Harlan's Ground Sloth

Shasta Ground Sloth

Evolving from the tree sloths in South America, ground sloths are very distantly related to anteaters and armadillos. As this animal adapted from a tree dweller to being ground-based, its limbs still showed a relationship to its ancestors. Typically, ground sloths walked on the sides of their hind feet and the backs of their forefeet.

Harlan's ground sloth was the largest and most common of the ground sloths found at Rancho La Brea. It stood over six feet tall and weighed almost 3,500 pounds. This animal had flat grinding teeth that suggest a diet of grasses, but may have also fed on leaves, tree roots, and twigs. One of the most interesting features of the Harlan's ground sloth were its skin bones, or dermal ossicles. These small bones were deep under the skin around the neck, shoulders and back and may have served as armor against attacking predators. They were not connected to the main skeleton and were unique to this type of ground sloth.

The other common sloth found at Rancho La Brea is the Shasta ground sloth. It had a larger tube-shaped snout and fewer teeth than its larger relative, the Harlan's ground sloth. Recent scientific findings have suggested that the Shasta ground sloth was a browser, feeding on leaves, shrubs and tree branches.

The basic structure of a ground sloths hind (left) and front (right) limbs.

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