Paleozoic Era

Cambrian Period: 541 - 485 million years ago

Famous Animals: Trilobites

About: The Cambrian period marked the point in time when the diversity of multi-cellular life exploded. Most famous of these invertebrates were the trilobites, which happen to be Wisconsin’s state fossil.

Ordovician Period: 485 - 443 million years ago

Climate: Tropical near the equator, cold near the poles

Famous Animals: Trilobites, nautiloids, early fish

About: Life continued to evolve during this period of time. Though rare, some of the first plants, probably similar to lichens and moss, made their way on land. Most of the land above the oceans was desert-like, having no plant-life.

Silurian Period: 443 - 419 million years ago

Climate: Very cold initially, but as time progressed, the planet warmed up significantly

Famous Animals: Eurypterids ("Sea Scorpions”)

About: Following a large extinction event, the species that survived became more complex. Brachiopods and gastropods diversified, and some of the first arthropods ventured on land. Trilobites, having had their time, began to decline as more advanced species took their places.

Devonian Period: 419 - 359 million years ago

Climate: Warm and dry

Famous Animals: Dunkleosteus, sharks

About: Sometimes known as the "Age of Fish,” the Devonian was a period of time when huge fish and small sharks owned the seas, and some of the first tetrapod animals ("Four feet”) evolved, the ancestor to early amphibians. The first forests developed on land.

Carboniferous Period: 359 - 299 million years ago

Climate: Warm for the first half, an ice age during the second

Famous Animals: Giant dragonflies

About: The Carboniferous has been nicknamed the "Coal Age” because this is where the majority of the world’s coal deposits first originated. High oxygen levels allowed insects to grow to massive proportions. The first pseudo-reptiles evolved, and quickly diverged into the groups that eventually became the mammals and reptiles.

Permian Period: 299 - 252 million years ago

Climate: Gradual warming, becoming arid. Great seasonal variety depending on location

Famous Animals: Dimetrodon, Edaphosaurus

About: The Permian had a wide variety of plant and animal life, with astounding herbivores and carnivores living in all different ecological niches. That is, until the Permian extinction event that ended the Paleozoic era. This event is believed to have been caused by massive volcanic activity in Siberia, and killed approximately 90% of all life on our planet, given an adequate advantage to small reptiles that eventually evolved into dinosaurs during the Mesozoic era...