Scelidotheriidae

Scelidotheriidae is a family of extinct ground sloths within the order Pilosa, suborder Folivora and superfamily Mylodontoidea, related to the other extinct mylodontoid family, Mylodontidae, as well as to the living two-toed sloth family Choloepodidae. The only other extant family of the suborder Folivora is the distantly related Bradypodidae. Erected as the family Scelidotheriidae by Ameghino in 1889, the taxon was demoted to a subfamily of Mylodontidae by Gaudin in 1995.^[1][2] However, recent collagen sequence data indicates the group is less closely related to Mylodon and Lestodon than Choloepus is, and thus it has been elevated back to full family status by Presslee et al. (2019).^[3]

Scelidotheriidae Temporal range: Late Oligocene-Late Pleistocene (Deseadan-Lujanian) ~29–0.009 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Scelidotherium leptocephalum in Paris
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Pilosa
Superfamily:	Mylodontoidea
Family:	†Scelidotheriidae Ameghino 1889
Genera
†Analcitherium †Catonyx †Chubutherium †Nematherium †Neonematherium †Proscelidodon †Scelidodon †Scelidotheridium †Scelidotheriops †Scelidotherium †Sibyllotherium †Valgipes

Taxonomy

Together with Mylodontidae, and the two-toed sloths, the scelidotheriids form the superfamily Mylodontoidea. Chubutherium is an ancestral and very plesiomorphic member of this family and does not belong to the main group of closely related genera.

Phylogeny

The following sloth family phylogenetic tree is based on collagen and mitochondrial DNA sequence data (see Fig. 4 of Presslee et al., 2019).^[3]

Folivora	† Megalocnidae (Caribbean sloths) Mylodontoidea † Scelidotheriidae † Scelidodon sp. † Scelidotherium sp. † Mylodontidae † Lestodon armatus † Paramylodon harlani † Glossotherium robustus † Mylodon darwinii Choloepodidae (two-toed sloths) Choloepus didactylus Choloepus hoffmanni Megatherioidea † Megalonychidae    Bradypodidae (three-toed sloths) † Nothrotheriidae † Megatheriidae

Below is a more detailed cladogram of the Scelidotheriidae, based on the work of Nieto et al. 2020.^[4]

Scelidotheriinae	Sibyllotherium guenguelianum Neonematherium flabellatum Scelidotherium Proscelidodon gracillimus Proscelidodon patrius Proscelidodon rothi Valgipes bucklandi Catonyx cuvieri Catonyx tarijensis Catonyx chiliense