The Paleozoic or Palaeozoic Era (from the Greek palaios (παλαιός), ""old"" and zoe (ζωή), ""life"", meaning ""ancient life"") is the earliest of three geologic eras of the Phanerozoic Eon. The Paleozoic spanned from roughly 542 to 251 ẹgbẹgbẹ̀rún ọdún sẹ́yìn (ICS, 2004), and is subdivided into six geologic periods; from oldest to youngest they are: the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian. Fish populations exploded in the Devonian. During the late Paleozoic, great forests of primitive plants throve on land forming the great coal beds of Europe and eastern North America. By the end of the era, the first large, sophisticated reptiles and the first modern plants, (conifers) had developed.