The Class Actinistia comprises the coelacanths, an ancient group of lobe-finned fishes once thought extinct. They are characterized by fleshy, lobed pectoral and pelvic fins that resemble limbs, a hinged skull for wide gape, and a unique three-lobed tail. Coelacanths are deep-sea predators, feeding on fish and cephalopods, and are considered "living fossils" because they have changed little over hundreds of millions of years. They provide important insights into the evolution of vertebrates, particularly the transition from fish to tetrapods.