Millions of years passed; great changes took place.
Parts of the land slowly sank beneath the seas, and out of the seas rose dry land.
Most of the larger reptiles died, but the mammals multiplied.
They grew to be as large as the fox or the sheep.
At first they were all very much alike and they lived in about the same way.
But as they became more and more unlike they had very different ways.
Some became like cats, and some like dogs.
An ancestor of our mammals
Some became like rhinoceroses and some like hogs.