| Paleozoic | ||||||
|---|---|---|---|---|---|---|
| Chronology | ||||||
| ||||||
| Etymology | ||||||
| Name formality | Formal | |||||
| Alternate spelling(s) | Palaeozoic | |||||
| Usage information | ||||||
| Celestial body | Earth | |||||
| Regional usage | Global (ICS) | |||||
| Time scale(s) used | ICS Time Scale | |||||
| Definition | ||||||
| Chronological unit | Era | |||||
| Stratigraphic unit | Erathem | |||||
| Lower boundary definition | Appearance of the Ichnofossil Treptichnus pedum | |||||
| Lower boundary GSSP | Fortune Head section, Newfoundland, Canada 47°04′34″N 55°49′52″W / 47.0762°N 55.8310°W | |||||
| Lower GSSP ratified | 1992 | |||||
| Upper boundary definition | First appearance of the Conodont Hindeodus parvus. | |||||
| Upper boundary GSSP | Meishan, Zhejiang, China 31°04′47″N 119°42′21″E / 31.0798°N 119.7058°E | |||||
| Upper GSSP ratified | 2001 | |||||
The Paleozoic (/ˌpæli.əˈzoʊ.ɪk, -i.oʊ-, ˌpeɪ-/ PAL-ee-ə-ZOH-ik, -ee-oh-, PAY-;[1] or Palaeozoic) Era is the first of three geological eras of the Phanerozoic Eon. Beginning 538.8 million years ago (Ma), it succeeds the Neoproterozoic (the last era of the Proterozoic Eon) and ends 251.9 Ma at the start of the Mesozoic Era.[2] The Paleozoic is subdivided into six geologic periods (from oldest to youngest), Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian. Some geological timescales divide the Paleozoic informally into early and late sub-eras: the Early Paleozoic consisting of the Cambrian, Ordovician and Silurian; the Late Paleozoic consisting of the Devonian, Carboniferous and Permian.[3]
The name Paleozoic was first used by Adam Sedgwick (1785–1873) in 1838[4] to describe the Cambrian and Ordovician periods. It was redefined by John Phillips (1800–1874) in 1840 to cover the Cambrian to Permian periods.[5] It is derived from the Greek palaiós (παλαιός, "old") and zōḗ (ζωή, "life") meaning "ancient life".[6]
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. Arthropods, molluscs, fish, amphibians, reptiles, and synapsids all evolved during the Paleozoic. Life began in the ocean but eventually transitioned onto land, and by the late Paleozoic, great forests of primitive plants covered the continents, many of which formed the coal beds of Europe and eastern North America. Towards the end of the era, large, sophisticated synapsids and diapsids were dominant and the first modern plants (conifers) appeared.
The Paleozoic Era ended with the largest extinction event of the Phanerozoic Eon,[a] the Permian–Triassic extinction event. The effects of this catastrophe were so devastating that it took life on land 30 million years into the Mesozoic Era to recover.[7] Recovery of life in the sea may have been much faster.[8]
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