multidentatus . In addition, the comparison with other specimens of Icochilus allows us to recognize the extra lower alveolus of MACN-A 3638 as corresponding to i3; in consequence, we select this specimen as the lectotype of Ic. multidentatus as it undoubtedly exhibits the main diagnostic characteristic—extra tooth—of the species, and then MACN-A 3638 becomes the paralectotype ( ICZN 2000: Art. 73.2.2).

Figures

FIGURE 6. Icochilus multidentatus, lectotype MACN-A 3637, right maxilla with alveolus of extra tooth and C and dP1–M3, in occlusal view (A); paralectotype MACN-A 3638, right mandibular fragment with dp1–4 and m1–3, in oclusal (B) and lingual (C) views. Icochilus hegetotheroides, holotype MACN-A 9855, incomplete skull, anterior view of the premaxilla with labial view of both I1 (D) and right lateral view (E); holotype MACN-A 9856, incomplete mandible, in occlusal (F) and left lateral (G) views. Icochilus ulter, holotype MACN-A 11601, right mandibular fragment with p3–m3, in oclusal (H) and labial (I) views. Scale bar = 10 mm.