Origins

According to Jack de Selby, mammals must have evolved from something else. 

I think that biology says that mammals evolved from reptiles that were not quite mammals (as we define them). Maybe from theracids, although my spell checker rejects them.

So mammals evolved from reptiles, and so did dinosaurs. But which came first, dinosaurs or mammals?

Some scientists believe that dinosaurs preceded mammals; others, that small mammals preceded dinosaurs. In any case, small mammals and giant dinosaurs once lived side by side. The Flintstones almost got it right.