Pachyarmatherium sp.

† Pachyarmatherium sp.

( Fig. 2B 1–D 2)

Referred specimens. Three isolated fixed osteoderms from the part of the carapace not corresponding to a movable band. (MTT-V-212, -358, -479).

Locality. Cucuruchú (Las Dunas) site ( Fig. 1).

Description. Osteoderms are hexagonal to heptagonal (e.g., MTT-V-212), very thick in the anterior portion and reducing its thickness to the distal portion, but thicker than the described osteoderms in P. leiseyi , P. tenebris and P. brasiliense in the later part (Downing & White 1995, Rincón & White 2007; Porpino et al. 2009); slightly longer than wide, including a rough and convex external surface with the central figure forming the highest relief as in P. tenebris (Rincón & White 2007, figs. 2–3) and less pronounced than in P. leiseyi (Downing & White 1995, figs. 1–2). There are four to six peripheral figures, which are larger on the anterior margin, reducing significantly in size distally; the central figure is rounded or polygonal as in P. leiseyi and P. tenebris (Downing & White 1995, figs. 1–2; Rincón & White 2007, figs. 2–3), defined by a deep and well-marked main sulcus. The central figure is large, encompassing most of the external surface of the osteoderm and posteriorly displaced. The radial sulci are deep, short and well-defined (except in MTT-V-212). The piliferous foramina are at the intersection between the main/central sulcus and the peripheral sulci ( Fig. 2B 1, C1, D1), being large and well-marked. Specimen MTT- V-358 has a large foramen on the central figure and a series of medium to small-sized foramina scattered throughout this area, giving it a rough and stippled appearance. The internal surface is flat and somewhat concave, as in P. leiseyi (Downing & White 1995, fig. 1), and exhibits three to five vascular foramina.