A group of living things
Hippos and whales
Whippomorpha
A river giant and an ocean giant are close cousins.
Its members' last common ancestor lived about 55 million years ago.
You and hippos and whales last shared an ancestor about 95 million years ago (on 23 December, if life's history were one year).
The hippo is the whale's closest living relative. That sounds strange, but their family link is close. Scientists once grouped hippos with pigs because their bodies and teeth look alike. Later work on genes showed whales are closer. Whales sit among hoofed mammals, alongside cows, sheep, giraffes and hippos.
A hippo has a huge barrel body on four short legs. Its eyes, ears and nose sit high on its head, so they stay above water while the rest hides below. A blue whale has a very long body with two short flippers and a wide flat tail. A large hippo can be up to about 5 metres long, about as long as a car. A blue whale can be up to about 30 metres long, about as long as three buses, and is the largest animal known to have lived.
Both can give birth in water and feed their young milk there. Both have very little hair. Hippos cannot truly swim. They walk along the riverbed and pop up to breathe. Hippos rest in shallow water by day and graze on grasses on the bank at night.
A giant that eats tiny food
A blue whale rushes at food with its mouth open. Its grooved throat swells to take in water and krill. It then pushes the water out through baleen and swallows what is trapped, about 4 tonnes a day when feeding.
Tongue like an elephant
A blue whale's tongue can weigh about as much as an elephant.
A tiny early relative
One early whale relative was a small deer-like animal only about 70 centimetres long. It had a thick ear bone for hearing underwater, just like whales.