Protypotherium antiquum Ameghino, 1885

Fernández, Mercedes, Fernicola, Juan C. & Cerdeño, Esperanza, 2023, Systematic revision of the species of Protypotherium (Notoungulata: Interatheriidae) from the Santa Cruz Formation (Early-Middle Miocene), Argentinian Patagonia: a new phylogenetic hypothesis for the Interatheriidae, Zoological Journal of the Linnean Society 199 (2), pp. 417-444 : 428

Protypotherium antiquum Ameghino, 1885

( Fig. 4A–B ; Supporting Information, Table S2)

1885 Protypotherium antiquum Ameghino , p. 81–83 (original description).

Lectotype: ZMK 21 /1877 ( Fig. 4A ), right mandibular fragment with p4–m3 (see Fernández et al. 2018), from Late Miocene, Ituzaingó Fm., Entre Ríos Province ( Argentina).

Referred material: IBIGEO-P39 ( Fig. 4B ), less mandibular fragment with p4–m3 ; MCH-P 257, right mandibular fragment with p3–m1 ( Armella and Bonini 2020) .

Extended diagnosis: Protypotherium antiquum differs from Pr. australe , Pr. praerutilum , Pr. columnifer , Pr. compressidens , Pr. minutum , Pr. claudum , and Pr. colloncurensis by having the talonid of m3 with a very deep longitudinal and transverse labial sulcus and a mesio-labial lobe distally straight; from Pr. compressidens by having relatively wider lower cheek teeth; from Pr. claudum by exhibiting a p4 with a transversely deeper, narrower, and more distally placed ectoflexid, and m1–3 with deeper entoflexid; from Pr. colloncurensis and Pr. columnifer by the sub-triangular talonid of p4; from Pr. praerutilum by having a slightly larger size; and from Pr. columnifer by the talonid of p4 narrower than the trigonid.

Geographic and temporal provenance: Entre Ríos Province ( Argentina), Ituzaingó Fm.; Salta Province, Palo Pintado Fm. ( Zimicz et al. 2018); and Catamarca Province, Chiquimil Fm. ( Armella and Bonini 2020); Late Miocene, Huayquerian SALMA.

Measurements: Supporting Information, Table S2.

Remarks: Zimicz et al. (2018) identified IBIGEO-P39 ( Fig. 4B ) as Pr.minutum mainly due to size and a trilobed m3. Nevertheless, these authors mentioned that it resembled the remaining species of the genus. Concerning these features, the presence of a trilobed m3 is common in Protypotherium and it is not exclusive of Pr. minutum (holotype MLP 12-2176) (see above). When comparing the m3 of MLP 12-2176 and IBIGEO-P39, the labial groove of the former is transversally shallow, but persistent, and in both the distal face of the mesio-labial lobe and the disto-labial lobe of the talonid are rounded. Instead, this groove is transversally deeper and persistent in IBIGEO-P39 ( Fig. 4B ) and the distal face of the mesio-labial lobe is straight, which is coincident with the diagnostic features of Pr. antiquum . In addition, IBIGEO-P39 (e.g. Lm1 = 6.26 mm; Wm1 ≈ 3.2 mm) is intermediate in size between Pr. minutum (e.g. Lm1 ≈ 4.6 mm; Wm1 ≈ 2.60 mm) and Pr. antiquum (e.g. Lm1 = 7.4 mm; Wm1 ≈ 4.1 mm (see Supporting Information, Table S2), being even closer to the laưer. Therefore, mainly based on the morphological features, we re-identify IBIGEO-P39 as Pr. antiquum .

On the other hand, we state that MCH-P 257, mentioned as Protypotherium cf. Pr. antiquum by Armella and Bonini (2020), also corresponds to Pr. antiquum , sharing the same mentioned features with IBIGEO-P39.

Figures

Figure 4. Protypotherium antiquum, in occlusal view: (A) ZMK 21/1877, right mandibular fragment with p4–m3; (B) IBIGEO-P 39, less mandibular fragment with p4–m3. Protypotherium australe, in occlusal view: (C) MACN-A 1338 (cast), less maxillary fragment with P3 (broken)–M3. Protypotherium praerutilum, in occlusal view:(D) MACN-A 1081, incomplete skull; (E) MACN-A 3920, complete skull; (F) AMNH 9565, incomplete skull.Protypotherium australe, in occlusal view: (G) MACN-A 9644, incomplete skull. ’ indicates broken tooth. Scale bar = 10 mm.