South America becomes an island continent
Cut off from the north, a marsupial-and-ungulate fauna evolves in isolation for 60 million years.
- When
- —
- Duration
- 10 million years
- Known to
- ± 2 million years
- Era
- Paleocene, Cenozoic
With North America separated and Antarctica still attached to its southern tip, South America becomes an isolated landmass with its own experiment running. Marsupials fill the carnivore roles, producing forms as extreme as the sabre-toothed Thylacosmilus; a suite of native ungulates unrelated to anything elsewhere fills the herbivore roles; and the xenarthrans — sloths, anteaters and armadillos — arise here and nowhere else. The isolation lasts until the Isthmus of Panama closes, and most of what it produced does not survive the reconnection.