What is Eocene?
The '''Eocene''' was the second [[geology|geological]] [[Epoch (geology)|epoch]] in the [[Palaeogene]], and by far the longest.<ref>Kennet J.P. & Stott L.D. 1995. Terminal Paleocene mass extinction in the deep sea: association with global warming. Effects of past global change on life: studies in geophysics. ''National Academy of Sciences''.</ref> It began 56 [[million]] years ago, and ended 33.9 million years ago with a global warming crisis. Before the period was the [[Palaeocene]], and after the time was the [[Oligocene]], the time where [[Paraceratherium|paraceratheres]], [[Indricotherium|indricotheres]], [[Entelodon|entelodonts]], [[Hyaenodon|hyaenodonts]], [[Archaeotherium|archaeotheres]], [[Chalicotherium|chalicotheres]], [[Arsinoitherium|arsinoitheres]] and [[Cynodictis|cynodictids]] were the main animals. The Eocene, like the [[Palaeocene]] before it, had a climate much warmer than today. At the start of the Eocene, the ''Palaeocene–Eocene Thermal Maximum'' was reached. This lasted for 100,000 years, and caused a large [[List of extinction events|extinction event]]. The land was heavily [[forest]]ed, with temperate forests into [[Arctic]] and [[Antarctic]] regions. The many [[herbivorous]] mammals were [[browser]]s, not [[grazer]]s. All the members of the new mammal orders were small, under 10 kg. Eocene mammals were only 60% of the size of the primitive Palaeocene mammals that came before them. They were also smaller than the mammals that followed them. The main animals of the time included ''[[Propalaeotherium]]'', ''[[Leptictidium]]'', ''[[Ambulocetus]]'', ''[[Pristichampsus]]'', ''[[Gastornis]]'' and ''[[Hyracotherium]]''. The end of the Eocene was the beginning of the [[Oligocene]] (33.9 million years ago). Many plant and animal species went extinct. This was the [[Eocene–Oligocene extinction event]]. The extinction event was probably caused by [[meteorite]] strikes in [[Siberia]] and [[Chesapeake Bay]]. The fauna of this timeline included [[Basilosaurus|basilosaurs]], [[Arsinoitherium|arsinoithe