After the Paleocene Epoch there is the second phase of the Paleogene or Tertiary Period called the Eocene Epoch. The Eocene was marked by the dominance of angiosperms and the continuation of mammals due to radiation. The Eocene epoch lasted from 57 to 35 million years ago. Being the second phase of Earth in which there were no dinosaurs, meant that there was plenty of room for other, previously less competitive species to thrive. This epoch began as a result of the escape of methane gas from the ocean floor during the Paleocene epoch. Due to the extinction of animals during the late Paleocene epoch, other organisms in the Eocene epoch had to regroup to ensure they were not the next organisms to go extinct. Fossils from the era are widely distributed, demonstrating the range of organisms found during the time. The animals that lived during the Eocene Epoch were the result of the extinction of their predators and also the evolution of species to adapt to changes in the environment. For example, radiation released in the Northern Hemisphere caused not only the appearance of more mammals, but also their increase in size. Average mammals now weighed about twenty pounds according to their fossils. Furthermore, a change in temperature during the later part of the Eocene caused other animals, not just mammals, to increase in size in response to the cooler climate. Not only have the animals gotten bigger, but the temperature change has also changed the habitats from lots of forests to more grasslands. In addition to the temperature change, most land bridges between continents remained so that animals could move freely between most continents, excluding Australia. New marine animals include molluscs and the first... middle of paper... tectonic plates that caused fault lines to shift. This shift had a huge effect in changing ocean water currents and perhaps even influencing atmospheric temperatures. The Eocene epoch ended approximately 35 million years ago allowing the beginning of the third epoch of the Cenozoic era, the Oligocene. The end of the Eocene can be considered a fact of the plate movement observed above. Not only did the plates shift, but they also caused a sharp change in the temperatures observed in the atmosphere. The sudden drop in average temperatures caused the general climate to abandon the humid and subtropical level and become very dry. The polar ice caps returned to the Earth's North and South Poles. This form of cooling has affected many organisms, causing their extinction, but also allowing the creation of different types of habitats, such as woods..