The Rise of Mammals

Whales are believed to be about 50 million years old. The toothed baleen whale was thought to be extinct in the Oligocene Epoch and believed to be living in the Miocene Epoch, the time period that came after the Oligocene period. The whales discovered by Mr. Plunkett at Lake Casitas swam through the “tail” end of the Oligocene Epoch, (25 to 23 million years ago), and continued swimming into the Miocene Epoch, (23 to 5 million years ago). These whales lived in overlapping epochs of time and underwent very specific evolutionary changes, such as the process of losing their teeth and acquiring baleens. This reveals important and crucial information about tracing the evolutionary rise of mammals and whales on earth.



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