A group of living things
Turtles, crocodiles and birds
Archelosauria
Turtles turned out to be cousins of crocs and birds
Its members' last common ancestor lived about 255 million years ago.
You and turtles, crocodiles and birds last shared an ancestor about 320 million years ago (on 4 December, if life's history were one year).
At first glance a turtle looks a bit like a lumpy lizard. Scaly skin, clawed flippers or toes, eggs on land. But when scientists read more than a thousand shared stretches of DNA, turtles turned out to belong with a different group: crocodiles and birds. Lizards and snakes sit on a neighbouring branch of the tree.
Turtles are the only animals that build a shell outside the body from their own fused ribs, backbone and shoulder bones. The shell of a green sea turtle can grow to about one and a half metres long, about as long as a bathtub, and the turtle can weigh up to about 300 kilograms. Saltwater crocodiles are large water hunters with long tails and toothy snouts. Birds are living dinosaurs — even a city pigeon shares dinosaur roots with Tyrannosaurus rex.
Between them they live in warm seas, fresh waters and on land. Green turtles live in warm seas around reefs and seagrass, crocodiles hunt in rivers, swamps and where rivers meet the sea, and birds live almost everywhere, from deserts and forests to city parks and open ocean. Next time you watch a duck waddle and a turtle paddle, remember you are watching cousins.
Green means dinner, not shell
The green sea turtle is named for the greenish colour of its skin and body fat, not its brown or olive shell. The colour comes from its plant food.
Seaweed salads and jelly snacks
Adult green turtles feed mainly on seagrasses and algae, while young turtles also eat crabs, jellyfish and sponges.
A hundred eggs in the sand
Female green turtles crawl onto sandy beaches, dig a pit with their flippers and lay about 100 to 200 eggs. The babies hatch after about two months.