Nothrotheriidae

Nothrotheriidae is a family of extinct ground sloths that lived from approximately 17.5 mya—10,000 years ago, existing for approximately . Previously placed within the tribe Nothrotheriini or subfamily Nothrotheriinae within Megatheriidae, they are now usually placed in their own family, Nothrotheriidae. Nothrotheriids appeared in the Burdigalian, some 19.8 million years ago, in South America. The group includes the comparatively slightly built Nothrotheriops, which reached a length of about . While nothrotheriids were small compared to some of their megatheriid relatives, their claws provided an effective defense against predators, like those of larger anteaters today.

== Evolution == It has been proposed that the progressive increase in body sizes among nothrotheriids over their evolution is related to their increasingly terrestrial habits and lifestyles. During the Late Miocene and Pliocene, the sloth genus Thalassocnus of the west coast of South America became adapted to a shallow-water marine lifestyle. However, the family placement of Thalassocnus has been disputed; while long considered a nothrotheriid, one 2017 analysis moves it to Megatheriidae, while another retains it in a basal position within Nothrotheriidae.