Histology of Extra-Carapacial Osteoderms of Glyptodon reticulatus Owen, 1845 (Mammalia, Xenarthra) from the Late Pleistocene of Argentina

HARO JOSÉ AUGUSTO ; BRAMBILLA LUCIANO; BRUN, LUCAS R; IBARRA DAMIÁN ; ZUCCARI IGNACIO ; MARCHETTO JOSÉ

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2020 vol. 101 p. 1 - 8

0895-9811

The osteoderms of Glyptodonreticulatus not belonging to the dorsal cuirass are very variable both morphologically, with scalloped, globular, and flattened varieties, and histologically. The flattened and scalloped ones lack a cancellous bone core, unlike those from the dorsal cuirass. The scalloped variety present a few large cavities. The globular one is, on the other hand, finely cancellous. Their structure is characterized by extensive remodelling and the presence of thick fiber bundles. The latter are more abundant in the scalloped variety. The amount of remodelling and the fiber bundles perpendicular to the inner surface more closely resembles many dorsal cuirass osteoderms of Glyptodon than those previously described for Glyptotherium, but assessment of the taxonomic value of the former trait requires determination of similarity in age or size at death. On the other hand, these characters do not allow distinction from Panochthus and Doedicurus. Histological distinction from sloth osteoderms was not possible because of the variability in the latter in remodelling, presence of resorption spaces, and of an external fundamental system with fine fiber bundles perpendicular to the bone surface. The lack of evidence of woven bone and of centripetal, non-osteonal lamellar or parallel-fibered bone in the scalloped variety suggests ossification was mostly metaplastic. The flattened osteoderm, on the other hand, presents evidence of woven bone. This suggests variation may have existed in the mineralization process of different kinds of osteoderms.