The Paleozoic era has 6 periods Cambrian, Carboniferous, Devonian Ordovician, Permian and Slurian in alphabetical order

The Cambrian period lasted 53 Million years and marked a dramatic burst of evolutionary changes in life on Earth known as the Cambrian Explosion

The Carboniferous period lasted about 363 to 290 million years ago the first reptiles cameabout and seed bearing plants there were extensive coral reefs and coal forming swamp forests the Carboniferous period has been divied into two parts the Mississippian and Pennsylvanian

The Devionan period or the age of fish Dawned 416 million years ago the planet was changing its appearance the Devionan period (age of fishes) had many many varieties of fish.

Ordovician was mostly oceans and most of the worlds land was collected into a southern super continent Gondwana. Earths climate was warm wet with sea levels rising as much as 1,970 feet above those today . But once Gondwana took up its polar position in late Ordovician massif England glaciers formed over Africa at the super continents center this started an ice age that lasted 20 million years during which shallow life rich seas shrank away

Permian is the last period it began 290 million years ago and lasted until 248 years ago the greatest mass extinction happened in this period temperatures were cooler becasuse the continent of Pangea was moving northword. The coral ref stared to build up. Horn coral Tabulate coral that had built up in the Devionan period was now gone

Silurian occurred from 443 to 416 million years ago it was the third period during this time landmasses were low and sea levels were rising. Much of the landmasses that would become western North America was under a shallow ocean for much of the Silurian period in the early Silurian period a class of jawless fish similar to the modern hangfish was most common

My sources http://science.nationalgeographic.com/science/prehistoric-world http://science.nationalgeographic.com/science/prehistoric-world/devonian/ http://science.nationalgeographic.com/science/prehistoric-world/ordovician/