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The Cambrian (/ ˈ k æ m b r i. ə n, ˈ k eɪ m-/ KAM-bree-ən, KAYM-) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. [5] The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordovician Period 486.85 Ma.
The Cambrian explosion (also known as Cambrian radiation [1] or Cambrian diversification) is an interval of time beginning approximately in the Cambrian period of the early Paleozoic, when a sudden radiation of complex life occurred and practically all major animal phyla started appearing in the fossil record.
Many modern mammal groups begin to appear: first glyptodonts, ground sloths, canids, peccaries, and the first eagles and hawks. Diversity in toothed and baleen whales. 33 Ma Evolution of the thylacinid marsupials . 30 Ma First balanids and eucalypts, extinction of embrithopod and brontothere mammals, earliest pigs and cats. 28 Ma
Cambrian: c. 538.8 Ma: Latin Cambria: Wales: ref. to the place in Great Britain where Cambrian rocks are best exposed Ordovician: c. 486.85 Ma: Celtic Ordovices: Tribe in north Wales, where the rocks were first identified Silurian: c. 443.1 Ma: Ctc. Silures: Tribe in south Wales, where the rocks were first identified Devonian: c. 419.62 Ma: Devon
Complex life, including vertebrates, begin to dominate Earth's ocean in a process known as the Cambrian explosion. Pangaea forms and later dissolves into Laurasia and Gondwana , which in turn dissolve into the current continents.
An early stem-primate, Plesiadapis, still had claws and eyes on the side of the head, making it faster on the ground than in the trees, but it began to spend long times on lower branches, feeding on fruits and leaves. The Plesiadapiformes very likely contain the ancestor species of all primates. [24]
The Cambrian is the first period of the Paleozoic Era and ran from 539 million to 485 million years ago. The Cambrian sparked a rapid expansion in the diversity of animals, in an event known as the Cambrian explosion , during which the greatest number of animal body plans evolved in a single period in the history of Earth.
The sequence dates from the late Proterozoic through the early Ordovician periods, though the marine transgression did not begin in earnest until the middle Cambrian. [2] It is one of the most striking cratonic sequences in the geological record, spreading sheets of sandstone across basement rock deep into the interiors of many continents.