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Xenarthra (cohort Unguiculata, order Edentata) A suborder that comprises the infra-orders Cingulata and Pilosa, the S. American edentates known since the Eocene and characterized by additional articulations in the lumbar vertebrae (the name of the suborder means ‘extra-jointed’), the union of the ischium and the caudal vertebrae, and a distinctive skull structure. The claws are well developed: in the arboreal sloths they are used for hanging below the branches of trees, in other families they are used for digging and oblige the animals to walk on the sides of their feet. The infra-orders distinguish between the forms with hair (the ant-eaters and sloths) and those with ‘shells’ (the armadillos).