ORDER/CLASS Testudines (Anapsida): turtles. Body surrounded by a bony shell of dermic plaques. They lack teeth but possess a horny beak. Ribs and vertebrae fused to the shell. Anus is a longitudinal fissure. Distributed worldwide in tropical and temperate regions. 12 families and 245 species.

SUBORDER Cryptodira: hidden-necked turtles. They can retract their head to hide it inside the shell. Worldwide. 10 families.

SUPERFAMILY Chelonioidea

FAMILY Cheloniidae: sea turtles.
FAMILY Dermochelyidae: 1 especie, Dermochelys coriacea (leatherback turtle). The largest living turtle. No horny plaques, just a coriaceous hard cover.

SUPERFAMILY Testudinoidea

FAMILY Bataguridae: Old World freshwater turtles.
FAMILY Emydidae: New World freshwater turtles (terrapins).
FAMILY Testudinidae: tortoises. America, Europe, Africa and Asia.

SUPERFAMILY Trionychoidea

FAMILY Carettochelyidae: 1 species, Carettochelys insculpta (Papuan pitted-shelled turtle). New Guinea and North Australia. No horny plaques, just a soft coriaceous cover.
FAMILY Dermatemydidae: 1 species, Dermatemys mawii (Central American river turtle).
FAMILY Kinosternidae: American mud and musk turtles.
FAMILY Trionychidae: soft-shelled turtles. North America, Africa and Asia. No horny plaques, just a soft coriaceous cover.

FAMILY Chelydridae: snapping turtles. Central and North America.

SUBORDER Pleurodira: side-necked turtles. They can only fold the head aside to partially locate it under the fore edge of the shell. South America, Central and Southern Africa and Australasia. 2 families.

FAMILY Chelidae: snake-necked turtles. Long neck. South America, Australia and New Guinea.
FAMILY Pelomedusidae: crested side-necked turtles. South America, Africa and Madagascar.