At one time, Chondrichthyes were thought to have split off from other vertebrates before the evolution of bone. Now we have concluded that the Chondrichthyes split off after the evolution of bone had started. This change demonstrates .

Structural features are lost during evolution

Explanation:

In evolutionary biology it is well established the fact that the diversification processes may give rise to new structural characteristics as well as the loss of ancestral body structures, it depends on the evolutionary needs of each species

thinking it would be d not too sure but i think it's right