The Paleozoic is the time period from 542 million years ago and 251 million years ago. During this period there was an explosion of life in the seas and on land. Life began in the seas and then spread to the land. Primitive plants covered the continents like great forests and many of these plants formed the coal beds of Europe and eastern North America.
Shown below are the Paleozoic displays in the Raymond M. Alf Museum of Paleontology on the campus of the The Webb Schools, a private residential high school, in Claremont, California.
According to a display at the Raymond M. Alf Museum of Paleontology:
“Insects, fish, reptiles, amphibians, trees, ferns, and much more emerged during the Paleozoic. Animals took their first steps onto dry ground. Tropical coral reefs covered much of what is now the continental United States.”
The Paleozoic is divided into six geologic periods: Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian.
Shown below are the Paleozoic displays in the Raymond M. Alf Museum of Paleontology on the campus of the The Webb Schools, a private residential high school, in Claremont, California.
According to the Museum display:
“The earliest forests would have been an otherworldly sight. Ferns and primitive trees—some towering over 100 feet tall—carpeted the landscape. Giant millipede-like animals up to 8 feet in length munched their way through the ground cover, which giant cockroaches scurried through dead vegetation on the forest floor and dragonflies buzzed through the trees.”
Mass Extinction
At the close of the Permian Period, 251 million years, there was a mass extinction. According to the Museum display:
“The Permian-Triassic extinction resulted in the extinction of 95 percent of all marine species and 70 percent of all terrestrial vertebrates. Trilobites and eurypterids which had flourished for over 200 million years went completely extinct, and many other groups were decimated. The ancestors of mammals, dinosaurs, and lizards barely survived.”
There have been a number of hypotheses regarding the cause of the extinction, including volcanism, glaciation, asteroid impact, and changes in atmospheric composition or ocean circulation patterns.