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Cambrian. g. g. FAD of the Conodont Iapetognathus fluctivagus. The Cambrian ( / ˈkæmbri.ən, ˈkeɪm -/ KAM-bree-ən, KAYM-) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. [5] The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of ...
Cambria. Cambria is a name for Wales, being the Latinised form of the Welsh name for the country, Cymru. [1] The term was not in use during the Roman period (when Wales had not come into existence as a distinct entity) or the early medieval period. After the Anglo-Saxon settlement of much of Britain, a territorial distinction developed between ...
Ordovician. Vertical axis scale: millions of years ago. The Ordovician (/ ɔːrdəˈvɪʃi.ən, - doʊ -, - ˈvɪʃən / or-də-VISH-ee-ən, -doh-, -VISH-ən) [9] is a geologic period and system, the second of six periods of the Paleozoic Era, and the second of twelve periods of the Phanerozoic Eon.
The Silurian (/ sɪˈljʊəri.ən, saɪ -/ sih-LURE-ee-ən, sy-) [8][9][10] is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at 443.8 million years ago (Mya), to the beginning of the Devonian Period, 419.2 Mya. [11] The Silurian is the third and shortest period of the Paleozoic Era, and the ...
The Paleozoic was a time of dramatic geological, climatic, and evolutionary change. The Cambrian witnessed the most rapid and widespread diversification of life in Earth's history, known as the Cambrian explosion, in which most modern phyla first appeared.
The Cambrian explosion (also known as Cambrian radiation [1] or Cambrian diversification) is an interval of time 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.
It covers the time from the appearance of free oxygen in Earth's atmosphere to just before the proliferation of complex life on the Earth during the Cambrian Explosion. The name Proterozoic combines two words of Greek origin: protero-meaning "former, earlier", and -zoic, meaning "of life". [8]
Pikaia gracilens is an extinct, primitive chordate animal known from the Middle Cambrian Burgess Shale of British Columbia.Described in 1911 by Charles Doolittle Walcott as an annelid, and in 1979 by Harry B. Whittington and Simon Conway Morris as a chordate, it became "the most famous early chordate fossil", [1] or "famously known as the earliest described Cambrian chordate". [2]