Metatheria Temporal range: Lower Cretaceous – Holocene, 125 mya to present | |
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Lycopsis longirostris, an extinct Sparassodont, relatives of the marsupials | |
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Infraclass: | Metatheria |
Orders and infraclasses | |
Metatheria is a group in the class Mammalia which contains the marsupials and the sparassodonts.
First proposed by Thomas Henry Huxley in 1880, it is nearly synonymous with the earlier taxon Marsupialia, but it also contains the nearest fossil relatives of marsupial mammals.
The earliest known representative, Sinodelphys, is from the Lower Cretaceous of China.
The closest relatives of the metatheres are the Eutheria (also erected by Huxley in 1880). Both are conventionally united as infraclasses within the subclass Theria, which contains all living mammals except monotremes.
During development, metatherians produce a yolk sac placenta and give birth to 'larval-like' offspring.