Placodermi (extinct class)

Extinct class of vertebrate jawed fish-like animals known mainly from fossils of the Silurian and Devonian periods, having the head and pectoral region encased in broad, flat bony plates. Characterized by jaws supported by both cranium and hyoid arch, a partly ossified cranium, a head and trunk with armor that is jointed at the neck, often pelvic fins, pectoral fins or finlike structures, and gill arches.