Metatheria es uno de los dos clados de mamíferos terios (el otro es Eutheria), y definido como más cercanamente relacionados con los marsupiales que con los placentarios. Propuesto inicialmente por Thomas Henry Huxley en 1880, es un grupo levemente más inclusivo que los marsupiales; este contiene a todos los mamíferos vivos con bolsas abdominales (mayormente marsupiales hembras) así como a sus más primitivos ancestros y parientes.

Leer el artículo completo en Wikipedia · CC-BY-SA

Metatheria is one of two mammalian clades, the other being Eutheria, with extant members that diverged in the Early Cretaceous or perhaps the Late Jurassic, and which includes all mammals more closely related to marsupials than to placentals. 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.

Leer el artículo completo en Wikipedia · CC-BY-SA