The Silurian is a geologic period and system that extends from the end of the Ordovician Period (440 million years ago), to the beginning of the Devonian Period. A significant evolutionary milestone during the Silurian was the appearance of jawed and bony fish. The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, to the beginning of the Carboniferous Period. Devonian to often be dubbed the "Age of Fish". The first ray-finned and lobe-finned bony fish appeared, while the placoderms began dominating almost every known aquatic environment.