A 250-million-year-old puzzle
Scientists tell us that about 250 million years ago there lived a big
reptile called Dimetrodon. It was about as long as a small automobile.
It ate smaller reptiles.
Dimetrodon had a big fin like a sail on its back. Scientists think the
fin helped a Dimetrodon warm up
or cool off. After a cool night, a stiff, cold Dimetrodon might lie with
its fin facing the sun, and the fin would quickly get warm. The warmth
would spread into the Dimetrodon’s body. But a Dimetrodon that was too
hot could lie with the thin edge of the fin facing the sun. Then, the
fin would cool off.
