[1] In a classical view, based on skeletal anatomical studies, the Mylodontoidea in turn represent one of the two major evolutionary lineages of sloths, along with the Megatherioidea.

Prominent features are found in their high-crowned teeth, which deviate from those of the Megatherioidea with a rather flat (lobate) occlusal surface.

[12] Numerous other subfamilies have been established in the past, including, for example, the Nematheriinae for representatives from the Lower Miocene or the Octomylodontinae for all basal forms.

In principle, a revision is urged for the entire family, since numerous of the higher taxonomic units do not have a formal diagnosis.

[12] Urumacotherium Pseudoprepotherium Paroctodontotherium Octodontotherium Brievabradys Lestodon Bolivartherium Thinobadistes Sphenotherus Lestobradys Pleurolestodon Glossotheridium Simomylodon Kiyumylodon Mylodon Paramylodon Glossotherium U. campbelli was a specialist folivore and frugivore, as evidenced by its narrow muzzle and its polished tooth surfaces with few coarse scars.