Not so very long ago, giant ground sloths trundled through the forests and over the grasslands of North America. Like the sabercats and mammoths of their time, the shaggy beasts and their armored glyptodont cousins were part of the recently-lost Pleisotcene megafauna. Yet the sloths and their kin had a very different backstory from the rest of the characteristic, charismatic megamammals that inhabited Ice Age North America.

Whereas mammoths and sabercats migrated in from Eurasia, and horses and camels evolved in North America itself, the sloths and glyptodonts were southern pioneers whose lineages had evolved in the “splendid isolation”, as paleontologist George Gaylord Simpson called it, of South American before the Isthmus of Panama closed the gap between the Americas around