<Tr> <Td_colspan="2"> Key events in the Paleozoic - 550---- - 500---- - 450---- - 400---- - 350---- - 300---- - 250---- Neoproterozoic Mesozoic Cambrian Ordovician Silurian Devonian Carboniferous Permian l o z o i Phanerozoic Eon Proterozoic Eon An approximate timescale of key Paleozoic events . Axis scale: millions of years ago . </Td> </Tr> <P> The Paleozoic (or Palaeozoic) Era (/ ˌpeɪliəˈzoʊɪk, ˌpæ - /; from the Greek palaios (παλαιός), "old" and zoe (ζωή), "life", meaning "ancient life") is the earliest of three geologic eras of the Phanerozoic Eon . It is the longest of the Phanerozoic eras, lasting from 541 to 251.902 million years ago, and is subdivided into six geologic periods (from oldest to youngest): the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian . The Paleozoic comes after the Neoproterozoic Era of the Proterozoic Eon and is followed by the Mesozoic Era . </P> <P> 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 . Fish, arthropods, amphibians, anapsids, synapsids, euryapsids, and diapsids all evolved during the Paleozoic . Life began in the ocean but eventually transitioned onto land, and by the late Paleozoic, it was dominated by various forms of organisms . 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 diapsids and synapsids were dominant and the first modern plants (conifers) appeared . </P> <P> The Paleozoic Era ended with the largest extinction event in the history of Earth, 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 . Recovery of life in the sea may have been much faster . </P>

Diapsids dominated the terrestrial landscape for the first time following which event