In geologic time, the Paleozoic Era, the first era in the Phanerozoic Eon, covers the time between roughly 544 million years ago (mya) and until 245 mya.

The Paleozoic Era spans six geologic time periods including the Cambrian Period (544 to 500 mya); Ordovician Period (500 mya to 440 mya); Silurian (440 mya to 410 mya); Devonian (410 mya to 360 mya); and the Carboniferous Period (360 mya to 286 mya) (in many modern geological texts, especially those in the United States, the time of Carboniferous Period is covered by two alternate geologic periods, the Mississippian Period [360 mya to 325 mya] and the Pennsylvanian Period [325 mya to 286 mya]. The final geologic time period in the Paleozoic Era is the Permian Period (286 mya to 245 mya).

The onset of the Paleozoic Era is marked by the "Cambrian explosion," the sudden appearance of numerous fossils. Although life certainly started in Precambrian time, The start of the Paleozoic Era marks the point at...