Sea turtles
Sea turtle
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Sauropsida
Order:	Testudines
Suborder:	Cryptodira
Superfamily:	Chelonioidea Bauer, 1893
Genera
Family Cheloniidae (Oppel, 1811) Caretta Chelonia Eretmochelys Lepidochelys Natator Family Dermochelyidae Dermochelys Family Protostegidae (extinct) Family Toxochelyidae (extinct) Family Thalassemyidae (extinct)

Sea turtles (Chelonioidea) are turtles found in all the world's oceans except the Arctic Ocean, and some species travel between oceans. The term is US English. In British English they are simply called "turtles"; fresh-water chelonians are called "terrapins" and land chelonians are called tortoises.

The earliest known turtles are from the Middle Jurassic. So, turtles are one of the oldest surviving reptile groups: they are more ancient than snakes or crocodiless.

There are seven species of sea turtle: Kemp's ridley sea turtle, the olive ridley, the flatback, the green, the loggerhead, the hawksbill and the leatherback.