The extinct armored fish known as placoderms (plated skin) were considered the earliest branch of the jawed fishes. They achieved their greatest diversity during the Devonian "Age of Fishes" period (380 million years ago). Unlike jawed vertebrates, placoderms did not evolve from toothed ancestors and possessed razor-like, self-sharpening bony plates that functioned as teeth. Brachiopods (lampshells) and crinoids (echinoderms) dominated the ocean floor during this Mid-Devonian period.