Protypotherium obstructum Ameghino 1888

Fernández, Mercedes, Fernicola, Juan Carlos, Cerdeño, Esperanza & Reguero, Marcelo A., 2018, Identification of type materials of the species of Protypotherium Ameghino, 1885 and Patriarchus Ameghino, 1889 (Notoungulata: Interatheriidae) erected by Florentino Ameghino, Zootaxa 4387 (3), pp. 473-498 : 483

Protypotherium obstructum Ameghino 1888

Holotype. MACN-A 1677 ( Fig. 2 G ), lower premolar.

Diagnosis ( Ameghino 1888: 14). “ Esta especie está representada por un solo premolar inferior, pero de una forma tan distinta de los mismos dientes de las otras especies que indica claramente no puede proceder de ninguna de las ya conocidas. Es el premolar tercero o cuarto de la mandíbula inferior, y difiere de los mismos dientes de las demás especies, por el surco perpendicular externo menos profundo, y por no presentar vestigios del surco interno opuesto. La cara perpendicular interna es así casi plana, con una muy pequeña elevación perpendicular en el medio. Largo de la corona, 0.0045. Es esta la especie más moderna del género ”.

English translation. This species is represented by a single lower premolar so different from the same teeth of the other known species that clearly indicates that it does not belong to any of them. It is the third or fourth lower premolar, and differs from the same teeth of the other species by the shallower external perpendicular groove and the lack of the opposite internal groove. Thus, the internal perpendicular face is almost flat, with a very small perpendicular elevation in the middle. Length of the tooth crown, 0.0045 m. This is the most modern species of the genus.

Comments. In 1889, Ameghino expanded the original diagnosis of the species by describing with more detail the lower premolar collected at Monte Hermoso (Buenos Aires Province) by his brother Carlos, which was indicated by Florentino as the only assignable material. Florentino Ameghino also illustrated this tooth ( Ameghino 1889: plate 14, fig. 14), which is herein reproduced in Figure 2 H . No material is indicated as the type in Ameghino´s catalogue, but Mones (1986) recognised MACN-A 1677 as such. This specimen is a lower premolar that completely matches the original description (e.g., length equals 4.88 mm; its morphology differs from all the remaining species of the genus as the labial sulcus is extremely shallow, the lingual face is completely flat and lacks any sulcus) and posterior illustration ( Ameghino 1889). Therefore, MACN-A 1677 is herein confirmed as the holotype of P. obstructum .

Chronological and geographical distribution of the type specimen. Montehermosan SALMA ( Ameghino 1889), Buenos Aires Province.

Figures

FIGURE 2. Protypotherium attenuatum, syntype MACN-A 524, left maxilla with P2–M3 but lacking P1, in occlusal view (A); syntype MACN-A 628, right fragmented mandible with alveoli of i1–3 and c (broken)–m1 but lacking m2–3, in labial (B) and occlusal (C) views; reproductions of figures 21 (D), 20 (E) and 20a (F) from Ameghino (1889, plate 14). Protypotherium obstructum, holotype MACN-A 1677, lower premolar in labial, oclusal and lingual views (G); reproduction of figure 19 (H) from Ameghino (1889, plate 15). Protypotherium claudum, holotype MACN-A 551, right mandibular fragment with alveolus of p2 andp3–m2, in labial (I) and occlusal (J)views; reproductions of figures 22 (K) and 22a (L) from Ameghino (1889, plate 14). Protypotherium globosum, holotype MACN-A 4049, skull, in ventral (M) and dorsal (N) views. Protypotherium convexidens, holotype MACN-A 4054, right maxillary fragment with P3–M2 (broken), in occlusal view (O). Protypotherium diversidens, holotype MACN-A 4052, right maxillary fragment with alveolus of P1 and P2–M3, in occlusal view (P). Protypotheriumcompressidens, holotype MACN-A 4029, left maxillaryfragment withP3–M3, in occlusal view (Q); holotype MACN-A 4030, left mandibular fragment with p4 (talonid)–m3, in occlusal view (R). Protypotherium lineare, holotype MACN-A4039, right mandibular fragment with alveolus of p1 and p2–m1, in occlusal view (S); holotype MACN-A 4038, left mandibular fragment with p3–m2, in occlusal view (T). Scale bar = 10 mm.