It is believed that the coelacanths and lungfish represent a crucial link between other fishes and tetrapods. What is the major feature in these fish in support of this hypothesis?

Their fins have skeletal and muscular structures similar to amphibian limbs.

Explanation:

Coelacanth is a special type of fish called lobfin. It is significant in evolution because it is a missing link between fishes and the amphibians. They evolved into the first amphibians that lived on both land and water. These were the ancestors of modern day frogs and salamanders.

Coelacanths are important for understanding the transition from water to land. Coelacanths were thought to be the ancestors of tetrapods a four-legged, land-living animals, but recent discovery of the coelacanth genome suggests that lungfish are actually more closely related to tetrapods.