The Paleozoic Era, which ran from about 542 million years ago to 251 million years ago

http://www.livescience.com/37584-paleozoic-era.html

And the first vertebrate animals colonized land.

http://www.livescience.com/37584-paleozoic-era.html

By the end of the Paleozoic, cycads, glossopterids, primitive conifers, and ferns were spreading across the landscape

This is a cycads

http://www.ucmp.berkeley.edu/paleozoic/paleozoiclife.html

glossopterids

http://www.ucmp.berkeley.edu/paleozoic/paleozoiclife.html

primitive conifers

http://www.ucmp.berkeley.edu/paleozoic/paleozoiclife.html

Fern

http://www.ucmp.berkeley.edu/paleozoic/paleozoiclife.html

BThe Permian extinction, 244 million years ago, devastated the marine biota: tabulate and rugose corals, blastoid echinoderms, graptolites, and most crinoids died out, as did the last of the trilobites.

http://www.ucmp.berkeley.edu/paleozoic/paleozoiclife.html

The climate of the Paleozoic Era varied as the period began with large glaciers covering the surface of the Earth, which gave way to warmer temperatures, glacial melt and volcanic activity

https://www.reference.com/history/paleozoic-era-climate-ba2b59ab180e8205

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,

The Paleozoic Era ended with the largest mass extinction in Earth's history, the Permian–Triassic extinction event

https://sites.google.com/site/earthshistoryproject/Home/precambian-time

The effects of this catastrophe were so devastating that it took life on land 30 million years into the Mesozoic Era to recover.

https://sites.google.com/site/earthshistoryproject/Home/precambian-time