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The Cambrian Period (pronunciation: // or //) was the first geological period of the Paleozoic Era, of the Phanerozoic Eon. The Cambrian lasted 55.6 million years from the end of the preceding Ediacaran Period 541 million years ago (mya) to the beginning of the Ordovician Period 485.4 mya. Its subdivisions, and its base, are somewhat in flux. The period was established (as “Cambrian series”) by Adam Sedgwick, who named it after Cambria, the Latinised form of Cymru, the Welsh name for Wales, where Britain's Cambrian rocks are best exposed. The Cambrian is unique in its unusually high proportion of lagerstätte sedimentary deposits, sites of exceptional preservation where "soft" parts of organisms are preserved as well as their more resistant shells. As a result, our understanding of the Cambrian biology surpasses that of some later periods.
The Cambrian marked a profound change in life on Earth; prior to the Cambrian, the majority of living organisms on the whole were small, unicellular and simple; the Precambrian Charnia being exceptional. Complex, multicellular organisms gradually became more common in the millions of years immediately preceding the Cambrian, but it was not until this period that mineralized—hence readily fossilized—organisms became common. The rapid diversification of lifeforms in the Cambrian, known as the Cambrian explosion, produced the first representatives of all modern animal phyla. Phylogenetic analysis has supported the view that during the Cambrian radiation, metazoa (animals) evolved monophyletically from a single common ancestor: flagellated colonial protists similar to modern choanoflagellates.
541–485.4 million years ago
|Mean atmospheric O
2 content over period duration
|c. 12.5 vol %
(63 % of modern level)
|Mean atmospheric CO
2 content over period duration
|c. 4500 ppm
(16 times pre-industrial level)
|Mean surface temperature over period duration||c. 21 °C
(7 °C above modern level)
|Sea level (above present day)||Rising steadily from 30m to 90m|
|Furongian||Ibexian (part)||Ayusokkanian||Datsonian||Dolgellian (Trempealeauan, Fengshanian)|
|Sunwaptan||Sakian||Iverian||Ffestiniogian (Franconian, Changshanian)|
|Cambrian Series 3||Maozhangian||Mayan||Boomerangian|
|Cambrian Series 2||Longwangmioan||Toyonian||Lenian|
Trilobites were very common during this time
Pikaia was an early chordate from the Middle Cambrian
Opabinia was a creature with an unusual body plan; it was probably related to arthropods
Protichnites were the trackways of arthropods that walked Cambrian beaches.
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