Marine mammals

The first mammals emerged over a hundred million years ago, but it was the great extinction that occurred at the end of the Cretaceous Period that offered mammals the opportunity to thrive and become the dominant species of terrestrial animals. About 50 million years ago, mammals also began to colonise the nseas and oceans, and though these are still dominated by fishes, mammals were established at the top of the ecological pyramid, and a group of species, the whales, became the largest animal species in the planet's history, greater than the giant dinosaurs.

Evolución de las ballenas

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