Icochilus hegetotheroides 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 : 215-216

Icochilus hegetotheroides Ameghino, 1894a

Holotype. MACN-A 9855 ( Figs. 6 D–E), anterior cranial fragment, and MACN-A 9856 ( Figs. 6 F–G), an incomplete mandible, both of the same individual.

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

Original description ( Ameghino 1894a: 17). “ Cette espèce se distingue par le grand développement de la paire d'incisives internes supérieures (i. 1), comparables sous ce rapport à celles du genre Hegetotherium . Ces

incisives sont convexes en avant, concaves en arrière, et avec la surface de la couronne en arc de cercle. La deuxième incisive est petite, et la troisième incisive ainsi que la canine sont atrophiées. La partie antérieure du crâne est très raccourcie et proportionnellement très large. La couronne de chacune des incisives internes a 5 mm. 5 de diamètre transverse en ligne droite. Le palais au niveau des canines a 13 mm. de largeur, et la distance du bord antérieur de la p. 1 au coin interne de l'i. 1 est de seulement 46 mm ”.

English translation. This species is distinguished by the great development of the internal upper incisors (I1), similar in this aspect to those of the genus Hegetotherium . These incisors are labially convex, lingually concave, and with an arched surface of the crown. The second incisor is small, and the third incisor and the canine are atrophied. The anterior part of the skull is very short and proportionally very broad. The crown of each internal incisor measures 5 mm. 5 of transverse diameter in a straight line. The palate is 13 mm wide at the level of the canines, and the distance from the anterior part of P1 to the internal part of I1 is only 46 mm.

Comments. Ameghino (1894a) did not illustrate any specimen of this species. According to Ameghino’s catalogue and Mones (1986), MACN-A 9855 (anterior portion of a skull) and MACN-A 9856 (incomplete mandible), which belong to the same individual, are the type specimens of the species. The measurements of MACN-A 9855 (MDL of I1 = 5.5–5.7 mm; width of the palate at the C level = 13.2 mm; length of I1 –dP1 = 16.3 mm) match approximately those provided by Ameghino (1894a). Therefore, MACN-A 9855 and MACN-A 9856 are confirmed as the holotype of Ic. hegetotheroides .

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.