The megafaunas inhabiting the earth after the great cataclysmic event that nearly wiped out everything.
towering jungles and various other biomes began refilling the earth after the apocalypse, biomes that are several magnitudes larger and more diverse than the previous ones from the old world, elevating huge amounts of oxygen into the atmosphere, even higher than the carboniferous period over 300 million years ago.

most of the faunas living in this age look as if they have reverted back to their old cretaceous ancestors, save for the giant arthropods roaming the forest floors and gigantic chasms.