Home | A summary of on the Epochs of the Age of Mammals, the Cenozoic |
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I have had some difficulty remembering the epochs of the age of mammals, which makes it difficult to read the literature on that period. So I set to work to straighten the whole thing out in my mind, and now I am writing my thinking down on this page. That way both the general public and I will be able to refer to it.
The age of mammals, the cenozoic, has been split into seven epochs. Those seven epochs are as follows:
Paleocene ~65-56 Million Years AgoThe comet or meteor hit and the dinosaurs were wiped out roughly 65 million years ago. This left the relatively tiny mammals to seize the larger land niches. The mammals rapidly evolved larger sizes.It is my impression that many of the larger mammals were rather crude early drafts by evolution. Eocene ~56-34 Million Years AgoSomething made the earth much hotter for 100 thousand years at the transition between the Paleocene and Eocene. This is called the Paleocene-Eocene Thermal Maximum. Many species went extinct as a result.It is the official explanation that the heat got them. Even after the hot spell the Eocene was very warm. From the Eocene through the Pleistocene, the world generally became colder. In the tropical world of the Eocene the mammals were somewhat smaller than before or after the Eocene. The mammals were on average only 60 percent of the size of the late Paleocene mammals. The earliest fossils of most of the modern mammal orders are found in the Eocene. Oligocene ~34-23 Million Years AgoThe Oligocene began with an extinction event. The earth may have been hit by a large object.As the earth became cooler and dryer the mammals became very large. This was the era of indricotherium, the giant hornless rhino which is the largest land mammal that ever lived. It is also the era of brontotherium, the giant animal that looks like a rhino with a forked horn. This period of relatively unsophisticated giants seems to be similar to the Jurassic for the age of dinosaurs. Miocene ~23-5.3 Million Years AgoThe animals in the Miocene were quite different from the Oligocene but quite similar to those we are familiar with. The climate was cooling but still warmer than ours. Much of the Miocene was as warm as the earlier Oligocene.Pliocene ~5.3-1.8 Million Years AgoThe climate is about the same as ours, and the animals are also fairly similar. For the animals think Africa with more hair.Pleistocene ~1.8 Million Years Ago To 11 Thousand Years AgoThe Pleistocene has commonly been called the ice age. Glaciers advanced and it was very cold most of the time. But there were warmer interglacial periods, like the one we are in now.Holocene ~Last 11 thousand YearsThe Holocene is the current interglacial period. Perhaps because of man, this interglacial period has lasted longer than previous ones. Agriculture developed fairly early in the Holocene, and for about half of the Holocene there have been human civilizations and written language.One might suspect that the Pleistocene would have continued without us.
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