Fauna and flora from each of the twelve periods of the Phanerozoic. From top left: Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian, Triassic, Jurassic, Cretaceous, Paleogene, Neogene, and Quaternary species.
Name formalityFormal
Usage information
Celestial bodyEarth
Regional usageGlobal (ICS)
Time scale(s) usedICS Time Scale
Chronological unitEon
Stratigraphic unitEonothem
First proposed byGeorge Halcott Chadwick, 1930
Time span formalityFormal
Lower boundary definitionAppearance of the Ichnofossil Treptichnus pedum
Lower boundary GSSPFortune Head section, Newfoundland, Canada
47°04′34″N 55°49′52″W / 47.0762°N 55.8310°W / 47.0762; -55.8310
Lower GSSP ratified1992
Upper boundary definitionN/A
Upper boundary GSSPN/A
Upper GSSP ratifiedN/A

The Phanerozoic[4] is the current and the latest of the four geologic eons in the Earth's geologic time scale, covering the time period from 538.8 million years ago to the present.[5] It is the eon during which abundant animal and plant life has proliferated, diversified and colonized various niches on the Earth's surface, beginning with the Cambrian period when animals first developed hard shells that can be clearly preserved in the fossil record. The time before the Phanerozoic, collectively called the Precambrian, is now divided into the Hadean, Archaean and Proterozoic eons.

The time span of the Phanerozoic starts with the sudden appearance of fossilised evidence of a number of animal phyla; the evolution of those phyla into diverse forms; the evolution of plants; the evolution of fish, arthropods and molluscs; the terrestrial colonization and evolution of insects, chelicerates, myriapods and tetrapods; and the development of modern fauna dominated by vascular plants. During this time span, tectonic forces which move the continents had collected them into a single landmass known as Pangaea (the most recent supercontinent), which then separated into the current continental landmasses.

  1. ^ "Phanerozoic". Lexico UK English Dictionary. Oxford University Press. Archived from the original on 6 August 2020.
  2. ^ "Phanerozoic". Merriam-Webster Dictionary.
  3. ^ "Phanerozoic". Unabridged (Online). n.d.
  4. ^ There are several ways of pronouncing Phanerozoic, including /ˌfænərəˈz.ɪk, ˌfænrə-, -r-/ FAN-ər-ə-ZOH-ik, FAN-rə-, -⁠roh-.[1][2][3]
  5. ^ "Stratigraphic Chart 2022" (PDF). International Stratigraphic Commission. February 2022. Retrieved 20 April 2022.

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