Blackwell Publishing



Radiation is a period in the fossil record in which it can be seen that the rate at which new species arise in a taxonomic group far exceeds the rate at which species go extinct. In other words, a taxonomic group greatly proliferates through the environment.

The increase in the number of mammal families 60 - 40 million years ago was a radiation which saw the emergence of new mammal species. This manatee opposite, for example, arose to fill an ecological niche in the sea.

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