Teleost Diversity
Teleosts (advanced bony fishes) comprise over 30,000 species—more than all other vertebrate groups combined. They dominate every aquatic habitat from coral reefs to the deep abyss, from tropical rivers to polar seas. Key innovations that drove their success include the swim bladder (a gas-filled organ that provides neutral buoyancy without continuous swimming), highly mobile jaw mechanisms (protrusible mouths that can extend forward to capture prey), thin, flexible scales (reducing weight while maintaining protection), and a homocercal (symmetrical) tail that provides efficient propulsion. The enormous diversity of teleost body forms—from the streamlined tuna to the flattened flounder to the elongated moray eel—reflects adaptation to countless ecological niches over 200 million years of evolution.