What mammals are out there, and how likely is it that they will stay around?
There are three subclasses of mammals.
The monotremes make up by far the smallest subclass of mammals, with just three species, found in Australia, Tasmania, and New Guinea. One of these is the duck-billed platypus, and the remaining two are the echidnas, or spiny anteaters.
There are about 250 species of marsupials, and they are found in a variety of habitats. About two-thirds of them live in Australia, Tasmania, or New Guinea, where they have evolved into a wide variety of forms, including plant-eaters such as kangaroos, koalas, and wombats, and also animals such as bandicoots and quolls, which have sharp teeth and feed largely on insects and other invertebrates. The remainder of the world's marsupials live in the Americas. They include about 70 different kinds of opossum, one of which—the Virginia opossum—is the only marsupial found in North America.
The third subclass of mammals, called placentals, includes about 4300 species, making it by far the largest of all three mammal groups. . . .
Biologists classify placental mammals into about 19 groups called orders (the exact number varies in different classification systems). The largest group, with about 1500 species, contains the rodents, such as rats, mice, squirrels, and porcupines. . . . Another major group of mammals, with about 1000 species, contains the bats. . . . Most large predatory land mammals belong to a group called the carnivores, which contains about 240 species. . . . Primates include animals such as lemurs, monkeys, apes, and humans, and most of the 230 species live in trees.
The world's large plant-eating mammals are divided into two major groups. One group, called the artiodactyls, contains animals such as hogs, deer, cattle, and antelope, which have hoofed feet with an even number of toes. The other, a much smaller group called the perissodactylas, includes horses, tapirs, and rhinoceroses, which have an odd number of toes.
Some mammals have adapted to life in the water. The seals, including sea lions and walruses, can sleep and feed in the open ocean but must return to land in order to reproduce. Manatees and dugongs are large, plant-eating mammals that spend their entire lives in the water. The whales, including the huge baleen whales and the dolphins, are well adapted as fast, open-ocean predators. Still, like all other mammals, aquatic mammals would drown if they could not reach the surface to breathe.
The orders of placental mammals are as follows (emphasis added):
Order Artiodactyla (even-toed hoofed animals)
Hoofed animals with an even number of toes include those that ruminate, or digest their food in four-chamber stomachs and chew cuds, and those that do not ruminate. Those that ruminate are the families Girrafidae (giraffes). Cervidae (deer, moose, reindeer, elk). Antilocapridae (pronghorn antelope), and Bovidae (cattle, bison, yaks, waterbucks, wildebeest, gazelles, springboks, sheep, musk oxen, goats). Nonruminators include the families Suidae (pigs), Tayassuidae (peccaries), Hippopotamidae (hippopotamuses), and Camelidae (camels, llamas).
Order Carnivora (meat-eaters)
There are two suborders of these toe-footed creatures. They include the Canidae (wolves, dogs, jackals, foxes), Ursidae (bears, giant pandas), Procyonidae (coatis, raccoons, lesser pandas), and Mustelidae (martens, weasels, skunks, otters), all part of one superfamily that is characterized by long snouts and unretractable claws; and Felidae (cats, lions, cheetahs, leopards) Hyaenidae (hyenas), and Viverridae (mongooses, civets), all of which have retractable claws.
Order Cetacea (whales and purpoises)
Two suborders of Order Cetacea are the toothed whales, which have regular conical teeth, and the baleen, or whalebone, whales, which have irregular whalebone surfaces instead of teeth. Toothed whales include the families Physeteridae (sperm whales), Monodontidae (narwhals, belugas), Phocoenidae (porpoises), and Delphinidae (dolphins, killer whales). Baleens are in the family Eschrichtiidae (gray whales), Balaenidae (right whales), or Balaenoptridae (fin-backed whales, hump-backed whales).
Order Chiroptera (bats)
There are two suborders of bats, the only mammals that can fly. Suborder Megachiroptera contains one family, the Pteropodidae (flying foxes, Old Worm fruit bats). Suborder Microchiroptera contains 17 families, including: Rhinopomatidae (mouse-tailed bats), Emballonuridae (sheath tailed bats), Craseonycteridae (hog-nosed or butterfly bats), Noctilionidae (bulldog or fisherman bats), Nycteridae (slit-faced bats), Megadermatidae (false vampire bats), and Rhinolophidae (horseshoe bats).
Order Dermoptera (colugos or flying lemurs)
These gliding tree mammals from Asia do not fly and are not lemurs, but they are known as flying lemurs, or Family Cynocephalidae .
Order Edentata (toothless mammals)
Three families of mammals get by without teeth: Dasypodidae (armadillos), Bradypodidae (sloths), and Myrmecophagidae (hairy anteaters).
Order Hyracoidae (hyraxes, dassies
Order Hyracoidae is one of three orders that has only one modern family remaining. Procavia capensis (the African rock hyrax) is one of nine living species in the Family Procaviidae .
Order Insectivora (insect-eaters)
The three members are the families Talpidae (moles), Soricidae (shrews), and Erinaceidae (hedgehogs).
Order Lagomorpha (pikas, hares, and rabbits)
Two families make up this order: Ochotonidae (pikas) and Leporidae (hares and rabbits of all sorts).
Order Marsupialia (pouched animals)
Included among these are the families Caenolestidae (rat opossums), Diddeelphidae (true opossums), Dasyuridae (native cats, native mice), Notoryctidae (marsupial moles), Myrmecobiidae (numbats), Peramelidae (bandicoots), Phalangeridae (koalas), Vombatidae (wombats), and Macropodidae (kangaroos and wallabies).
Order Monotremata (egg-laying mammals)
These more primitive mammals make up the families Tachyglossidae (echidnas, also called spiny anteaters) and Ornithorhynchidae (platypuses).
Order Perissodactyla (odd-toed hoofed animals)
The two suborders, Hippomorpha and Ceratomorpha, include creatures that have an odd number of toes. Families in this order are the Equidae (horses, donkeys, zebras), the Tapiridae (tapirs), and the Rhinocerotidae (rhinoceroses).
Family Manidae (pangolins) is the sole family in this order.
Order Pinnipedia (seals and walruses)
In the fin-footed order there are Otariidae (eared seals, sea lions), Odobenidae (walruses), and Phocidae (earless seals).
Order Primates (primates)
The order to which people belong is divided into two suborders: The Prosimii , who have longer snouts than their relatives, and the Anthropoidae . The first group includes the families Tupalidae (tree shrew), Lemuridae (lemurs), Daubentonlidae (aye-ayes), Lorisidae (lorises, pottos), and Tarsiidae (tarsiers). The anthropoids include the families Callitrichidae (marmosets), Cebidae (New World monkeys), Cercopithecidae (baboons, Old World monkeys), Hylobatidae (gibbons), Pongidae (gorillas, chimpanzees, orangutans), and Hominidae (human beings).
Order Proboscidea (elephants)
Large enough to have an order all to itself is Family Elephantidae .
Order Rodentia (gnawing mammals)
The most prolific mammals, Order Rodentia includes three suborders. It takes in the families Aplodontidae (mountain beavers), Sciuridae (chipmunks, squirrels, marmots), Cricetidae (field mice, lemmings, muskrats, hamsters, gerbils), Muridae (Old World mice, rats), Heteromyidae (New World mice), Geomyidae (gophers), and Dipodidae (jerboas).
Order Sirenia (dugongs and manatees)
The families Trichechidae (manatees) and Dugongidae (dugongs and other sea cows) make up the Order Sirenia .
Order Tubulidentata (aardvarks)
Another mammal in an order by itself is Family Orycteropodidae.