There are 240 different kinds of tortoises, terrapins, and turtles to be found in the world today. The scientific name for the whole group is the Chelonia. The biggest is the leatherback turtle, which may reach 13 feet (1.8 m) in length and weigh an astonishing 1,500 lb (680 kg). The smallest is the speckled tortoise, which is only about 4 in (10 cm) long when fully grown.