Marsupials represent the group of mammals existing since ancient times. Australia is called sometimes the continent of marsupials of animals as there them lives much.
Why Australia
To say that almost all animals of Australia are marsupials it would not be absolutely right. It would be more correct to tell that almost all marsupials of the world live on this continent. And to that there are reasons.
Several millions years ago when continents were not divided, marsupials animals inhabited all planet. However as the fauna became more and more various and the quantity of other species of mammals increased, they gradually forced out marsupials. The fact is that placentary animals were more adapted for changes in climate and the environment. Therefore marsupials, being more difficult organized beings, disappeared on the majority of continents over time. On the Australian continent they managed to survive as it was surrounded with water, and animals from other continents could not migrate here.
Species diversity
In the world total more than 200 species of marsupials. Among them is herbivorous, insectivorous and predatory. The sizes of representatives of different types can differ very strongly. So, the sumchaty mouse of Kimberley has body length from 10 cm, and the big gray kangaroo can reach and 3 m. Among the Australian marsupials the red kangaroo is most widely known to people. Besides, there are the wood kangaroo who is also living on trees, an opossum, phlegmatic a koala, the wombat living in underground tunnels, a dangerous tasmaniysky devil, insectivorous bandinut, a sumchaty mouse, a big-eared marsupial a badger (rabbit is bandinut), a marsupial a jerboa, a sumchaty marten (kvolla), etc.
Besides Australia, many marsupials of animals live also in South America now.
Characteristic differences of marsupials
Difference of these mammals from placentary that the cub develops not in a body of a female, and in her bag on a stomach. At marsupials, in particular, at a kangaroo, the cub is born a usual way then he crawls to a bag, gets into it and hangs on one of mother's nipples. It is surprising, considering that the newborn kengurenok is externally similar to an embryo, it the blind person and the deaf, about 2 cm in size. It grows in a bag several months before is able to leave it.
The majority of marsupials of animals lead a nocturnalism.
Only females have bags. Both for females, and existence of special pelvic bones is characteristic of males. Bags at animal species are developed in different degree. The majority of insectivorous has no full-fledged "pocket", and there is only a small fold.