Protypotherium lineare Ameghino, 1894a

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 : 486-487

Protypotherium lineare Ameghino, 1894a

Holotype. MACN-A 4038 ( Fig. 2 S ), right mandibular fragment with alveolus of p1, and p2–m1, and MACN-A 4039 ( Fig. 2 T ), left mandibular fragment with p3–m2 series, both specimens of the same individual.

Diagnosis ( Ameghino 1894a: 13–14). “ Cette espèce, par la taille se rapproche du P. australe , mais s'en distingue facilement par les deux dernières prémolaires inférieures qui, au lieu d'être implantées obliquement comme dans les autres espèces, sont placées avec leur grand axe dans la même direction de la série dentaire. A conséquence de cette disposition, le sillon vertical, au lieu d'être placé en arrière il est en dehors; ce sillon est très profond, et le lobule postérieur externe de chaque prémolaire est bien développé, formant une colonne étroite mais élevée. Longueur des sept molaires inférieures 38 mm. Hauteur de la mandibule: en dessous de la 2 p. 13 mm.; en dessous de la partie antérieure de là 3 m. 20 mm ”.

English translation. This species is close in size to Protypotherium australe , but it is easily distinguished from it by the last two lower premolars that, instead of being obliquely implanted as in the other species, are placed with their major axis in the same direction of the tooth row. Due to this position, the vertical groove is placed outside instead of backwards; this groove is very deep, and the posterior lobe of each premolar is externally well developed, forming a narrow and high column. Length of the seven lower teeth: 38 mm. Height of the mandible: below p2, 13 mm; below the anterior region of m3, 20 mm.

Comments. Ameghino (1894a) did not add any illustration to the description of P. lineare . In the Ameghino Collection, this species is represented by eight materials. According to Ameghino’s catalogue and to Mones (1986), two mandibular fragments, MACN-A 4038 and MACN-A 4039, are the type material of the species; following Ameghino’s catalogue, both belong to the same individual. Due to the presence of recent breaks, it is inferred that m3 got lost. Nevertheless, the measurements available to be taken (height of the mandibular ramus below p2 = 13.7 mm; below the mesial region the alveolus of left m3 = 19.8 mm) match those provided by Ameghino (1894a). Regarding the remaining six specimens assigned to P. lineare , five of them are too incomplete mandibular fragments, smaller than MACN-A 4038 and MACN-A 4039, and those with their p2 and/or m3 do not match the original measurements regarding the height of the mandible; then, they are all discarded as type specimens. The sixth specimen, MACN-A 4040 (partial right mandible with c, alveoli of p1–3 and complete p4–m3), is closer in size to the original mandibular fragment, but it is still smaller (height of the mandibular ramus below p2 = 12.48 mm; below m3 = 17.36 mm), and lacks its p3 (the alveolus is filled with sediment), which also allows discarding it as the type specimen because Ameghino specifically described p3–4. Consequently, the individual MACN-A 4038 plus MACN-A 4039 is confirmed as the holotype of P. lineare .

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.