quality:corruption, structural:reformatting, stylistic:style_transfer, linguistic:voice_change, structural:expansion
Cenozoic era before present (66–10 Ma)

During the early Paleogene, Antarctica remained connected to South America as well as to southeastern Australia. Fauna from the La Meseta Formation in the Antarctic Peninsula, dating to the Eocene, is very similar to equivalent South American faunas; with marsupials, xenarthrans, litoptern, and astrapotherian ungulates, as well as gondwanatheres and possibly meridiolestidans. Marsupials are thought to have dispersed into Australia via Antarctica by the early Eocene.

Around 53 Ma, Australia- New Guinea separated from Antarctica, opening the Tasmanian Passage. The Drake Passage opened between Antarctica and South America around 30 Ma, resulting in the creation of the Antarctic Circumpolar Current that completely isolated the continent. Models of Antarctic geography suggest that this current, as well as a feedback loop caused by lowering CO levels, caused the creation of small yet permanent polar ice caps. As CO levels declined further the ice began to spread rapidly, replacing the forests that until then had covered Antarctica. Tundra ecosystems continued to exist on Antarctica until around 14-10 million years ago, when further cooling lead to their extermination.