Answer:
The Paleozoic Era, which lasted around 542 million years and ended 251 million years ago, was a period of significant change on Earth. The era started with the disintegration of one supercontinent and the emergence of another. Plants spread over the world. And the earliest vertebrate animals began to inhabit the land.
The Paleozoic Era
The Paleozoic Era began with the Cambrian Period, which lasted 53 million years and is best remembered for ushering in an explosion of life on Earth. The evolution of arthropods (ancestors of today's insects and crustaceans) and chordates was part of the "Cambrian boom" (animals with rudimentary spinal cords).
Life flourished in the waters during the Paleozoic Era. Following the Cambrian Period was the 45-million-year Ordovician Period, which is distinguished by an abundance of marine creatures in the fossil record.The trilobite, an armored arthropod that scurried over the seafloor for nearly 270 million years until becoming extinct, was perhaps the most famous of these invertebrates.
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