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(began 37-34 million years ago)

Scientists are now conducting research that may move the Eocene/Oligocene boundary to 34 million years ago. Such changes in geological time divisions may be an issue of debate for generations to come, leading to some ambiguity. The Oligocene Epoch was a time of transition between the earlier and later parts of the Cenozoic Era. The climate, which had been warm and moist, became cooler and direr. Subtropical forests began to give way to more temperate forests. Late in the Oligocene, savannas (grasslands broken by scattered woodlands) appeared. Influenced by these changes, mammals, insects, and other animals continued the trend toward specialization. Some adapted to the diminishing forests by becoming grazers. Early types of mammals continued to die out, as more modern groups (dogs, cats, horses, pigs, camels, and rodents) rose to new prominence.


Tsetse Fly from the Oligocene

Tsetse flies occur today in tropical Africa and as fossils in the Florissant formation.
Florissant Fossil Beds NM

Oligocene Butterfly

Butterflies and many other insect groups evolved with the increasing numbers and variety of flowering plants and became important agents of pollination.
Florissant Fossil Beds NM

Redwood Tree

Groves of giant redwood trees were found throughout western North America. Changes in climate were responsible for the shrinking range of the redwood forests.
Florissant Fossil Beds NM

Oligocene Oreodont

Oreodonts, a group of sheep-like animals, were successful in the Eocene and Oligocene but by the end of the Miocene had completely died out.
Badlands NP

continue to Miocene
updated on 01/04/2005  I   http://www.nature.nps.gov/geology/parks/Oligocene.cfm   I  Email: Webmaster
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