A group of living things
Marsupials
Marsupialia
Born tiny, raised in a pouch
Its members' last common ancestor lived about 80 million years ago.
You and marsupials last shared an ancestor about 160 million years ago (on 18 December, if life's history were one year).
Marsupials start life amazingly tiny and usually keep growing in a pouch or fold of skin. A newborn can be as small as a honeybee or a jellybean, then crawls through fur to feed and drinks milk for months. Most mothers have a pouch or fold of skin on the belly for the baby.
They are mammals, and their closest cousins are the placental mammals shown beside them on the tree. Surprisingly, many live much like those cousins, as hunters, burrowers and anteater-like animals, but they feed their young in their own way, with a very short pregnancy and then a long time on milk. Most of the group — about seven in ten — live in Australia, Tasmania, New Guinea and nearby islands, while the rest live mostly in South and Central America, with one kind reaching North America.
Shapes vary a lot. Koalas are stocky with a round head and large fluffy ears, while red kangaroos have small front legs, huge back legs and a long thick tail. The smallest living kind is the long-tailed planigale, at only about 4 grams, while the red kangaroo can weigh up to about 90 kilograms and stretch well over 2 metres long including its tail. Different kinds live in deserts, grasslands, forests and mountains, and even in and beside streams.
Paused pregnancy
Many mother kangaroos can pause a fertilised egg and let it keep growing when the pouch is free or the pouch baby is lost.
Playing possum
When threatened, a Virginia opossum can flop over stiff with its tongue out and look dead, which is an involuntary reaction it cannot quickly stop.
Lost giants
Extinct relatives included plant-eaters as big as rhinos and a sabre-toothed hunter.