Chondrichthyes:
- They are marine animals with streamlined body
- Cartilaginous endoskeleton.
- Mouth is located ventrally.
- Gillslits are separate and without operculum (gill cover)
- The skin is covered by minute placoid scales.
- Due to the absence of air bladder, they have to swim constantly to avoid sinking.
- They are mostly viviparous
- Fertilization is internal
Ostelchthyes:
- It includes both marine and Fresh water Fishes
- Bony endoskeleton.
- Mouth is mostly terminal.
- The gills are covered by an operculum on each side.
- Skin is covered with cycloid/ctenoid scales.
- Air bladder is present which regulates buoyancy.
- They are mostly oviparous
- Fertilization is external
