Panochthus jaguaribensis Moreira, 1965

Pereira, Paulo Victor Luiz Gomes Da Costa, Victer, Gustavo Duarte, Porpino, Kleberson De Oliveira & Bergqvist, Lílian Paglarelli, 2014, Osteoderm histology of Late Pleistocene cingulates from the intertropical region of Brazil, Acta Palaeontologica Polonica 59 (3), pp. 543-552 : 547-549

Panochthus jaguaribensis Moreira, 1965

Fig. 5 .

Material.—Carapace fragment (MCC 1089V, section UFRJ-DG 494-M) from Lagoa do Santo, Currais Novos municipality, Rio Grande do Norte, Late Pleistocene.

Description.—MCC 1089V represents a small fragment of the carapace of Panochthus jaguaribensis . In external view, the fragment is covered by several tiny, quadrangular to hexagonal figures, as well as some large, flat, subcircular main figures delimited by thin sulci with several small pits ( Fig. 5A 1 ). The internal surface is concave and perforated by large neurovascular foramina ( Fig. 5A 3 ).

In cross section, there are two weakly developed layers of compact bone adjacent to the external and internal surfaces Fig. 5B 1 , B 2 ). The superficial layer of compact bone is highly vascularized and contains some randomly distributed primary and secondary osteons. Near the surface, there are narrow collagen fibers with no preferential orientation ( Fig. 5B 1 ). The central region of the osteoderm is composed of thin trabeculae with both primary and secondary osteons, outlining large and rounded resorption areas. Toward the center of the osteoderm, the resorption areas become smaller and more elongated. At its greatest extent, the deep layer of compact bone is thicker than the superficial one, but becomes thinner toward the periphery and has fewer osteons than the latter. Collagen fibers run obliquely or perpendicularly to the internal surface ( Fig. B 3 ). They seem to originate from outside the osteoderm, and therefore probably represent Sharpey fibers.

Stratigraphic and geographic range.—Late Pleistocene of northeastern Brazil.

Family Glaptodontidae Gray, 1869

Genus Glyptotherium Osborn, 1903

Type species: Glyptotherium texanum Osborn, 1903 ; Late Pliocene– Early Pleistocene , Texas, United States .

Glyptotherium sp.

Fig. 6 .

Material.—Uncatalogued isolated osteoderm (section UFRJ-DG 493-M) forming part of the carapace (MCC collection) from Lajedo da Escada, Baraúna municipality, Rio Grande do Norte, Late Pleistocene.

Description.—In external view, the osteoderm is hexagonal, bearing a roughly textured surface with hundreds of small, shallow, subcircular or irregularly-shaped pits. In the center of the external surface, the main figure is surrounded by seven slightly smaller peripheral figures, separated by well-defined sulci ( Fig. 6A 1 ). Four large, deep perforations, probably piliferous foramina or glandular pits, occur at the intersection of the radial sulci with the main sulcus. The surface of the peripheral and the main figures are flat. The internal surface is gently concave and perforated by several small foramina ( Fig. 6A 3 ).

In cross section, the microstructure of the osteoderm is porous and highly vascularized. The superficial and deep layers of compact bone are darker than other areas of the osteoderm and poorly developed ( Fig. 6B ). The superficial layer 1

of compact bone contains numerous primary osteons and is characterized by a mosaic-like structure ( Fig. 6B 2 ). Near the external surface, mainly on the left side, narrow collagen fibers occur and are predominantly oriented parallel to the surface, although some are slightly oblique. Pits which likely housed hair follicles appear as deep excavations ( Fig. 6B 1 ).

The central region of the osteoderm is composed of trabecular bone with small to medium-sized resorption areas and some secondary osteons. One section in particular stands out for being composed of a vertical sequence of transversely elongated, parallel resorption areas ( Fig. 6B 1 ). The deep layer of compact bone is thinner than the superficial one, especially on the sides ( Fig. 6B 3 ), and contains some primary and secondary osteons.

Figures

Fig. 5. Carapace fragment of Panochthus jaguaribensis Moreira, 1965 from the Late Pleistocene of Lagoa do Santo site, Currais Novos municipality, Rio Grande do Norte State, Brazil. A. MCC 1089V, carapace fragment in external view showing the superficial ornamentation (A 1), lateral (A 2) and deep (A 3) views. B. UFRJ-DG 494-M; internal structure of the osteoderm (B 1). Paleohistological sections viewed under a petrographic microscope, superficial compact bone with primary osteons, secondary osteons and mineralized fiber bundles (B 2); deep layer of compact bone and trabecular bone with some resorption areas (B 3). Some possible mineralized fiber bundles also occur.Scale bars:A, 30 mm; B 1, 5 mm; B 2, B 3, 1 mm.Abbreviations:mfb, mineralized fiber bundles; po, primary osteon; ra, resorption area; so, secondary osteon.

Fig. 1. Simplified cladogram showing the phylogenetic relationships of cingulates, modified from Gaudin and Wible (2006) and Porpino et al. 2009). Note that dasypodids, a group traditionally recognized in the systematics of the xenarthrans, actually represent a paraphyletic assemblage.

Fig.3. Uncatalogued isolated osteoderm of the carapace of Pachyarmatherium brasiliense Porpino, Fernicola, and Bergqvist, 2009 from the Late Pleistocene of Lajedo da Escada site, Baraúna municipality, Rio Grande do Norte State, Brazil. A. Osteoderm in external view showing the superficial ornamentation (A 1),lateral (A 2)and internal (A 3)views.B. UFRJ-DG 492-M, internal structure ofthe osteoderm (B 1). Paleohistologicalsections viewed under a petrographic microscope, superficial layer of osteoderm (B 2), note the darker region near the top of the section and the uniform distribution of primary osteons marked by pointers; deep layer of compact bone with dark areas (B 3). Scale bars:A, 10 mm; B 1, 3 mm; B 2, B 3, 1 mm.Abbreviations:da, dark areas (see text for details); po, primary osteon; ra, resorption area; so, secondary osteon.

Fig. 2. Distribution of the studied species within Brazil. Based on Porpino 2009), Porpino and Bergqvist (2002), and Oliveira et al. (2010).

Fig. 6. Uncatalogued isolated osteoderm of the carapace of Glyptotherium sp. from Late Pleistocene of Lajedo da escada site, Baraúnas municipality, Rio Grande do Norte State, Brazil. A. Osteoderm in external (A), lateral (A), and deep (A) views. B. UFRJ-DG 493-M; internal structure of the 1 2 3 osteoderm (B 1), note the shelf-like structure (ellipse). Paleohistological sections viewed under a petrographic microscope; superficial (B 2) and deep B 3) layers. Scale bars:A, 10 mm; B 1, 5 mm; B 2, B 3, 1 mm. Abbreviations: ms, mosaic-like region; mfb, mineralized fiber bundles; ra, resorption area; so, secondary osteon.