The Paleozoic Era
The Paleozoic is the era of geologic time spanning about 541 to 248 million years ago. Paleozoic means ancient life (even though evidence of microbial life extends well back in time to some of the earliest sedimentary rocks still preserved and discovered on Earth). The Paleozoic Era follows the Precambrian Eon and precedes the Mesozoic Era. The term Paleozoic is used to describe the age of rocks that formed and accumulated in that time period. Highlights include:
• Dominant large animals: Invertebrates dominate early; fish and amphibians appear in the middle Paleozoic, and reptiles appear even later.
• Continents were mostly clustered together throughout the Paleozoic Era.
• Large, warm, clear, shallow seas covered large portions of continents.
• Similar animal and plant species existed on each continent.
• Continents were mostly low with little relief. Few large mountain ranges existed on and around most continental landmasses (compared with today).
• The combined Appalachians and Atlas Mountains formed 350 to 400 MYA (between what was North America and Africa before the opening of the Atlantic Ocean basin).