marsupial

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marsupial

(märso͞o`pēəl), member of the order Marsupialia, or pouched mammals. With the exception of the New World opossumsopossum
, name for several marsupials, or pouched mammals, of the family Didelphidae, native to Central and South America, with one species extending N to the United States.
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 and an obscure S American family (Caenolestidae), marsupials are now found only in Australia, Tasmania, New Guinea, and a few adjacent islands. They are generally distinguished from placental mammals by the absence of a placenta connecting the embryo with its mother, although in a few forms the female has a rudimentary placenta that functions for a short time.

The embryo is nourished during its brief gestation by a fluid secreted by the mother's uterus. The young are born in a very undeveloped state; at birth the great gray kangarookangaroo,
name for a variety of hopping marsupials, or pouched mammals, of the family Macropodidae, found in Australia, Tasmania, and New Guinea. The term is applied especially to the large kangaroos of the genus Macropus.
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 is about 1 in. (2.5 cm) long and the opossum about 1 1-2 in. (3.8 cm) long. Immediately after birth the young crawl to the mother's nipples and remain attached to them while continuing their development. As they are still too helpless to suckle, milk is squirted into them by the periodic contraction of muscles over the mother's mammary glands.

In nearly all marsupials the female's nipples are covered by a pouch, or marsupium, formed by a fold of abdominal skin. Even after the suckling stage the young return at times to the pouch for shelter and transportation. In many species the young are carried on the mother's back after the suckling stage. In addition to having a less efficient reproductive system than the placental mammals, marsupials are of generally lower intelligence.

Marsupials were once widespread over the earth, but were displaced in most regions as the more successful placental mammals evolved. The Australian region, which has been isolated from contact with other regions since the Cretaceous period, had almost no native placental mammals, and the marsupials were able to continue their evolution there without competition. They underwent an adaptive radiationadaptive radiation,
in biology, the evolution of an ancestral species, which was adapted to a particular way of life, into many diverse species, each adapted to a different habitat.
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 in Australia comparable to that of placental mammals in the rest of the world, evolving many forms that superficially resemble various placental mammals and fill the same ecological niches. Thus, there are animals known as Tasmanian wolves (see thylacinethylacine
or Tasmanian wolf,
carnivorous marsupial, or pouched mammal, of New Guinea, Australia, and Tasmania, presumed extinct since 1936. The thylacine is often cited as an example of convergent evolution: It was superficially quite similar to a wolf or dog, although
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), marsupial moles, marsupial mice, and native cats (see dasyuredasyure
, name for several small, predatory marsupials, or pouched mammals, of the family Dasyuridea, found in Australia, Tasmania, and New Guinea. Typical dasyures, known in Australia as native cats, are furry animals with large eyes, pointed snouts, and long tails.
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), which live very much like the correspondingly named placental mammals and, in many cases, are strikingly similar in appearance. See also bandicootbandicoot,
small marsupial mammal native to Australia and nearby islands. There are 19 species in eight genera. Bandicoots have long, pointed, shrewlike faces; gray or brown fur; and long, bushy, ratlike tails. They range in size from that of a rat to that of a rabbit.
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, numbatnumbat
, small marsupial, of SW Australia, also known as the marsupial anteater. The numbat, Myrmecobius fasciatus, resembles a squirrel in size and general appearance, but is adapted for eating insects, with a pointed snout and a long, cylindrical tongue covered with a
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, phalangerphalanger
, any of the numerous and varied marsupials, or pouched mammals, of the family Phalangeridae, found in Australia, New Guinea, and adjacent islands. Many are somewhat like squirrels in appearance.
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, Tasmanian devilTasmanian devil,
extremely voracious marsupial, or pouched mammal, of the dasyure family, now found only on the island of Tasmania. The Tasmanian devil, Sarcophilus harrisi, formerly found also in Australia, is about 2 ft (60 cm) long, excluding the 12-in. (30-cm) tail.
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, wombatwombat,
shy marsupial of Australia and Tasmania, related to the koala. The wombat is a thick-set animal with a large head, short legs (giving it a shuffling gait), and a very short tail. It is about 3 ft (91.5 cm) long.
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.

Bibliography

See H. Tyndale-Biscoe, Life of Marsupials (1973); A. K. Lee and A. Cockburn, Evolutionary Ecology of Marsupials (1985).

marsupial

[mär′sü·pē·əl]
(vertebrate zoology)
A member of the Marsupialia.
Having a marsupium.
Of, pertaining to, or constituting a marsupium.

marsupial

any mammal of the order Marsupialia, in which the young are born in an immature state and continue development in the marsupium. The order occurs mainly in Australia and South and Central America and includes the opossums, bandicoots, koala, wombats, and kangaroos