Listen to Carboniferous and read Wikipedia articles about the Carboniferous period of earth's history. The planet's lungs had exhaled over the millennia and there was 150% of our oxygen, 300% of our carbon dioxide, in the air. Land was choked with impossibly thick forests, dragonflies the size of hawks, and hundred mile thunderstorms to rival those on Venus. There was enough oxygen in the air that lightning bolts would cause the air to
explode when it struck. The oceans were inhabited by aquatic scorpions nearly 3 feet long. The planet was owned by spineless creatures sheathed in thick shells. Amphibians shaped like (and acting like) crocodiles ambushed dog-sized insects on the shoreline. Millipedes were the size and weight of a car. This album is the sound of a lost world, filled with completely alien creatures.
http://en.wikipedia.org/wiki/Carboniferous