Characteristics of the Paleozoic Click on image for full size (115K JPG) L.Gardiner/Windows to the Universe (fossil images courtesy of AGI Imagebank)

Time:

• 545 to 248 million years ago
• (See the geologic timescale!)

Geography:

• Earth’s tectonic plates were on the move during the Paleozoic! By the end of this time they had moved so much that all of the continents were pushed together making one large continent called Pangaea.

Climate:

• 430 million years ago glaciers formed and ice covered the northern part of Africa. This area is a desert today, but back then it was located at the South Pole!
• Climate models have been used to understand the past weather patterns and climates of Pangaea. The models suggest that rainstorms called monsoons affected the East coast and that interior of continent was very dry.

Evolutionary Events:

• A large number of animals evolved between 530 and 520 million years ago including trilobites and brachiopods (pictured at left).
• During the early and middle parts of the Paleozoic, most animals lived in oceans. Animals without backbones (such as corals, brachiopods, mollusks, and trilobites) were very common.
• Animals with backbones (including fish, amphibians, and reptiles) began to flourish in the later Paleozoic. Animals and plants populated the land.
• About 250 million years ago, almost all of the species in the oceans became extinct. They didn’t die all at once. It took over 8 million years for the mass extinction to wipe them out.
• About 440 million years ago the Late Ordovician Mass Extinction was the second largest mass extinction of all time. Over 10 million years, many small marine species became extinct including those that built reefs.