Geologists divide Earth’s 4.5 billion year history into several long eras, each of which is subdivided into briefer periods. The Pliocene, 5.6-2.5 million years ago, is the epoch, in the Neogene Period, just prior to the time of the ice ages that we inhabit, the Pleistocene.
Earth was hotter by several degrees Celcius and wetter during the Pliocene. The atmosphere contained about the same amount of carbon dioxide as today. During the late Pliocene North America became linked to South America by the Isthmus of Panama. Because of the warmer wetter climate, less of Africa was savannah or desert. Pliocene fauna were slightly more primitive, but not dramatically different from animals of the our Pleistocene age. Elephant-like mastodons grazed vegetation in North America (and continued to do so until about 12 thousand years ago, when they were hunted to extinction).
Because the Pliocene was hotter than today, researchers believe that ice sheets were smaller and sea level was higher. Much research supports this belief. But studies conflict over how much higher the sea level was. The broad range of estimates goes from about 5 meters to about 35 meters above present-day sea level.