Bony fishes (Osteichthyes) have skeletons made of bone, swim bladders for buoyancy, and gill covers. This diverse group includes freshwater and marine species worldwide.
Cartilaginous fishes have skeletons made of cartilage instead of bone. This group includes sharks, rays, and skates, known for their sharp teeth and hydrodynamic bodies.
The oldest and most primitive fish species, lacking jaws, scales, and paired fins. These fishes have a bony skeleton, swim bladders for buoyancy, and bodies covered in scales.