The viscacha is another descendant of the first mass placental migration from North America which invaded grasslands and forests of South America. This invasion included some strange herbivores, most of which are now extinct. Which the separation of South from North America some of herbivores evolved to great sizes and included an animal that resembled a camel (Alticamelus) but stood over 3 metres tall. Another called the Ground Sloth, Megatherium a relation of the sloth, was 7 metres tall and lumbered across the ground, feeding on bushes and trees.
When the Panama bridge was re-established for a second time, creatures from the north again invaded South America many of these animals such as the giant camel and the sloth died out. In Patagonia, at the southernmost tip of the continent, the remains of a ground sloth were found. The cold temperatures had virtually freeze-dried the large bones and shaggy coated hide of this animal. Grass stems in the dung left by the animal appeared to have clean edges as if they had been cut by artificial means. This evidence has given rise to the hypothesis that the prehistoric Indians kept these animals in caves and feed them bales of grass.