![]() ![]() Grasslands and savannahs continued to be commonplace as shown in the mural above emphasizing common Pliocene American mammals. Marine and freshwater aquatic Pliocene fossils are now numerous around the globe. ![]() Famous hominid fossils such as "Lucy" a female Australopithecus aferensis and footprints from a pair of hominids alive 3Ma have been found in Pliocene deposits in Africa. In Africa early hominids appear for the first time in the fossil record. Bringing the two continents together also stopped the exchange between the Caribbean and the Pacific allowing these faunal provinces to evolve apart. Many of the South American species were replaced by northern species and eventually went extinct. Also during the Pliocene the Panamanian bridge was formed between North and South America allowing for the migration of animals both north and south in what is known as the “Great American Faunal Interchange.” Giant ground sloths, armadillos, and marsupials among others came north, while cats, dogs, bears, camels, and others went south. When the barrier on the western end was breached it refilled catastrophically from the Atlantic ocean. The collisions of the African and Eurasian continents during the Miocene had closed the Mediterranean basin both in the east and at the Straits of Gibraltar resulting in the basin drying up and converting to grasslands. Finally, on the right of this panel is a group of the small camelid Stenomylus.** Pliocene Epoch (5.332–2.588 Ma)Ī dramatic event at the beginning of the Pliocene was the catastrophic filling of the Mediterranean Sea. A group of semiaquatic Promerycochoerus are in the background and behind them a Daeodon, a large (12 ft long) pig-like scavenger or predator. Next to them in the foreground is a herd of extinct horses, Parahippus, that was evolving from a browsing habit to a grazing (eating grass) one. In front of them are a group of ruminant oreodonts ( Merychyus). On the far left are the giant (8' at the shoulder) perrisodactyl Moropus, a clawed herbivore related to horses, confronting Daphoenodon dogs. The mural above emphasizes the variety of mammals that evolved to occupy the grasslands and savannahs of North America in the Miocene epoch. The once great Tethys ocean was reduced to the Mediterranean Sea and closed at both ends, bringing the circumglobal circulation of warm waters to an end. Marine invertebrates were similar to today, in fact half of the species are unchanged.The Miocene began with a short warming, followed by a return to the general Cenozoic cooling trend. Non-mammalian predators included marine crocodiles and the largest known shark, Carcharodon megalodon. ![]() The new circulation patterns in turn lead to the evolution and spread of diverse marine mammals including a variety of toothed and baleen whales, sea lions, seals, walruses and sea cows. Ocean circulations changed to form large gyres (circular patterns) in both the Northern and Southern hemispheres. In the oceans the first known kelp forests appeared. Horses moved from browsing in forests and meadows to grazing (eating grass) in grasslands. Wide expanses of grasslands formed across the Northern Hemisphere and supported a variety of new types of mammals. The Miocene comprised most of the Neogene Period making it the second longest Epoch of the Cenozoic Era. The dramatic cooling phases of the Neogene lead to more distinctive latitudinal biotic zones. The Neogene saw a gradual closing of the Tethys Sea as the continents moved into their modern positions. Additional information about the mammals of these epochs can be found in our Prehistoric Mammals of the Cenozoic exhibits. More modern mammals evolved as grasslands became widespread and the climate cooled and dried. Complex patterns of mammalian evolution resulted from changing climates and continental separations. Whales diversified in the seas, and sharks reached their largest size during the Miocene. New food sources and niches on the grasslands and savannahs fostered further evolution of mammals and birds. The Neogene Period started with the replacement of vast areas of forest by grasslands and savannahs. This display includes the Miocene through the Pleistocene Epochs of the Neogene and Quaternary Periods. Though traditionally the Holocene is treated separately, it may in fact just be the latest interglacial of the Pleistocene. Both the Pleistocene and the Holocene are included in the Quaternary Period. It is followed by the current epoch, the Holocene, beginning eleven thousand five hundred years ago are now (2022). The Pleistocene (also known as the "Ice age"), occurred 2.58 mya and ended 11.7000 years ago. The Neogene* encompasses two epochs, beginning with the Miocene (23.03-5.33 Mya) and followed by the Pliocene (5.33-2.58 Mya).
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