Marsupials Click here for info on this order
which has been replaced by seven new orders. Includes what this order is, its families, and the layout of the new system.
Class Mammalia is a relatively small group of animals that are very well
known. There are approx. 4500 species of mammals, with very few left to be
discovered. Some discoveries are still possible, as is the case of the
cloudrunner, a squirrel-sized mammal discovered in the late 1990's.
All mammals have similar characteristics. First off, they all, just like other
vertebrates, have a backbone and spinal column. They also have a
notochord at some stage of development. All mammals are warm-blooded,
meaning they can control their body temperature. They can keep it at a
steady 36-38°C. Mammals lack feathers but rather are covered with fur or
hairy skin. They all have specialized teeth, with the exception of the
Edentates (armadillos), who lack teeth entirely. Mammal bones are solid
and filled with either marrow (as in humans) or spongy bone (as in
elephants). No mammals are completely cartilaginous. Mammals lack
wings, with the exception of Chiroptera (bats), which numbers to 900
species. All female mammals have mammary glands which produce milk for
the young. Mammary glands are the best way of defining mammals and is
where the term Mammalia came from.
Mammals are divided into 3 sub-classes based on their mode of
reproduction:
Subclass Prototheria
Prototheria is composed of egg-laying mammals. There are only 6 species of
these and they belong to one order:
Subclass Metatheria
Metatheria numbers to 250 species and is composed of seven orders (previously 1 - Marsupialia). Their young
are born tiny and immature and must climb into the mother's pouch, where
they grab hold of a teat and do not leave until they are mature.
Subclass Eutheria
The sub-class Eutheria is composed of all the placental mammals, whose young
form as embryos in the mother's stomach. Humans are an example of the
sub-class Eutheria. Below is a list of all 19 orders in this sub-class:
Monotremata (platypus and echidna)
Didelphimorphia (New World opossums)
Paucituberculata (South American rat opossums)
Microbiotheria (colocolo)
Dasyuromorphia (dasyurids, thylacines)
Peramelemorphia (bandicoots)
Notoryctemorphia (marsupial moles)
Diprotodontia (kangaroos, koalas, wombats, possums) Insectivora (moles, shrews)
Dermoptera (flying lemurs)
Chiroptera (bats)
Cetacea (whales)
Carnivora (cats, bears, dogs, otters, seals, sea lions)
Tubulidentata (aardvarks)
Proboscidea (elephants)
Hyracoidea (hyraxes)
Primates (monkeys, lemurs, bushbabies, aye-ayes)
Xenarthra or Edentata (armadillos, anteaters, sloths)
Pholidota (pangolins)
Lagomorpha (rabbits, hares, pikas)
Rodentia (mice, rats, squirrels, porcupines, beavers, voles, hamsters)
Sirenia (manatees, dugongs)
Perissodactyla (horses, donkeys, zebras, rhinoceroses,tapirs)
Artiodactyla (pronghorns, deer, camels, gnus, goats, giraffes,
hippopotami, pigs, peccaries, chevrotains, musk-deer, cows)
Scandentia (tree shrews)
Macroscelidea (Elephant Shrews)
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