metatheria
/ˌmɛtəˈθɪriə/
noun
- A major group of mammals that includes marsupials (such as kangaroos, koalas, and opossums), characterized by giving birth to relatively undeveloped young that typically continue to develop in a pouch.
- The fossil record shows that Metatheria once lived in many parts of the world.
- Metatheria includes all marsupials, which are mostly found in Australia and the Americas.
- Unlike placental mammals, Metatheria have a different reproductive system.