Class 3. Dipnoi:
- These are found in freshwater.
- These are lungfishes, air bladder serving for aerial respiration.
- Operculum is present and there is only one external branchial aperture.
- Paired fins are lobate with jointed median axis.
- Notochord is persistent.
- Internal nostrils are present.
- A cloaca is present.
- Caudal fin is diphycercal, confluent with dorsal and anal fins.
