Representatives of modern mammals become the dominant vertebrate life form, including horses, pigs, true carnivores, rhinoceroses, elephants, and camels. Oreodonts diversify in North America. Early primates appear in North America, and early apes appear in Egypt. Many archaic mammals become extinct. The world's oceans teem with more diverse vertebrate life.
Grasslands expand, and forest regions diminish.
Miocene Epoch 24-5 million years ago Modern ocean currents are essentially established. A drop in sea level isolates and dries up the Mediterranean Sea, leaving evaporite deposits on its floor. The climate is generally cooler than the Oligocene Epoch. A cold transantarctic ocean current isolates the waters around Antarctica, and the continent becomes permanently frozen. Mammal forms are essentially modern, and almost half of modern placental mammal families are present.