Yoozer_Naym

I've noticed lately how out of all the classes of the animal kingdom, that mammals appear to be the most diverse in anatomy and physiology. I find this particularly interesting since there are very few mammal species. Even more interesting to me is that mammals not only make up such a small group, but we have only been on this earth such a short time compared to most other animal groups such as insects, amphibians, reptiles, etc. But as many kinds of insects there are, they all seem to have more in common anatomically to one another than the few mammal species do. Take, for example a mouse, a lion, an elephant, a bat, a whale, a giraffe , and a human. Now look at how drastically different all those animals look from each other. Yet if you go back in time to before the dinosaurs went extinct just 65 mya, the common ancestor for humans and elephants (to my knowledge)looked like some rodent. Now you can go back hundreds of millions of years and find that a lot of groups of reptiles such as crocodilians and turtles which are still around today, were pretty much the same. Same goes for fish and arthropod groups(by groups I mean classes,orders,families, genera,etc). So what I would like to know is how have mammals, who are so young and so low in numbers have diversified so much so quickly? Is there something about mammals that are unique, or is there something I'm missing? By the way, if anything I said here is incorrect, please feel free to set me straight. Thanks.