Important features of superclass Pisces: 

1. Habitat: These are aquatic animals and are present in fresh, marine and brackish waters. 

2. Body temperature: Pisces are poikilothermic animals i.e., cold blooded animals, in which body temperature changes according to the change in the surrounding temperature. 

3. Sensory organs:They have lateral line system which shows the presence of rheoreceptors for the detection of water current. 

4. Locomotion: Locomotion is by body muscles and fins. Caudal fin helps in steering wheel. 

5. Skeleton: Exoskeleton is made up of dermal scales. It is either bony or cartilaginous. 

6. Body shape: Body is streamlined and boat-shaped and helps to overcome resistance during swimming. 

7. Respiration: Respiration is by gills. 

8. Circulation: It shows single and closed circulation. Heart is two-chambered and ventral in position. Heart of fishes is described as venous heart (presence of deoxygenated blood). 

9. Nervous system: They have a well-developed brain with large olfactory lobes. 

10. Reproduction: Sexes are separate. Most of the fishes are oviparous, however some are viviparous.