Mammalia class, Mammals, are a group of very diversified animals thanks to certain adaptations suffered over time, qualities that have served to conquer virtually all means: land, sea and air, keep in mind that part of In terrestrial species, there are mammals that have the ability to fly, such as bats, others are aquatic, for example, dolphins and whales.
Humans belong to the Mammalia class, Hominid family and genus Homo, we are the only species in that genus. There are other non-mammalian vertebrates, however, the latter present the dental bone of the lower jaw articulated with the skull, a key character to identify it as such, regardless of other aspects that will be detailed below.The origin of the mammals dates back to about 245 million years ago, at that time they were small insectivorous animals descended from terrestrial reptiles of the Triassic. In the Cretaceous, after the disappearance of the dinosaurs, its evolution begins occupying its corresponding ecological niches. As scientists consider the group as monophyletic (with a common ancestor).