Actinistia is a group of ancient fish known as coelacanths, which were thought to have been extinct for about 66 million years until one was discovered off the coast of South Africa in 1938. These fish are characterized by their unique lobed pectoral and pelvic fins, which resemble the limbs of land vertebrates. Coelacanths are deep-sea dwellers, typically found at depths of 150 to 700 meters. They have a distinctive, thick, and bony body covered in a layer of scales. Their evolutionary history provides valuable insights into the transition of life from water to land, linking them to early tetrapods.