What are the features of the organization of ancient beetle fish that make it possible to consider them the ancestors of terrestrial vertebrates?

this is the function of the lung by the swimming bladder; special structure of fins.
Pisterae are the ancestors of amphibians, because they had double breathing and limbs, with which they could move on land.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.