We share the planet with about 12,000 kinds of mammals. They are incredibly varied, and survive in a variety of environments, usually through phylogenetic diversification. The Age of Mammals began about sixty million years ago, from tiny creatures going back perhaps 180 million years. Many more evolved and are extinct than now survive. [10]

"The average person probably does not even suspect the very existence of about ninety-five percent of extant mammals." [11]

The mammals have managed to fill "almost every niche". [12] ( )