Parutaetus punaensis, Ciancio & Herrera & Aramayo & Payrola & Babot, 2016

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 : 581-583

Parutaetus punaensis sp. nov.

Fig. 5 .

Etymology: In reference to the Puna, the South American ecoregion where the type locality is located.

Holotype: MLP 83 -XI-3-2 ( Fig. 5A ), two fixed osteoderms, one movable osteoderm, and several fragments. All these pieces are associated and included in the same lot.

Type locality: Quebrada El Paso, near Pozuelos salt flat, Los Andes Department, Salta Province, Argentina.

Type horizon: Middle member of the Geste Formation (sensu Alonso 1992); middle–late Eocene.

Material.—MHAS 017–020, 029, PVL 6416, 6575, 6403, 6413–6415, 6407, 6417, 6568, MLP 86-V-6-24, 86-V-6-25, 93-IV-1-17, 93-IV-1-18, fixed and movable osteoderms of the dorsal shield. All specimens from Antofagasta de la Sierra,

Catamarca Province, Argentina; middle section of the Geste Formation (sensu Alonso 1992); middle–late Eocene.

Diagnosis.—Osteoderms larger than those of other species of the genus, external surface of osteoderms smooth but with numerous small pits. The central figure of the fixed osteoderms is long but does not reach the posterior margin. This figure widens gradually toward the anterior border, differing from other Parutaetus species where the shape changes sharply. The anterior figures are polygonal and well developed as in P. chicoensis and P. chilensis . The anterolateral figures are triangular to subtrapezoidal and smaller than the long posterolateral figures. The anterior portion of the main figure bears two to five well-developed foramina in the intersection of the sulci that delimit the anterior figures from the central one. The piliferous system is restricted to the posterior margin and is poorly developed; it consists of two to five small, well-separated foramina; this trait differs from P. chilensis that exhibit two foramina. The movable osteoderms bear two longitudinal grooves dividing the surface into three low ridges. The central one, the principal figure, is wider anteriorly and thins gradually toward the posterior border. The lateral figures are divided by two shallow transverse sulci in the anterior half of the osteoderm, resulting in two anterolateral figures that are substantially shorter than the posterolateral ones. This pattern differs from P. chilensis which bears only one division and hence only one anterolateral figure, and from P. chicoensis , wherein the transverse sulci are absent. There are two piliferous foramina in each posterior corner.

Measurements.—MLP 83-XI-3-2, holotype, fixed osteoderms: 12.5 mm length, 6.4–7 mm width, and 3.3 mm thick; movable osteoderms: 21.6 mm length, 8 mm width, and 3 mm thick. Measurements of fixed osteoderms (referred material): 9–12 mm long, 5.5–9 mm wide, and 3–4.5 mm thick.

Description.—Small size, similar to extant Chaetophractus villosus . The osteoderms are smooth, with the contact areas between adjacent osteoderms smooth, concave in section, and with scattered small denticular projections. The fixed osteoderms range from pentagonal at the medial region, to rectangular or cuadrangular towards the lateral portion of the carapace. The figures are convex and well defined by narrow furrows. The main figure is wide at the anterior third and narrower backwards; it extends close to but does not contact the posterior margin. This figure is surrounded by a pair of anterior polygonal figures, two triangular to trapezoidal anterolateral, and two posterolateral ones. The anterolateral figures form a complex rhomboidal figure with those of the adjacent osteoderms. This condition is interpreted as an area covered by a single horny scale, feature present in some basal fossil Dasypodidae .Despite this general description, we identify two different morphotypes of fixed osteoderms, based in the variation of the osteoderm morphology observed in some primitive euphractins, such as Utaetus buccatus , Parutaetus chilensis , Amblytatus , Isutaetus (see Ciancio and Carlini 2008; Carlini et al. 2009, 2010). One group, probably from the lateral zones of the pelvic buckler ( Fig. 5A–I ), are rectangular (those defined in the diagnosis); and the other, interpreted as part of the central region of the pelvic buckler, includes pentagonal and almost as long as wide osteoderms. The second group of osteoderms ( Fig. 5L–Q ) is defined characteristics by the development of a semicircular sulcus (instead of singular foramina) in the anterior portion of the main figure. It is common to find this structure in some osteoderms of the central medial zone of the pelvic buckler of euphractins, generally associated to hypertrophied glands. Besides, the main figure is shortened and incorporates the posterolateral figures, acquiring a bell-shaped, and the anterolateral figures are triangular in shape (with the base directed laterally) and generally reach the posterior border. There are small accessory peripheral figures that do not contact with the principal ones in the anterior border of some osteoderms. The triangular lateral figures form a complex rhomboidal figure with that of the adjacent osteoderm. This condition is interpreted as an area covered by a single horny scale, and this characteristic occurs in some basal Dasypodidae .

The movable osteoderms ( Fig. 5J, K ) have a well-defined overlapping portion. In the external surface of the main portion of the osteoderm, there are two longitudinal furrows that define three elongated figures, one central and two laterals. Lateral figures are divided by two transverse furrows on the anterior third, which define two anterolateral figures and a longer posterior one. There are two pairs of foramina on the surface, at the intersection of the furrows that limit the figures. The piliferous system is poorly developed, with two foramina on the posterior corner of the osteoderm.

Remarks.—In previous works, some of the isolated osteoderms described here were identified as Utaetus (PVL 6403), a genus restricted to the Barrancan Subage (Casamayoran SALMA) of Patagonia, Prostegotherium notostylopianum (PVL 6407), Prostegotherium (MLP 86-V-6-24, 86-V-6-25, PVL 6413-6420), and Astegotherium (PVL 6412) ( Powell et al. 2011; López 1997).

This is the first record of Parutaetus in Northwestern Argentina. This genus is known in post Casamayoran–pre Deseadan faunas (middle–late Eocene to early Oligocene) from Patagonia ( Ciancio and Carlini 2008; Carlini et al. 2010) and Central Chile (Tinguiririca; Carlini et al. 2009).

Stratigraphic and geographic range.— Quebrada El Paso, near Pozuelos salt flat, Los Andes Department, Salta Province and Antofagasta de la Sierra, Catamarca Province, Argentina; middle section of the Geste Formation (sensu Alonso 1992); middle–late Eocene .

Figures

Fig. 5. Osteoderms of euphractin Parutaetus punaensis sp. nov. from the middle member of the Geste Formation, middle–late Eocene, Northwestern Argentina. A. Holotype, MLP 83-XI-3-2; Quebrada El Paso, near the Pozuelos salt flat, Los Andes Department, Salta Province. B–E. Fixed osteoderms from Antofagasta de la Sierra, Catamarca Province; morphotype assigned to the lateral zones of the pelvic buckler, MLP 93-VI-1-17 (B, D), MLP 86-V-6- 25 (C, E, F–I), and movable osteoderms, MLP 86-V-10-19 (J), MLP 93-VI-1-18 (K). L–Q. Fixed osteoderms from Antofagasta de la Sierra, Catamarca Province; morphotype assigned to the medial zone of the pelvic buckler, MLP 88-V-10-18 (L), MLP 86-V-6-24 (M–P), MLP 86-V-6-25 (Q). Photographs A, B1−Q1), line drawings (B2−Q2).