Metatheria
| Metatheria Temporal range: Early Cretaceous – Holocene, 125–0 Ma |
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| Lycopsis longirostris, an extinct sparassodont, a relative of the marsupials | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Subclass: | Theria |
| Clade: |
Metatheria Thomas Henry Huxley, 1880 |
| Subgroups | |
Metatheria is a mammalian clade that includes all mammals more closely related to marsupials than to placentals (such as sparassodontans). First proposed by Thomas Henry Huxley in 1880, it is a slightly more inclusive group than the marsupials; it contains all of the living mammals with abdominal pouches (most female marsupials) as well as their more primitive ancestors and relatives. Metatherians are one of three main classes of extant mammals: monotremes (egg laying mammals like the platypus and the echidna), metatheria (or marsupials, which includes the three American orders (Didelphimorphia, Paucituberculata and Microbiotheria) and the four Australasian orders (Notoryctemorphia, Dasyuromorphia, Peramelemorphia and Diprotodontia)), and the eutherians (or placental mammals) consisting of twenty-one orders, divided into four superorders. Metatherians belong to a subgroup of the northern tribosphenic mammal clade or Boreosphenida. They differ from all other mammals in certain morphologies like their dental formula, which includes about five upper and four lower incisors, a canine, three premolars, and four molars. Other morphologies include skeletal and anterior dentition, such as wrist and ankle apomorphies; all metatherians share derived pedal characters and calcaneal features.
Below is a metatherian cladogram from Wilson et al. (2016):
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