Book 33, Question 23
Why did mammals get bigger and more varied after the dinosaurs?
For millions of years, most mammals were small.
About 66 million years ago, the big dinosaurs disappeared, and many places opened up for new animals. Mammals took advantage. Over time, some grew large, some learned to swim, and some took to the air. Today there are tiny shrews and huge elephants. Open spaces gave mammals room to change.