A group of living things
Mammals
Mammalia
Fur and milk: from egg-laying platypuses to us.
Its members' last common ancestor lived about 180 million years ago.
You are part of this group. See how.
You are a mammal, and so is the egg-laying platypus. That is the surprise of this family. Hair or fur and milk link us to whales, bats, kangaroos and dogs. All mammals share three things found together nowhere else: hair or fur, milk for their young, and three tiny bones in each middle ear.
Even the egg-layers fit. Only five kinds survive today, including the platypus and the short-beaked echidna, and their milk simply oozes from pores on the mother's belly. In furry mammals, fur keeps them warm by trapping warm air near the skin. Many have whiskers that help them feel their way, especially at night.
Mammals live on every continent and in every ocean. Different kinds walk, hop, climb, dig, swim, dive or fly. Sizes stretch from the tiniest bats and shrews, about as big as a bumblebee, weighing about as much as a paperclip, to the blue whale, as long as a passenger jet and as heavy as about 30 elephants.
A bill that feels electricity
A platypus closes its eyes and ear openings with each dive and hunts by touch and electricity. Its leathery bill holds about 40,000 sensors that pick up tiny electric signals from prey.
Smaller than a cherry
A newborn red kangaroo is smaller than a cherry. It climbs straight into its mother's pouch and does not come out for about two months.
A tongue for termites
An echidna's long sticky tongue can sweep up to about two kilograms of ants and termites in a single meal.