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Cambrian period |
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Cambrian periodPeriod of geological time roughly 570-510 million years ago; the first period of the Palaeozoic Era. All invertebrate animal life appeared, and marine algae were widespread. The Cambrian Explosion 530-520 million years ago saw the first appearance in the fossil record of modern animal phyla; the earliest fossils with hard shells, such as trilobites, date from this period. The name comes from Cambria, the medieval Latin name for Wales, where Cambrian rocks are typically exposed and were first described. |
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The rocks bearing the fossils were deposited on an ocean bottom about 520 million years ago during the Cambrian period. But for half a billion years, these cryptic organisms presumably were slowly evolving, diverging into different lineages and finally becoming big and complex enough to leave a profusion of fossils, beginning about 565 million years ago in the late Vendian geological period and extending into the Cambrian period. Evolution's Big Bang took place beginning 543 million years ago, in the Cambrian period. |
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Cambrian period
