The Devonian

The Devonian, the Age of Fish, saw a massive diversification of fish species. In particular, the bony fish, which first appeared during the Silurian, diverged into two major groups - the ray-finned fish and the lobe-finned fish. Perhaps due in part to the increased competition in the Devonian ocean, a lineage of lobe-finned fish would give rise to the first terrestrial vertebrates, the tetrapods, during the latter half of the period. Also on land, plants got their first true roots. The Devonian would end in a mass extinction event that would wipe out nearly 75% of the extant species on the planet.