Protypotherium australe ( Ameghino, 1887a )

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 : 428-429

Protypotherium australe ( Ameghino, 1887a)

( Figs 2D–E, G, I–J, L , 3B, F–M , 4C, F , 5–7 ; Supporting Information, Table S2)

1882 Toxodontophanus australis Moreno , p. 23 (nomen nudum).

1887a Toxodontophanus australis Ameghino , p. 64 (original description).

1887b Protypotherium australe ( Ameghino, 1887a) ; Ameghino, p. 63.

1909 Patriarchus furculosus Ameghino, 1891b ; Sinclair, p. 33.

1909 Patriarchus distortus Ameghino, 1891b ; Sinclair, p. 33.

1909 Patriarchus altus Ameghino, 1891b ; Sinclair, p. 34.

Epipatriarchus bifidens Ameghino, 1904 ; regarded as synonym herein.

Protypotherium martini Lane, 1927 ; regarded as synonym herein.

Holotype: MACN-A 1338 and MACN-A 1345–1346 ( Fig. 4C ), casts of the missing holotype with less maxillary fragment with P3–M3 (see Fernández et al. 2018), Early–Middle Miocene , SCF, Santa Cruz Province ( Argentina).

Referred materials: Supporting Information, Table S1 .

Extended diagnosis: Protypotherium australe differs from Pr. praerutilum by being larger (~20%) and I1 longer than I2–3; from Pr. antiquum by the talonid of m3 with a shallower (and even absent) labial groove, and its mesial lobe with its distal region concave; from Pr. colloncurensis and Pr. columnifer by the talonid of p2–4 sub-triangular in outline; from Pr. compressidens by exhibiting wider cheek teeth, in particular P2–M3; from Pr. colloncurensis by a descending process of the maxilla with a moderate development; from Pr. claudum by having p2–3 with a distinctive entoflexid, p4 with a transversely deeper, narrower and more distally-placed ectoflexid, and m1–3 with deeper entoflexids; from Pr. minutum and Pr. distinctum by having less cement covering the cheek teeth, the P2–4 with an entoflexus located in a more distal position and slightly less expanded, and M1–3 with straighter ectolophs; and from Pr. columnifer by the talonid of p4 narrower than the trigonid.

Geographic and stratigraphic provenance: Santa Cruz Province ( Argentina), SCF, Early – Middle Miocene, Santacrucian SALMA; Río Negro , Chubut, and Neuquén Provinces ( Argentina), Collón Curá Fm., Middle Miocene, Colloncuran SALMA; south-western Chubut and north-western Santa Cruz provinces, Late Middle Miocene, ‘ Mayoan’ SALMA.

Measurements: Supporting Information, Table S2.

Remarks: Lane (1927) differentiated Pr. martini from the other species of Protypotherium by the apparent narrowness of M1 ( R W/L = 0.56), the width of P2–4 ( R W/L = 1.00, 1.25, and 1.11, respectively), and the presence of an acute disto-lingual margin. The author highlighted that the remaining dental characteristics, as well as the dental height, coincide with those of Pr. australe . Nevertheless, not only was the sample studied by Lane (1927) very small (four specimens) in comparison to its abundance in the SCF, but also the values provided by the author fall within the range of variation obtained here for Pr. australe (M1, 0.55 ≤ R W/L ≤ 0.8; P2, 0.6 < R W/L ≤ 1.37; P3, 0.72 ≤ R W/L ≤ 1.19; P4, 0.6 < R W/L <1.2). Regarding the acute disto-lingual margin, this is a variable feature not only for Pr. australe , but also for Pr. praerutilum . Therefore, Pr. martini is herein considered junior synonym of Pr. australe .

Vera et al. (2018) reviewed the genus Epipatriarchus and stated that the type materials of the type species, Ep. bifidens (currently missing, but figured by Rovereto 1914: figs 1–2), are assignable to Protypotherium cf. colloncurensis . However, this identification was supported by the geographic and stratigraphic provenance of the type materials of Ep. bifidens and Pr. colloncurensis , assumed to be the same by the authors. The provenance of these specimens is not entirely clear (and much less the stratigraphic provenance) as it happens with most materials housed at the old palaeontological collections, and it should not be used as a criterion for taxonomic identification. The illustrations in Rovereto (1914: figs 1–2) do allow us to agree with the generic assignment proposed by Vera et al. (2018), but the dental morphology, particularly that of the lower teeth, and the dimensions (asser Ameghino 1904), align with those of Pr. australe (see Supporting Information, Table S2). For instance, Ep. bifidens has lower premolars with sub-triangular talonids smaller than trigonids, as in Pr. australe , whereas Pr. colloncurensis has sub-circular talonids much smaller than trigonids. Therefore, Ep. bifidens is considered here as a junior synonym of Pr. australe .

Figures

Figure 2. Protypotherium australe (D–E, G, I–J, L) and Pr. praerutilum (A–C, F, H, K, M), in occlusal view. (A) YPM-VPPU 15386, incomplete skull; (B) less I3 (alveolus)–C–dP1–P2–M3 of MACN-A 4049; (C) less I3–dP1–M3 of MACN-A 4278; (D) right I1 (alveolus)–dP1–P2–M3 of MACN-A 3882; (E) right I1–dP1–P2–M3 of MACN-A 9623–9633; (F) less I1 (alveolus)–dP1–P2–M3 of AMNH 9187; (G) right I1–2 (alveolus)–dP1–P2–M3 of YPM-VPPU 15643; (H) MLP 12-2886, incomplete skull; (I) right I1 (alveolus)–I2–dP1–P2–M3 of MACN-A 37; (J) MACN-A 3911, less maxillary fragment with C–dP1–P2–M3; (K) MACN-A 1778, right maxillary fragment with dP1–P2 (alveoli)– P3–M3; (L) right I1 (alveolus)–dP1–P2–M3 of AMNH 9149; (M) MACN-A 4016, less maxillary fragment with P4–M3.* indicates alveolus. Scale bar = 10 mm.

Figure 3. Protypotherium australe (B, F–M) and Pr. praerutilum (A, C–E), in occlusal view. (A) MACN-A 3952, right mandibular fragment with p3–m3; (B) less dp1–p2–m3 of AMNH 9286; (C) MACN-A 11191a, right mandibular fragment with m1–3; (D) right p2–m3 of MACN-A 9614; (E) right i1–dp1–p2–m3 of MACN-A 1082; (F) less p4–m3 of AMNH 9565; (G) right p2–m3 of AMNH 9149; (H) less i1–dp1– p2–m3 of MPM-PV 3531; (I) MACN-A 532, right mandibular fragment with m2–3; (J) right p2–m3 of MPM-PV 3739; (K) MPM-PV 19612, right mandibular fragment with m2 (broken)–3; (L) MACN-A 3979, less mandibular fragment with p3–m3; (M) MACN-A 3955, less mandibular fragment with p3–m3. * indicates alveolus; ’ indicates broken tooth. Scale bar = 10 mm.

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.

Figure 5. Scaưer diagram of the Santacrucian species of Protypotherium (except for Pr.claudum). A, Length vs.width of M1. B, Length vs. width of m1. Abbreviations: L, length; W, width.

Figure 6. Scaưer diagram of the Santacrucian species of Protypotherium (except for Pr.claudum). A, Length vs. width of M2. B, Length vs. width of m2. Abbreviations: L, length; W, width.

Figure 7. Box-plot showing the length of I1–3 in: (A) Pr.praerutilum; (B) Pr.australe.