Megalonychidae

Megalonychidae is a family of sloths within the order Pilosa. Traditionally it included the living two-toed sloths of the genus Choloepus and several extinct ground-sloth lineages, notably Megalonyx; in some modern classifications the living two-toed sloths are placed in a separate family or subfamily, and the exact composition of Megalonychidae has varied among systems.

Extant members, the two-toed sloths (Choloepus), inhabit tropical forests of Central and South America and lead mainly arboreal, folivorous lives. They are characterized by two large claws on each forelimb and three on each hind limb, a relatively slow metabolism, and a highly energy-efficient, low‑activity lifestyle that allows them to survive on leafy diets. Two-toed sloths are typically solitary and have long grooming and resting periods, which contribute to their slow pace of life.

The fossil record for Megalonychidae extends back to the Miocene, with several extinct genera such as Megalonyx appearing in North and Central America during the Pliocene and Pleistocene. This contrasts with the modern two-toed sloths, which are limited to the Americas south of the United States today. Differences in dentition, skull morphology, and limb structure distinguish megalochyid sloths from related families such as Bradypodidae, the three-toed sloths.

Conservation concerns for Megalonychidae arise primarily from habitat loss and fragmentation in tropical forests. While many living two-toed sloths are not classified as endangered, regional populations can be threatened by deforestation and human activity. The name Megalonychidae is derived from Megalonyx, meaning “great claw.”