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 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]

Temporal range: Late Oligocene-Late Pleistocene (Deseadan-Lujanian)
~23–.011 Ma
Scelidotherium leptocephalum side.jpg
Scelidotherium leptocephalum in Paris
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Pilosa
Suborder: Folivora
Family: Scelidotheriidae
Ameghino 1889

See text


Together with Mylodontidae, the enigmatic Pseudoprepotherium, and 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.

Family †Scelidotheriidae Ameghino 1889


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


Megalocnidae (Caribbean sloths)




Bradypodidae (three-toed sloths)



Scelidotherium sp.

Scelidodon sp.

  (two-toed sloths)  

C. didactylus

C. hoffmanni


Lestodon armatus

Paramylodon harlani

Mylodon darwinii

Glossotherium robustus    



  1. ^ PaleoBiology Database: Scelidotheriinae, basic info
  2. ^ Gaudin, T. J. (1995-09-14). "The Ear Region of Edentates and the Phylogeny of the Tardigrada (Mammalia, Xenarthra)". Journal of Vertebrate Paleontology. 15 (3): 672–705. doi:10.1080/02724634.1995.10011255. JSTOR 4523658.
  3. ^ a b Presslee, S.; Slater, G. J.; Pujos, F.; Forasiepi, A. M.; Fischer, R.; Molloy, K.; Mackie, M.; Olsen, J. V.; Kramarz, A.; Taglioretti, M.; Scaglia, F.; Lezcano, M.; Lanata, J. L.; Southon, J.; Feranec, R.; Bloch, J.; Hajduk, A.; Martin, F. M.; Gismondi, R. S.; Reguero, M.; de Muizon, C.; Greenwood, A.; Chait, B. T.; Penkman, K.; Collins, M.; MacPhee, R.D.E. (2019). "Palaeoproteomics resolves sloth relationships" (PDF). Nature Ecology & Evolution. 3 (7): 1121–1130. doi:10.1038/s41559-019-0909-z. PMID 31171860. S2CID 174813630.

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