In every modern dipnoan, Crossopterygian, and Ganoid the air-bladder has an effective pneumatic duct.
Interest notes on dipnoan fin characters have been given by Traquair.
The name dipnoan may, however, be retained as a vernacular equivalent of Dipneusti.
In the archaic tail, enameled scales, and cartilaginous skeleton the Crossopterygian shows its affinity with its dipnoan ancestry.
It is not unlikely that the Crossopterygian gave rise to Amphibian and dipnoan alike.
The dipnoan and ganoid traits one by one are more or less completely lost.
Structurally the amphibian heart closely resembles the dipnoan, though the increased size of the left auricle is an advance.