Why were mammals able to become the dominant species at the beginning of the Cenozoic?

Question

Answer

The amphibians that first walked on land died out because it was too cold for them, after which mammals with fur took over.

Answer

The mammals were finally able to grow legs and come out of the ocean to populate the land.

Answer

Mammals evolved from primates after the dinosaurs went extinct and became the top predators.

Answer

The dinosaurs died off and the small rodent-like mammals of the Mesozoic evolved to fill the niche.

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