Ichthyosaurs, now extinct, were aquatic reptiles with dorsal fins and tails, similar to those of fish. Their most recent ancestors were terrestrial reptiles that had neither dorsal fins nor aquatic tails. The dorsal fins and tails of ichthyosaurs and fish are .

Adaptations to a common environment and examples of convergent evolution

Explanation:

Fish and ichthyosaurs are two different species that have independently evolved and developed dorsal fins and tails which were absent in their last common ancestors that they have evolved from. The dorsal fins and tails of ishthyosaurs and fish are similar in function and structure, as they have been developed or evolved as adaptations to swimming.

These dorsal fins and tails of ishthyosaurs and fish are referred to as analogous structures that have been evolved independently to adapt to swimming in the evolutionary process known as convergent evolution.

The dorsal fins and tails of ishthyosaurs and fish are adaptions to a common environment and examples of convergent evolution, as both do not have evolved these structures independently.

the statement is true

i think its the first one