The word Metatheria is formed from the Greek word meta meaning medium and ther meaning mammal. Mammals that have a pouch called a marsupium are called marsupials or metatheria. They live in Australia, Tasmania, New Guinea, Central and South America.
(i) They are simple immortal mammals.
(ii) They give birth to very immature neonates.
(iii) Female animals have pouch called marsupium. In this pouch the new-born attain fullness. Hence they are called marsupials.
(iv) Mammary glands including nipples are exposed in marsupium.
(v) They have two uteri and two vaginas.
Examples: Red kangaroo (Osphranter rufus/Macropus rufus), Virginia opossum (Didelphis virginiana), Koala (Phascolarctos cinereus).