Pampahippus secundus Deraco and García-López, 2016

Fernández, Mercedes, Zimicz, Ana N., Bond, Mariano, Chornogubsky, Laura, Arnal, Michelle, Cárdenas, Magalí & Fernicola, Juan C., 2021, New Eocene South American native ungulates from the Quebrada de los Colorados Formation at Los Cardones National Park, Argentina, Acta Palaeontologica Polonica 66 (1), pp. 85-97 : 92-94

Pampahippus secundus Deraco and García-López, 2016

Fig. 3C–E .

Holotype: PVL 6426 , right maxillary fragment with P2–M3.

Type locality: El Simbolar, Guachipas Department, Salta Province, Argentina.

Type horizon: Upper section of the Lumbrera Formation, middle Eocene.

Material.—IBIGEO-P 62, right trigonid and incomplete talonid of a lower molar ( Fig. 3C ), and an upper fragmented cheek tooth; IBIGEO-P 63 ( Fig. 3D ), fragmented left p3 or p4; IBIGEO-P 64 ( Fig. 3E ), left m1?. Quebrada Grande, Los Cardones National Park, Casamayoran SALMA.

Description.—IBIGEO-P 62–64 are brachydont cheek teeth, subrectangular in outline. Although IBIGEO-P 63 is broken, it is probable that this cheek tooth is a p3 or p4 due to the following characteristics; the trigonid and talonid are separated by a deep labial sulcus; the cristid obliqua is connected to the distal wall of the metalophid; the metalophid is straight and disto-lingually directed; the talonid is short and shows a conspicuous bunoid and isolated entoconid; the hypoconulid is located distal to the distal wall of the entoconid. IBIGEO-P 62 is a molariform cheek tooth; due to its breakage it is not possible to determine which tooth it is, but some recognizable features and the absence of others allow us to infer that it could be a lower molar; the trigonid is subrectangular in outline, being wider than long; the protolophid is almost straight; the paralophid is short, narrow, and lingually directed; the mesio-lingual cingulid is reduced and separated from the lingual region of the paralophid, but, based on the height of the cingulid on the crown, its location on the trigonid, and its proximity to the paralophid, with wear, the mesio-lingual cingulid fuses to the paralophid; a small cusp is identified between these structures; the trigonid presents a conspicuous paraconid mesial to the mesio-labial wall of the metalophid; the metalophid is straight, conspicuous, and disto-lingually directed; the cristid obliqua is united to the labial portion of the metalophid; the labial sulcus is transversally and longitudinally deep; the talonid is larger and lower than the trigonid, and subquadrangular in outline; there are no traces of labial and lingual cingulids. In IBIGEO-P 64, the protolophid is almost straight and mesio-labially directed; despite the breakage of the paralophid, it seems to be disto-lingually directed; the metalophid is straight and disto-lingually directed; the paraconid is conspicuous and connected to the mesio-labial face of the metalophid; the cristid obliqua is connected to the labial portion of the metalophid; the labial sulcus is transversally and longitudinally deep; the talonid is labially convex, and larger and slightly lower than the trigonid, but both present almost the same width; the talonid basin is shallow and wide; the lophoid entoconid is well developed and transversally expanded, connected to the hypoconid region, and separated from the hypoconulid by the a small disto-lingual valley, which is limited by a disto-lingual cingulid that connects the hypoconulid and the entoconid; the hypolophid is moderately short and curved as it slightly protrudes from the distal face of the entoconid; there are no traces of labial or lingual cingulids. To sum up, IBIGEO-P 62–64 present a combination of characteristics, including their size, the mesio-distal expansion of lower cheek tooth, the identification of a small paraconid mesial to the metaconid, the presence of a well-developed entoconid being bunoid in premolars and lophoid in molars, and the absence of lingual and labial cingulids on molars, all of which allowing their identification as Pampahippus secundus .

Stratigraphic and geographic range.— Lower and upper sections of the Lumbrera and Quebrada de Los Colorados Formations, middle Eocene; Salta Province, Argentina.

Remarks.— Pampahippus secundus has been identified in the lower ( Deraco and García-López 2016) and upper levels ( García-López et al. 2019) of the Lumbrera Fm., at El Simbolar (Salta). In addition, Pampahippus has also been recognized in the lower section of the Lumbrera Fm. at Pampa Grande, Salta (Bond and López 1993), Quebrada de Los Colorados Fm. at La Poma, Salta ( García-López et al. 2018), and Geste Fm. at Antofagasta de la Sierra, Catamarca López 1997).

Figures

Fig. 3. New fossil specimens of Typotheria and Toxodontia from the Quebrada de Los Colorados Formation exposed at Quebrada Grande locality, Los Cardones National Park (Salta Province), Casamayoran SALMA. A, B. Colbertiasp. A. IBIGEO-P 58a, left maxillary fragment with M2–M3 in occlusal view.B. IBIGEO-P 58b, left maxillary fragment with P4–M3 in occlusal view.C–E. Pampahippus secundus Deraco and García-López, 2016. C. IBIGEO-P 62, right trigonid and incomplete talonid of a lower right molar in occlusal view. D. IBIGEO-P 63, fragmented left p3 or p4 in occlusal view. E. IBIGEO-P 64, left m1? in occlusal (E1), labial (E2), and lingual (E3) views. Photographs (A1–E1, E3, E4), explanatory drawings (A2–E2). Dashed area indicates broken or missing dental areas.