... most important features of this period is the appearance of nearly all of the invertebrate animal phyla in abundance. A few fishlike invertebrates and vertebrates appeared in the Cambrian and Ordovician. Scorpions, land invertebrates, amphibians, land reptiles and marine reptiles also appeared. Reptiles increased in number and plant life reached its climax. Great crystal commotion marked the end of the Paleozoic era ... ...

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• Grade Level: Undergraduate