This order is represented by a single family restricted to Africa, Struthionidae (ostriches), with two species in a single genus, Struthio:
Traditionally regarded as a single species, Struthio camelus (Ostrich), mitochondrial DNA data seem to justify the distinction of two species,
Struthio camelus (Common Ostrich) and Struthio molybdophanes (Somali Ostrich). Common and Somali ostriches are thought to have been sparated by the formation
of the East African Rift Valley some 4 mya.
Young Common Ostrich (Struthio camelus) in bristly camouflage plumage. In danger, young
ostriches stretch themselves motionless out on the ground, which makes them appear like a tuft of gras (mimesis).
Head of a Common Ostrich (Struthio camelus). In ostrich farms these birds are very curious. Reaching a top speed of about 70 km/h, or 45 mph, ostriches are the fastest running birds in the world.
del Hoyo, J., N.J. Collar, D.A. Christie, A. Elliott, and L.D.C. Fishpool (2014), Illustrated Checklist of the Birds of the World, volume I
(Non-passerines), published by Lynx Edicions in association with BirdLife. (link)
Freitag, S. and T.J. Robinson (1993), Phylogeographic patterns in mitochondrial DNA of the Ostrich (Struthio camelus), The Auk 110 (3),