Prostegotherium sp.

Ciancio, Martín R., Herrera, Claudia, Aramayo, Alejandro, Payrola, Patricio & Babot, Judith, 2016, Diversity of cingulate xenarthrans in the middle-late Eocene of Northwestern Argentina, Acta Palaeontologica Polonica 61 (3), pp. 575-590 : 579-580

? Prostegotherium sp.

Fig. 4B, C .

Material.—MHAS 024 and PVL 6567, two movable osteoderms from Antofagasta de la Sierra, Catamarca Province,

Argentina; middle member of the Geste Formation (sensu Alonso 1992); middle–late Eocene.

Description.—Medium size osteoderms, probably intermediate to the extant species Dasypus hybrids and Dasypus novemcinctus . The exposed surface is smooth, with numerous small pits. The lateral surface is straight and slightly smooth. The principal figure is lageniform with a wide neck and a conspicuous longitudinal keel occupying the entire central region of the osteoderm. At least five to seven foramina occur at the sulcus that encircles the neck of the lageniform main figure. The presence of a row of foramina in the external surface of the osteoderms forming a semicircle is characteristic of Prostegotherium and Riostegotherium ( Astegotheriini ), but Riostegotherium lacks figures and has more foramina. Peripheral figures are defined by a shallow sulcus. The lateral figures are markedly smaller than the anterior ones. The piliferous system is represented by two to five small foramina on the posterior margin.

Measurements.— 10.6–11.3 mm long, 5.2–6.7 mm wide, and 1.9–2.4 mm thick.

Remarks.—The characteristics of the osteoderms are a combination of those of the known species of Prostegotherium (see Vizcaíno 1994) and probably they would represent a new species of this genus. The presence of a sharp medial keel, rugose surface and five small piliferous pits are characteristic of P. astrifer ; but the size and the presence of 4–5 foramina in the external surface of the osteoderm forming an inverted U (not with triangular shape, as P. astrifer ), resembles P. notostylopianum . More and better preserved remains could help a more accurate assignment. Prostegotherium is well represented in early–middle Eocene localities of Patagonia, Argentina (Carlini et al. 2002, 2010; Tejedor et al. 2009; Gelfo et al. 2010; Ciancio et al. 2013a; SOM: Supplementary Online Material available at http://app.pan. pl/SOM/app61-Ciancio_etal_SOM.pdf). In Northwestern Argentina, this genus was recovered at Casa Grande and Quebrada de los Colorados formations ( Herrera and Powell 2009; Herrera et al. 2012; Herrera 2013; see Table 1). The temporal distribution of Prostegotherium provides further evidence to reinforce the interpretation of an Eocene age for Geste Formation ( Powell et al. 2011; Herrera 2013).

Figures

Fig. 4. Dasypodines from the middle member of the Geste Formation, middle–late Eocene, Northwestern Argentina.A. cf. Astegotherium sp., fixed osteoderm, MHAS 067; Quebrada El Paso, near the Pozuelos salt flat, Los Andes Department, Salta Province. B, C.?Prostegotherium sp., movable osteoderms, MHAS 024 (B) and PVL 6567 (C); Antofagasta de la Sierra, Catamarca Province. D−F. Parastegosimpsonia cf. P. peruana, fixed osteoderms, PVL 6569 (D) and MLP 88-V-10-19A (E, broken); movable osteoderm, PVL 6409 (F); Antofagasta de la Sierra, Catamarca Province. G. Dasypodinae indet., movable osteoderm, MLP 88-V-10-19; Antofagasta de la Sierra, Catamarca Province. H−J. Movable osteoderms of Stegosimpsonia (H), Dasypodinae indet. (I) and Anadasypus (J). Photographs (A1−G1), line drawings (A2−G2, H−J). H–J, not to scale.