Metatheria

Metatheria is the mammalian lineage that includes living marsupials and their extinct relatives. Its members are more closely related to marsupials than to placental mammals.

Mammalia: Mammalia is the class of vertebrates that includes monotremes, marsupials, and placental mammals. Metatheria is one of the major mammalian lineages.
Marsupial reproduction: Marsupial reproduction combines a short gestation with prolonged development of young after birth. This reproductive pattern is characteristic of many living metatherians.
Juramaia: Juramaia is an Early Cretaceous fossil mammal from China, once proposed as an early eutherian. Its classification illustrates how fossil evidence shapes estimates of metatherian and eutherian origins.
Sparassodonta: Sparassodonta is an extinct South American group of predatory metatherians. These predators occupied ecological roles often filled by placental carnivores elsewhere.
Eutheria: Eutheria is the mammalian lineage that includes placental mammals and their extinct stem relatives. Metatheria and Eutheria are the two principal branches of Theria.
Theria: Theria is the mammalian group comprising marsupials, placental mammals, and their extinct relatives. Metatherians belong to Theria, alongside the lineage leading to placental mammals.
Chorioallantoic placenta: The chorioallantoic placenta is a fetal membrane organ that mediates exchange between a fetus and its mother. Its extensive role in placental mammals contrasts with the typical brief gestation of marsupials.
Sinodelphys: Sinodelphys is a small Early Cretaceous fossil mammal from China, commonly interpreted as a metatherian. It is among the oldest fossils widely assigned to the metatherian lineage.
Thylacosmilus: Thylacosmilus is an extinct South American sparassodont with unusually long upper canine teeth. Its saber-like teeth make it a striking example of metatherian predatory specialization.
Monotremata: Monotremata is the mammalian lineage comprising egg-laying mammals such as platypuses and echidnas. Monotremes are mammals outside Theria and therefore outside Metatheria.

Linked from 8 pages