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 ________.

Question

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The dorsal fins and tails of ichthyosaurs and fish are adaptations to a common environment (aquatic) and are examples of convergent evolution, as they evolved independently in different lineages. They are not homologous structures, as they did not evolve from a common ancestor that also had these structures.

Ichthyosaurs, Now Extinct, Were Aquatic Reptiles with Dorsal Fins and Tails