Protypotherium attenuatum Ameghino, 1887b

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 : 482-483

Protypotherium attenuatum Ameghino, 1887b

Syntypes. MACN-A 524 ( Fig. 2 A ), left maxilla with P2–M3, and MACN-A 628 ( Figs. 2 B–C ), right fragmented mandible with alveoli of i1–3 and the c (broken)–m1 series.

Diagnosis ( Ameghino 1887b: 15). “ Tamaño considerablemente menor que el de la especie precedente [ Protypotherium praerutilum ]. Series dentarias superiores, más arqueadas. Ultima muela inferior sin vestigios del lóbulo tercero sobre el lado externo. Longitud de las cinco últimas muelas inferiores, 21 milímetros. Alto de la rama horizontal, debajo del m.1, 13 mm ”.

English translation. Considerably smaller in size than the preceding species [ Protypotherium praerutilum ]. Upper tooth row more arched. Last lower molar without external traces of the third lobe. Length of the last five lower cheek teeth, 21 millimetres. Height of the horizontal ramus below m1, 13 mm.

Comments. In 1889, Ameghino expanded the original description of the species by adding more details on the characteristics of upper and lower dentition, and illustrated a fragmented mandible and a maxillary fragment ( Ameghino 1889, plate 14: figs. 20–21) herein reproduced in Figures 2 D–F . The mandibular fragment ( Ameghino 1889, plate 14: fig. 20) matches the measurements (length of p3–m3 = 22 mm; height mandibular ramus below m1 = 12 mm) originally given by Ameghino (1887b), so this type specimen was in fact illustrated. According to Ameghino’s catalogue, MACN-A 524, a maxilla with P2–M3, is the type specimen. Despite this, Mones (1986) indicated as type “MLP (-)”, which means that the type could be housed at the MLP, but that it could also be lost.

MACN-A 524 ( Fig. 2 A ) matches the original description ( Ameghino 1887b) as it is smaller (length of P2–M3 = 23.53 mm) than the holotype of P. praerutilum (length of left P2–M3 = 29.83 mm), and its cheek teeth are arranged in a more arched position. In addition, it is coincident with figure 21 of the Atlas ( Ameghino 1889), except for the loss of its P1 and the fact that the illustration presents a shorter M1 and a central fossette on P2, but these differences could be associated to some mistakes made by the illustrator given that the remaining features as well as the specimen dimensions and pattern of breakage are the same. In turn, the mandibular fragment MACN-A 628 is broken at the level of m1 and has lost the remaining molars of the series, which should be present according to Ameghino’s (1887b) description, reason why we could not measure p3–m3 length and the height of the mandibular ramus; nevertheless, MACN-A 628 matches the figure 20 of the Atlas ( Ameghino 1889: plate 14). Given that MACN-A 524 is a left maxilla and MACN-A 628 is a right partial mandible, it was not possible to evaluate if both articulate with each other. Ameghino did not indicate that they belonged to the same individual (as he used to do when this was the case) and we consider them as representing two different individuals. Therefore, MACN-A 628 and MACN-A 524 are considered the syntypes of P. attenuatum .

On the other hand, there are nine very fragmented mandibular specimens in the MLP (MLP 12-1822, right m3, MLP 12-1823, left m1–2 and broken m3, MLP 12-1830, left m3 with broken talonid, MLP 12-1841, left m2–3, MLP 12-1842, left incomplete p3–m1, MLP 12-1843, right m2–3, MLP 12-1844, right alveolus of p4 and m1, MLP 12-1850, right alveolus of m1 and m2, and MLP 12-1851, left m3) labelled as paratypes of P. attenuatum . However, as it happened with P. praerutilum , we noticed the lack of correspondence between these labels and the Old Collections catalogue, where none of these specimens is highlighted as “ paratype ” of P. attenuatum , and no indication regarding their provenance and/or collector is provided. Besides, there is no original tag or indication that could confirm their status as paratypes or that they were collected in 1887 by C. Ameghino, or that Ameghino had these specimens with him when describing P. attenuatum . Therefore, they are rejected as paratypes of the species.

Chronological and geographical distribution of the type specimen. Santacrucian SALMA, Santa Cruz 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.