Struthio is a genus of birds in the order Struthioniformes, whose members are the ostriches. It is part of the infra-class Palaeognathae, a diverse group of flightless birds also known as ratites that includes the emus, rheas, and kiwis. There are two living species of ostrich: the common ostrich and the Somali ostrich. They are large flightless birds of Africa who lay the largest eggs of any living land animal. With the ability to run at 70 km/h (43.5 mph), they are the fastest birds on land. They are farmed worldwide, particularly for their feathers as they are used as decoration and feather dusters. Their skin is also used for leather products. Ostriches are notable for being the heaviest living birds.