A time when Earth had healed itself from the ravages of the massive meteor strike. Much had changed since the time of the dinosaurs. It was far hotter now and lush tropical rainforests had sprung up on every continent from the Arctic to Antarctica. During this flowering new Eden, meteors no longer present as much of a threat. Under the forest canopies of the Eocene thrived a menagerie of weird wonderful creatures. Here, the rule of scaly reptiles is a distant memory. The animals that dominate now are covered in feathers or fur. Mammals had adapted well to the new world and there is a staggering variety of them, but they are still small, and, as before, live under shadows of bigger, deadlier animals. The dinosaurs might have been long gone, but they left the world a vicious legacy. Their direct descendants are the birds. For the first and only time in its history, birds rule the Earth. At this time in Europe's history, Germany was at the center of much volcanic activity, and whole patches of forests were riddled with geothermal springs. In places, these form seething mud pools.
In the later Eocene, the climate became cooler and dryer. It was still a hot world. However, it was drier than before. While the land once was completely covered in lush rainforests, there were now more open spaces. Freed from the constraints of living in dense forest environments, some species of mammals began to grow larger. And on the scrub plains, big was beautiful. However, these changes did not suit all species of creatures. The large killer birds were not seen at this time. Rather, they were replaced on most continents by new and terrifying mammal predators. Like the dinosaurs before them, mammals dominated the planet.
Additionally, when the dinosaurs disappeared, the gigantic marine reptiles, such as the eel-like Cymbospondylus, the large four-flippered Liopleurodon, and even the giant snake-like Mosasaurs, that once terrorized the oceans all went extinct as well. For almost 25 million years, there was nothing around to eat the sharks. However, the Eocene was also when the giant whales first evolved. Here, you can forget the giant, gentle filter feeders of the 21st Century. In prehistoric times, virtually every species of whales were killers.
The list of animals that lived during the Eocene: