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The oligocene epoch occured approximately 38 million years ago.
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Early forms of Amphicyonids (large terrestrial carnivores), canidaes (from the dog family), camels, tayassuidae (pigs), anthracotheres (hippos), and caprimulgiformes (birds that have wide mouths for catching insects) started to appear
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Grasses and composites (things made from several parts or elements) started to grow on a global scale. Also humid forests were becoming more common in the southern parts in
South America. -
On land, mammals such as horses, deer, camel, elephants, cats, dogs, and primates began to appear, except in Australia. The
continuation of land mammal migration between Asia and North America was responsible for the distrubution of several new continents. -
In North America, the cricetids (voles and hamsters) first appeared while the mesothermal dicotyledons (a group of flowering plants) went extinct.
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The bulk feeding in open grasslands and savannas resulted in increase of general herbivore size. For example unugulates (animals with hoovese) continued to grow in size
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During this epoch, the plate tectonics were close to what our plates look like present day. The Indian plate was still crashing into the Eurasia plate, so the Himalayas were experiencing constant uplifting.
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Miocene Epoch spanned from 5.3 million years ago to 23.03 million years ago.
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*20 million years ago
This event, along with the appearance of grasslands is one of the most important events that occured during the Miocene. This event caused new species to appear and evolve.
Kelp forests and grasslands appeared during this Epoch due to a change of cooling climate. These two biomes supported a majority of the life during this time period. -
After mountain ranges appeared in western United States, this changed the climate, causing grasslands to appear. While forest ecosystems decreased, grasslands spread. Fibory, fire-proof grasses grew in grasslands, so many of the animals were grass grazers.There were lots of wildflowers in the grasslands such as thistles, which still exist today.
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Due to the increase of grasslands, prehistoric horses evolved to something close to their current form.
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Pliocene environments were generally cooler and drier, as revealed by the remains of plants and trees, but research indicates that around 3–3.5 million years ago may have been a relatively warm period, at least in the North Atlantic. Older groups of animals became extinct throughout the preceding Miocene Epoch.
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A mass extinction during the Miocene epoch occurred in the middle of the miocene epoch. Many herbivores and grass grazers became extinct. Scientists believe that global cooling and changes in climate damaged ecosystems, which triggered mass extinction.
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Scientists have called the Miocene Epoch the golden age of apes and hominids. During this Epoch, evolving hominids roamed the Earth. The remains of these hominids give us insight and dating to the evolution of humans!
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The Rhamposuchus was traditionally thought of as one of the largest crocodiles that ever roamed the Earth. It lived in the swamps of India during the late Miosene Epoch. Recently after further research, the Rhamposuchus is estimated to be about 8-11 meters in length and 2-3 tons in weight. It was a dangerous predator that had a pointed snout to help catch prey.
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Chimpanzees branched off from hominids 6 million years ago. Chimpanzees are humans' closest relatives, so this event st arted chimps' own path towards evolution of humans. 94% of chimp's DNA matches those of humans.
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By the time the Miocene epoch was closing, almost all of the modern species of whales were swimmng in the oceans, a large variety of brids roamed the skies of Europe, and the first walruses were living as well. The miocene epoch had modernly developed animals, as well as evolving animals too.
*Planktons and mollusks evolved and diversified during this epoch. -
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Up to 30% of the Earth's surface was glaciated during the Pleistocene. Large portions of Europe, North America including Greenland, South America, all of Antarctica, and small sections of Asia were entirely covered by ice. Because so much water was taken up as ice, global sea level dropped approximately 140 meters.
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The creation of a land bridge abled species to migrate between the two continents. This led to a migration of armadillo, ground sloth, opossum, and porcupines from South to North America and an invasion of dogs, cats, bears and horses in the opposite continents.
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This long term cooling, started in the Eocene and continued up to the ice ages of the Pleistocene. During the Pliocene, large polar ice caps started to form and Antarctica became the frozen continent that it is today.
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Alligators and crocodiles died out in Europe as the climate cooled. Venomous snakes continued to increase as more rodents and birds evolved. Rattlesnakes first appeared in the Pliocene.
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The cooling and drying of the Pliocene formed grasslands and savannas.The Mediterranean Sea dried up completely and remained plains and grasslands for the next several million years. The change in vegetation was a major factor. Long-legged grazers came to live in these areas.
Grazers became larger and developed larger teeth suitable for a diet of grass. Also, longer legs they developed abled them to walk longer distances to new feeding grounds and to detect and escape predators. -
In 2002, Narciso Benítez, calculated that roughly 2 million years ago, around the end of the Pliocene epoch, a group of bright O and B stars called the Scorpius-Centaurus OB passed within 130 light-years of Earth and that one or more supernova explosions gave rise to a feature known as the Local Bubble. A close explosion could have damaged the Earth's ozone layer and caused the extinction of some ocean life.
