Their young are born in an immature state after a relatively short developmental period in the mother's uterus. (This is called the gestation period.).
The newborn marsupial crawls into a pouch or onto a pouch-like area on the mother's abdomen. Here it attaches itself to one of her nipples and remains until it is well formed and has grown much larger.
There are some 250 kinds of living marsupials. These include the Australian and New Guinean insectivorous and carnivorous (insect and meat-eating) marsupials, the omnivorous (plant and meat-eating) bandicoots, and the herbivorous (plant eating) possums, koalas, wombats and kangaroos as well as the South American opossums.
Scientists have grouped them according to differences in their dentition. They are either polyprotodonts (with many teeth and always three pairs of incisors on the lower jaw) or diprotodonts (fewer teeth with only one pair of especially well-developed incisors on the lower jaw).
Characteristics of their pouch, fore and hind foot structure, nature of tail and whether they are tree-dwellers, burrowers or ground-dwellers, help to classify them further.
Mammals that can live on land and prey on other animals tend to look similar. The adaptations for chasing, catching and eating other animals are a compact body, four slender limbs, claws and a head with well-developed organs of sight, hearing and smell.
In other words, all the marsupial carnivores are superficially similar and resemble placental cats, shrews, dogs and other animals that share the carnivorous habit.