Fish can be dated back to 510 million years ago. Various types of fish appeared in the succeeding 150 million years. Fish without jaws or hard bones.
Fish with hard bony shields. Fish with spiny fins. Fish with hard back-bones. Fish with bones supporting their fins. Fish greatly diversified in the Silurian and Devonian Periods. In the Devonian Period, sometimes referred to as the "Age of Fish", nearly every major group of fish, including those extinct today, flourished. The present day fish are their descendants, surviving through the history of extinction and evolution.

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