Extinct Ground Sloths (Paramylodon harlani, Nothrotheriops shastensis, and Megalonyx jeffersoni) Fact Sheet: Reproduction & Development

Isotope studies of elements present fossil bones and tusks in microscopic quantities give information about timing of reproductive stress, and timing of nursing. Clues to stages of development come from tooth replacement patterns and closure of sutures in skull and limb bones.

•  A fossil sloth related to the Shasta ground sloth, found in a cave in Brazil, had a single foetus associated with the adult. (Auler & Smart 1999)
• Shasta ground sloth juveniles found in many caves in southwestern U.S. (Hill & Gillette 1985)
• A Megalonyx jeffersoni adult found in Iowa (Brenzel & Semken 2006) had two associated juveniles of different ages, suggesting extended parental care.

• Ground sloths juveniles would have been vulnerable to the large cat predators (Smilodon, Homotherium, Panthera atrox) and perhaps Dire Wolves
• Not known why ground sloths became extinct, but some researchers suggest humans had something to do with it. (Steadman et al 2007)

Auler & Smart (1999)
Brenzel & Semken (2006)
Hill & Gillette (1985)