Harlan’s Ground Sloth (Paramylodon harlani)

Harlan's Ground Sloth Illustration William Stout

From La Brea Tar Pits Website:

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 skeletal structure of these ground sloths indicates that the animals were massive. Their thick bones and even thicker joints (especially those on the hind legs) gave their appendages tremendous power that combined with their size and fearsome claws, provided a formidable defense against predators.

These ground sloths had a massive skeletal structure. Their thick joints and bones gave them tremendous power in their arms and legs, as well as their long tail. Combined with their huge size and massive claws, the strength of this creature provided a strong defense against predators. On hind legs, Paramylodon was roughly the same size as the Giant Short-Faced Bear, and could most likely wrestle one to the ground in a fight for it’s life.

La Brea Tar Pits
Illinois State Museum


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