Homalostylops sp.

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 : 89

? Homalostylops sp.

Fig. 1D .

Material.—IBIGEO-P 57a, left m1?, Quebrada Grande, Los Cardones National Park, Casamayoran SALMA, Eocene.

Description.—IBIGEO-P 57a is a worn cheek tooth, probably the m1. It is a low-crowned tooth, subrectangular in outline; the trigonid is simple and presents a subrectangular contour, being wider than long; the protolophid is short and mesio-lingually directed; the paralophid is more developed than the protolophid, and has already been fused to the mesial cingulid, deriving in an slightly disto-lingually directed lophid; the metalophid is almost transversal and well developed, protruding more lingually than the paralophid, and there is no trace of a paraconid or any accessory cuspid. The talonid is well developed and subquadrangular in outline, it is much longer than the trigonid, but both present a similar width; the cristid obliqua is conspicuous, and it is connected to the labial portion of the metalophid; the labial sulcus is transversally deep; there are traces of the disto-lingual sulcus that separates the hypoconulid from the distal face of the entoconid.

Remarks.—As mentioned above, the specimen IBIGEO-P 57a is very worn cheek tooth, but its morphology and size (see Table 1 ) fit well within the general characteristics and size recorded for the m1 in other species of Homalostylops (see Simpson 1948 for comparative measurements). Nevertheless, and mainly due to the heavy state of wear, we refer this specimen with doubts to the genus Homalostylops .

Figures

Fig. 1. New fossil materials of Litopterna,Astrapotheria, and Notostylopidae from the Quebrada de Los Colorados Formation exposed at Quebrada Grande locality, Los Cardones National Park (Salta Province), Casamayoran SALMA, Eocene. A. cf. Ernestokokenia sp. (IBIGEO-P 65), fragmented left upper cheek tooth in occlusal view.B.Astrapotheria indet.(IBIGEO-P 66), left maxillary fragment with three broken molariforms in lingual (B1) and occlusal (B3) views, and detail showing Hunter-Schreger bands (B4); dashed area in B2 indicates broken or missing dental areas. C. Homalostylops sp. (IBIGEO-P 57b), right m2? in occlusal (C1), lingual (C3), and labial (C4) views. D.?Homalostylops sp. (IBIGEO-P 57a), left m1? in occlusal view. Photographs (A1, B1, B3, B4, C1, C3, C4, D1), explanatory drawings (A2, B2, C2, D2).