30 million years AP

Despite the generally positive trend of global temperature, the middle Lentocene is facing a small Ice Age: temperature has dropped, causing a significant surface decrease in forest cover. Less frost-adapted species, like the austral oak (Austriquercus sp.), are now found only in relictual habitats of North Weddell.  The sudden decrease of temperature of the middle Lentocene has caused several local extinctions: insular habitats were the most affected since their ecosystems are often miniaturized and even a little change of temperature can potentially cause their disappearance. Woodland fauna, obviously, was the most impacted community by this climatic event.
With the expansion of the Big White, the tundra biome has once again increased its surface, becoming the predominant ecosystem of the entire Antarctica.
The sea level has also decreased, facilitating the colonization of antarctic islands from the mainland. At the same time, a short-living oceanic dorsal has formed between Polarica and Marie Byrd, slowly drifting the island away from the Lorentz peninsula.

Generalized map of antarctic biomes. Due to the presence of lots of glacial valleys close to each other, Weddell and Marie Byrd islands seem more forested than in reality. The cross shows the South Pole.