What do the Basilosaurid fossilized bones show us? That they were an intermediate stage of development between land mammals and current whales? Or that they did not live in an aquatic environment but instead lived exclusively on land like desert like regions or they were type of fish? Which one is correct?

Answer 1

The Basilosaurid fossilized bones show us that they were an intermediate stage of development between land mammals and current whales. These animals were fully adapted to an aquatic lifestyle and lived in marine environments, not on land or in desert regions. They were not fish, as they were mammals that gave birth to live young and breathed air through their lungs.