Tortoises are reptile species of the family Testudinidae of the order Testudines (from the Latin name for tortoise). They are particularly distinguished from other turtles by being exclusively land-dwelling, while many (though not all) other turtle species are at least partly aquatic. Like other turtles, tortoises have a shell to protect from predation and other threats. The shell in tortoises is generally hard, and like other members of the suborder Cryptodira, they retract their necks and heads directly backwards into the shell to protect them.