Neck osteoarthritis in Eremotherium laurillardi (Lund, 1842; Mammalia, Xenarthra) from the Late Pleistocene of Brazil

• Osteoarthritis is diagnosed for a Late Pleistocene ground sloth of Brazil.
• The disease was located in an unexpected joint (atlanto-axial) of the skeleton.
• Aging may be the cause of the osteoarthritis.
• Osteoarthritis is located in a bone unrelated to weight support.

Paleopathological analyses of Brazilian Quaternary mammals remain scarce. However, this type of study can shed light on several paleoecological issues in vertebrate paleobiology and taphonomy. Here, we describe and diagnose a pathology on an axis of a ground sloth Eremotherium laurillardi (Lund, 1842) from Pernambuco State, Brazil. Through the identification of osteophytes, we define an osteoarthritic lesion in the atlantoaxial joint (C1–C2), which is unrelated to body weight support. Thus, this paper reports a peculiar allocation of osteoarthritis in a mammalian skeleton. We did not attribute such alteration to calcium pyrophosphate deposition disease (CPPD) because the bone elevation occurs only on the borders of the lateral articular facets of the axis, and not on the joint surface. This analysis shows that osteoarthritis can also occur in regions of vertebral column that are not weight-bearing, which is one of the main predisposing factors for this disease.