xenarthran

Xenarthra is a superorder of placental mammals that comprises the extant armadillos, anteaters, and sloths. The name, meaning “strange joints,” refers to the xenarthrous articulations found in their spine and, in some cases, forelimbs. These joints, along with other skeletal and dental traits, help distinguish xenarthrans from most other mammals.

Within Xenarthra, two major lineages are recognized: Cingulata, the armadillos, and Pilosa, which includes Vermilingua (anteaters) and Folivora (sloths). The group is native to the Americas, with the greatest diversity in South America; today species occur from southern North America to Argentina, occupying forests, grasslands, and deserts.

Evolutionarily, xenarthrans likely diverged from other placentals in the early Cenozoic. Much of their early diversification occurred in South America during its long isolation. Many extinct relatives, such as glyptodonts and pampatheres, belonged to the armadillo lineage, while the sloth and anteater lineages produced numerous fossil forms before and after the Great American Interchange.

Ecology and adaptations vary by group. Armadillos often have a bony armor and are proficient diggers; anteaters specialize in insectivory with elongated snouts and long tongues; sloths are slow-moving, arboreal folivores with long claws and notably low metabolic rates. Teeth are reduced or absent in several species, reflecting dietary specializations.

Conservation concerns affect xenarthrans in many regions, driven by habitat loss, road mortality, and hunting. Several species are threatened, and conservation efforts focus on habitat protection, wildlife corridors, and mitigating human-wildlife conflict.