The oldest record of bone diseases in Xenarthra (Mammalia)

Abstract

Paleopathological studies are a useful tool for paleobiological and paleoecological interpretations in different extinct vertebrate clades. The Xenarthra are one of the groups of fossil mammals that has received the most attention regarding these type of analyzes in the last years. However, all pathological records are restricted to the Quaternary sloths and glyptodonts of South America. In this contribution we present different articular and vertebral lesions in three specimens of Simomylodon Saint-André et al., 2010 (Mylodontidae) from the Late Miocene-Pliocene of Jujuy province (northwestern Argentina). Although each individual show lesions in different degree, they present the same types of bones changes. The non-marginal syndesmophyte on the axis/third cervical vertebrae (JUY-P-084) and on sacral vertebrae (JUY-P-185), marginal bone overgrowth and peripheral joint erosion on the lateral and medial condyle in the femur (JUY-P-185) and articulate surface for tibia of the astragalus (JUY-P-089) are diagnostic of spondyloarthropathy (SpA). The presence of calcified plate-like on the joint surfaces of the vertebrae of all individuals indicates the secondary development of Calcium Pyrophosphate Deposition Disease (CPPD), a type of inflammatory, mechanical and crystalline arthritis, probably as a complication of SpA. On the other hand, osteophytes on the edges of vertebral endplates are indicative of spondylosis deformans, an aging condition. These lesions correspond to the oldest record of pathologies in sloths, and in xenarthrans in general. Finally, it is noteworthy that all specimens are adults having different body sizes, indicating that the development of these diseases seems to be unrelated to the weight of these mammals. *Financiamietno: PICT 0765, PI Q002.