Eocene

The Eocene epoch (56-34 mya) is a major division of the geologic timescale and the second epoch of the Palaeogene period in the Cenozoic era. The Eocene spans the time from the end of the Paleocene epoch to the beginning of the Oligocene epoch. The start of the Eocene is marked by the emergence of the first modern mammals. The end is set at a major extinction event that may be related to the impact of one or more large bolides in Siberia and in what is now Chesapeake Bay. Still, as with other other geologic periods, the strata that define the start and end of the epoch are well identified, but their exact dates are slightly uncertain.

Eocene fauna

The oldest known fossils of most of the modern mammal orders appear within a brief period during the early Eocene. At the beginning of the Eocene, several new mammal groups arrived in North America. These modern mammals, like artiodactyls, perissodactyls and primates, had features like long, thin legs, feet and hands capable of grasping, as well as differentiated teeth adapted for chewing. Dwarf forms reigned. All the members of the new mammal orders were small, under 10 kg; based on comparisons of tooth size, Eocene mammals were only 60 per cent of the size of the primitive Paleocene mammals that had preceded them. They were also smaller than the mammals that followed them. It is assumed that the hot Eocene temperatures favored smaller animals that were better able to manage heat.

Related Topics:
Fossil - Artiodactyl - Perissodactyls - Primate - Teeth - Paleocene

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Both groups of modern ungulates (hoofed animals) became prevalent due to a major radiation between Europe and North America; along with carnivourous ungulates like Mesonyx. Early forms of many other modern mammalian orders appeared, including bats, proboscidians, primates, rodents and marsupials. Older primitive forms of mammals declined in variety and importance. Important Eocene land fauna fossil remains have been found in western North America, Europe, Patagonia, Egypt and South-East Asia. Marine fauna are best known from South Asia and the southeast United States.

Related Topics:
Ungulate - Mesonyx - Bat - Proboscidian - Primate - Rodent - Marsupials - Patagonia - Egypt - South-East Asia - South Asia - United States

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During the Eocene plants and marine faunas became quite modern. Many modern bird orders first appear in the Eocene.

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