Deep deep deep in space there is a type of reptilian alien that has collected the DNA of every animal and plant on planet earth. Every time that a creature goes extincted, The reptilians put a clone of that animal or plant on the planet in an environment very close to its old one. This planet is very very similar to earth but this planet is over 200 times bigger, The roam across the land, swim threw the water and roam the sky's just like they once did long ago. There is over 3000 large alien ships working to put the animals on this planet to study them and watch there evolution.
Not only have they transported extincted plants to this planet but have also replaced this new planets strange Flora with plants of earth such as, Grasses, Trees, mushrooms, shrubs, vine plants, predatory plants, ferns, conifers, and every other kind of plant on earth. Animals from every time era from earth lives on this planet at the same time, evolving into bran new forms.
This all has started ever sense the first multicellular creature evolved but has started to place them ever sense the 1600s. There are rain forest bigger then earth, lakes the size of Asia, Oceans so big that it could take hundreds of years to sail across but this planet is just the animals and plants on there own. This world is a warm in lush habitat that only is cold in the deepest part of the north and south, just like the earths north and south poles. This planet that they all live on was once a waste land of nuclear wars and death but after 10 million years of fixing the planet back to its original health, They started to bring the extincted flora and fauna to the planet.