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The Oligocene (35.4-23.3 mya)

  oligocene community
Oligocene community (Smithsonian Institution 2000)

        A period of extreme global cooling occurred at or near the Eocene-Oligocene boundary, with glaciation accompanied by worldwide regression (Prothero 1998). This cooling event strongly affected the southern hemisphere (Prothero 1998) and organisms living in high latitudes (WGBH 2001).  Global temperatures throughout the Oligocene were much cooler and had more seasonal variation than those in the Eocene, and this caused a vegetation change as the forests continued to decline and woodlands took their place (WGBH 2001). Because of the cooler, drier climate, grasslands started to appear near the end of the epoch (WGBH 2001), but these did not become widespread until the Miocene (Janis et al. 2002).

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