during which period did the first vertebrates appear
The Paleozoic Era, which ran from about 542 million years ago to 251 million years ago, was a time of great change on Earth. The era began with the breakup of one supercontinent and the formation of another. Plants became widespread. And the first vertebrate animals colonized land. Life in the Paleozoic. The Paleozoic began with the Cambrian Period, 53 million years best known for ushering in an explosion of life on Earth.