(vertebrate zoology) An infraclass of therian mammals including a single order, the Marsupialia; distinguished by a small braincase, a total of 50 teeth, the inflected angular process of the mandible, and a pair of marsupial bones articulating with the pelvis.
Metatheria
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(′med·ə′thir·ē·ə)
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An infraclass of therian mammals including a single order, the Marsupialia. The Metatheria are distinguished from the Eutheria (the placental mammals) by numerous characters. The braincase is small, the angular process of the mandible is inflected, and a pair of marsupial bones articulates with the pelvis. Almost all living marsupials have a pouch on the belly of the female in which the young are carried after birth. The early marsupials were unable to compete with the more progressive later placental forms and died out except in South America and Australia, where they were isolated by water barriers. See also Eutheria; Mammalia.
| WordNet: Metatheria |
Note: click on a word meaning below to see its connections and related words.
The noun has one meaning:
Meaning #1:
pouched animals
Synonym: subclass Metatheria
| Wikipedia: Metatheria |
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 Lycopsis longirostris, an extinct metathere from the Sparassodonta, a sister taxon to the marsupials
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Metatheria is a grouping within the animal class Mammalia. First proposed by Thomas Henry Huxley in 1880, it is nearly synonymous with the earlier taxon Marsupialia (Illiger, 1811) though it is slightly wider since it also contains the nearest fossil relatives of marsupial mammals.
The earliest known representatives are from the uppermost Lower Cretaceous of North America.
The closest living relatives of the metatheres are the Eutheria (also erected by Huxley in 1880). Both are conventionally united as infraclasses within the subclass Theria (Parker and Haswell, 1897), which contains all living mammals except monotremes.
During development, metatherians produce a yolk sac placenta and give birth to "larval like" offspring. These offspring have under developed posterior limbs (the pes can be webbed), and following birth they migrate to the marsupium where they attach to a nipple. The mouth of newly born metatherians is fused laterally, but open medially; this forms an "O" shaped mouth in which the mothers nipple fits, then swells to secure the offspring into place for further development and growth.
The Greek words meta- and theria roughly means the "other beasts", in contrast with Eutheria ("true beasts").
See also
References
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This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (June 2009) |
- McKenna MC & Bell SK, (1997), Classification of Mammals Above the Species Level. Columbia University Press.
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