Cladistia is an ancient lineage of ray-finned fishes that includes the order Polypteriformes, represented today by bichirs and the reedfish of tropical Africa. Members of Cladistia are distinguished by several unusual anatomical features, including heavy ganoid scales, a series of separate dorsal finlets rather than a single continuous dorsal fin, and fleshy pectoral-fin bases supported by a distinctive internal skeleton. They also possess paired lungs that allow them to breathe atmospheric air, an adaptation that enables survival in warm or oxygen-poor freshwater habitats where dissolved oxygen may become limited. Cladistia occupies an early-diverging position within Actinopterygii, making its living members especially important for understanding the evolutionary history and anatomical diversification of ray-finned fishes.
