marine mammals

Scientists classify all types of animals and plants by their genetic relationships to each other. This process is called taxonomy. As we have already seen, to be classified as a mammal you need to posses all 5 characteristics listed above. All mammals are members of the "class" Mammalia. Within this class are smaller subgroups called "orders". Three of these orders are made up entirely of marine mammals. They are the orders of Cetacea, Pinnipedia, and Sirenia. A fourth order Carnivora contains both marine and land animals.