Interatherium supernum Ameghino, 1887b

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 : 200-201

Interatherium supernum Ameghino, 1887b

Holotype. Not located, probably lost.

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

Original description ( Ameghino 1887b: 15). “ Tamaño mayor que el de la precedente [ I. rodens ]. Longitud de las siete muelas inferiores, 29 mm. Muelas inferiores más anchas. m3 con el lóbulo tercero apenas aparente ”.

English translation. Larger in size than the previous species [ I. rodens ]. Length of the seven lower cheek teeth, 29 mm. Lower cheek teeth wider. m3 with the third lobe barely apparent.

Comments. Ameghino (1887b) founded and characterised this species based on a mandibular fragment with at least all of its cheek teeth, but he did not illustrate it. Later, Ameghino (1889, plate 15: figs. 17–19) notably expanded the original description based on fragmented mandibles and, mainly, a partial maxilla, all of them collected by C. Ameghino in Santa Cruz River in 1887 (Fernicola 2011).

In contrast to the original description, Ameghino’s catalogue states that the maxilla MACN-A 424 is “ tipo 1 ” (1 st type), an old and informal term used to refer to an holotype (C. Scioscia, pers. comm.), and that the partial mandibles MACN-A 357 (alveoli of right i1 and left i1 –dp1 with complete p2–m1 series), MACN-A 358 (alveoli of left i1 –dp1 and complete p2–3 series) and MACN-A 359 (broken left p2 and complete p3–m2 series) are “ tipo 2 ”, an informal and antique expression used to refer to a paratype (C. Scioscia, pers. comm.).

Within the Ameghino Collection, MACN-A 424, MACN-A 357 and MACN-A 540 (right fragmented mandible with dp2–m1) correspond to figures 17, 18 and 19, respectively, of Ameghino’s Atlas (1889: plate 15). Nevertheless, none of these mandibular fragments is the holotype of the species, because they do not, either alone or combined, recreate the original dp1–p2–m3 series. Besides, as they do not present any evidence of recent break, it is inferred that they have not lost any dental piece through time in the collection. In addition, these materials do not present wide lower molariforms as originally described by Ameghino (1887b). Regarding the maxilla MACN- A 424, it is also discarded as type material due to the fact that Ameghino (1887b) only described lower dentition of I. supernum . As a matter of fact, if he had had the maxilla at hand, he would have compared and contrasted I. supernum and I. rodens not only based on lower teeth but also on upper teeth, which he did in detail in 1889, when he even recognised that the lower dentition of I supernum did not present anything in particular except its size and more continuous anterior dentition.

On the other hand, Mones (1986) indicated MLP 12-1846 (right mandibular fragment with p4–m3), MLP 12- 1878 (incomplete left maxilla with P3–M2), MLP 12-1879 (right maxilla with broken P3, P4–M2, and broken M3), MLP 12-1885 (left mandibular fragment with p3–m1), MLP 12-1886 (right mandibular fragment with dp4–m2), MLP 1887 (right mandibular fragment with p3–m1) and MLP 12-1921 (left mandibular fragment with p4–m2 and broken m3) as the type specimens of I. supernum . In the collection of MLP, all these specimens are labelled as paratypes of I. supernum . However, MLP 12-1878 and MLP 12-1879 are discarded as type materials because they are maxillae. The same conclusion is inferred for the fragmented mandibles, because they do not exhibit the tooth row mentioned in the original diagnosis ( Ameghino 1887b) and there is no evidence of any recent break. In the case of MLP 12-1846, which is the only specimen with complete m3, it does not exhibit the characteristics originally mentioned by Ameghino (1887b). It is worth mentioning that when comparing the labels of these specimens (indicating them as paratypes) with the Old Collections catalogue, which was written 30 years before the labelling (M. Reguero, pers. comm.), we noticed that there are many inconsistencies that make us question the veracity of the labelled information. On the one hand, none of the materials labelled as “ paratype ” is indicated as such in the Old Collections catalogue; in fact, the term is a modern expression that was never used by Florentino Ameghino. On the other hand, in contrast to the labels, there is no information in Old Collections catalogue concerning the collector and/or provenance of these specimens. Due to all of these facts and that there is no original tag that validates their status as paratypes or even confirms that any of these materials was actually collected by Carlos Ameghino in 1887 and used by Florentino Ameghino to describe I. supernum , they are all rejected as the paratypes of the species.

In summary, the holotype of I. supernum has not been located either in MACN-A and MLP collections or in any other collection revised by mean of photographs (e.g., AMNH, FMNH and YPM).