Of, relating to, or being the era of geologic time from about 542 to 251 million years ago. The Paleozoic Era includes the Cambrian, Ordovician, Silurian, Devonian, Mississippian, Pennsylvanian, and Permian Periods and is characterized by the appearance of marine invertebrates, primitive fishes, land plants, and primitive reptiles. The end of this era is marked by the largest recorded mass extinction in the earth's history, in which 90 percent of marine life forms were wiped out. See Table at geologic time.

The Paleozoic Era.