Megalonyx jeffersonii Desmarest, 1822

Jefferson's ground sloth



Taxonomy & Nomenclature



Conservation Status


Last record: 11,235 ± 40 14C yr BP = 13,180–13,034 cal yr BP (McDonald et al. In Press)



USA (New Mexico & Oklahoma)


Biology & Ecology










Babcock, Loren E. (2024). Nomenclatural history of Megalonyx Jefferson, 1799 (Mammalia, Xenarthra, Pilosa, Megalonychidae). ZooKeys 1195: 297-308.

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Dantas, Mário A. T., Campbell, Sean Cody and McDonald, H. Gregory. (2023). Paleoecological inferences about the Late Quaternary giant ground sloths from the Americas. Research Square preprint.

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Gillette, D. D., McDonald, H. Gregory and Hayden, M. C. (1999). Thee first record of Jefferson’s Ground Sloth, Megalonyx jeffersonii, in Utah (Pleistocene, Rancholabrean Land Mammal Age): Utah Geological Survey Miscellaneous Publication 99(1): 509-521.

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Harris, Arthur H. (1993). Quaternary vertebrates of New Mexico, pp. 179-197. In: Vertebrate Paleontology in New Mexico, New Mexico Museum of Natural History, Bulletin 2: i-vii, 1-338.

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Hoganson, John W. and McDonald, H. Gregory. (2007). First Report of Jefferson’s Ground Sloth (Megalonyx Jeffersonii) in North Dakota: Paleobiogeographical and Paleoecological Significance. Journal of Mammalogy 88(1): 73-80.

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Jefferson, Thomas. (1799). A memoir on the discovery of certain bones of a quadruped of the clawed kind in the western parts of Virginia. Transactions of the American Philosophical Society 4: 246-250.

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McDonald, H. Gregory. (1996). Biogeography and Paleoecology of Ground Sloths in California, Arizona and Nevada. SBCMA Quarterly 43(1): 61-65.

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McDonald, H. Gregory, Feranec, Robert S. and Miller, Norton. (In Press, 2018). First record of the extinct ground sloth, Megalonyx jeffersonii, (Xenarthra, Megalonychidae) from New York and contributions to its paleoecology. Quaternary International. [Abstract]

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McDonald, H.G., Miller, W.E., and Morris, T.H., 2001, Taphonomy and significance of Jefferson’s Ground Sloth (Xenarthra: Meg-alonychidae) from Utah: Western North America Naturalist, v. 61, no. 1, p. 64–77.

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McDonald, H. Gregory et al. (In Press, 2015). Youngest radiocarbon age for Jefferson's ground sloth, Megalonyx jeffersonii (Xenarthra, Megalonychidae). Quaternary Research. doi:10.1016/j.yqres.2014.11.006 [Abstract]

Mead, J. I., N. J. Czaplewski, and L. D. Agenbroad. 2005. Rancholabrean (Late Pleistocene) mammals and localities of Arizona. Pp. 139-180, in (R. D. McCord, ed.) Vertebrate Paleontology of Arizona, Mesa Southwest Museum Bulletin No. 11.

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