During the Palaeozoic Era (542 – 252 million years ago), plants and animals moved from the seas to inhabit dry land. At around 300 million years ago, during the Carboniferous Period, diverse communities of plants and animals covered the planet. Just as life was flourishing, a mass extinction wiped out 90% of life on Earth at the end of the Permian Period, 252 million years ago. Known as the Great Dying, this was Earth's most severe extinction event, and marks the boundary between the Palaeozoic and Mesozoic eras.
Often mistaken for a dinosaur, Dimetrodon was the most impressive mammal-like reptile of the Permian Period.