A group of living things
Live-bearing mammals
Theria
Mammals that give birth to live young.
Its members' last common ancestor lived about 160 million years ago.
You are part of this group. See how.
You belong to this group of mammals that give birth to live young instead of laying eggs. Live-bearing mammals include two big branches: the pouch-raisers, such as kangaroos and koalas, and the placentals, such as bats, elephants, whales, dogs and humans. Their closest living relatives outside the group are surprising: the egg-laying platypus and echidnas.
A big difference is how long babies grow inside mum. Marsupials give birth very early to tiny, helpless young that crawl to a nipple and stay attached while they finish growing on milk. Placentals feed their young longer inside mum through her blood, so pregnancies can be much longer. Many marsupial mums have a pouch or fold of skin to shelter the young as they grow.
They live all over the world, on land, in water and in the air. They also vary hugely in size. The blue whale, the largest known animal ever, can grow longer than two buses and weighs up to about 200 tonnes.
Mostly Australian
There are over 330 kinds of marsupial. About two in three live in Australia, and most of the rest live in South America.
Double inventions
Burrowers, grazers, gliders and ant-eaters evolved separately among marsupials and among placentals.
Lone American
The Virginia opossum is the only marsupial that lives in the wild in the United States.