Marsupialia

The group of the marsupial ( Marsupialia ), of the Greek marsipos “bag”, is a subclass of Mammifère S, at which the female has an abdominal pocket, except exception, also called Marsupium, in which it carries its small after its birth. The small one is born in a very incomplete level of development, near to the Fœtus, one names it marsupial larva . It remains in this pocket, attache with an udder of his mother, until it can nourish by itself.

The marsupials live all in Australia, Tasmanie or New Guinea, except for the Opossum and of the marsupial Musaraigne which live in America.

Some examples of marsupials: the Kangaroo, the Wallaby, the Koala, the Wombat, the Opossum. Many other species are known, like the marsupial Chat, and much disappeared.

The marsupials can be seen like the intermediate link between the Monotrème S Ovipare S and the Mammifère S Placentaire S.

Reproduction

The females of the marsupials have two Vagin S having a common opening but which are not amalgamated. The Placenta is hardly developed, whereas it is important in all the other mammals, except for the Monotrème S.

The genital conduit is formed starting from an opening which develops in conjunctive fabric between the two vaginae. The small ones are born in a very incomplete level of development, two to five weeks after their design.

Immediately after the birth, they migrate towards the abdominal pocket of the mother, at the species which have pockets, to anchor itself to an udder. This one dilates then to maintain the small one in place. They remain thus attached to an udder until they are enough large to seek their food by themselves.

Origins

The marsupials seem to have emerged during the Crétacé in the northern hemisphere, as lets it think the discovery of a fossil of Kokopellia old of 100 million years and found in Utah. The first proof of the presence of marsupials in Australia date of 55 My, i.e. after the Extinction of the Cretaceous.

Classification

The marsupials are generally arranged in 7 orders

order Dasyuromorphia Gill, 1872 -- carnivorous marsupials
order Didelphimorphia Gill, 1872 -- Opossum S or Sarigue S
order Diprotodontia Owen, 1866 -- Wombat S and Kangaroo S
order Microbiotheria Ameghino, 1889
order Notoryctemorphia Kirsch in Hunsaker, 1977
order Paucituberculata Ameghino, 1894
order Peramelemorphia Ameghino, 1889

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