This class includes fishes with bony endoskeleton. Fins also have bony rays.
Habitat: They are found in both marine and fresh water habitats.
Examples:
| Marine | Freshwater | Aquarium |
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| Exocoetus (Flying fish) | Labeo (Rohu) | Betta (Fighting fish) |
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| Hippocampus (Sea horse) | Clarias (Magur) | Pterophyllum (Angel fish) |
Body characteristics:
- Their body is streamlined.
- Mouth is mostly terminal.
- They have four pairs of gills which are covered by a bony operculum on each side.
- Skin is covered with cycloid/ctenoid scales. Some species do not have scales.
- They bear lateral line sense organs.
- Air bladder is present which regulates buoyancy.
- Heart is two chambered (one auricle and one ventricle).
Physiology: They are cold-blooded (poikilothermic) animals.
Notochord: Endoskeleton (notochord and cranium) is made of bone.
Reproduction: Sexes are separate. Fertilisation is usually external. Claspers are absent. They are mostly oviparous and development is direct.