Sea turtles (superfamily Chelonioidea), sometimes called marine turtles, are reptiles of the order Testudines. There are seven species of sea turtles. They are the leatherback sea turtle, green sea turtle, loggerhead sea turtle, Kemp's ridley sea turtle, hawksbill sea turtle, flatback sea turtle and olive ridley sea turtle. Four of the species have been identified as "endangered" or "critically endangered" with another two being classed as "vulnerable".