shows closer affinities with the black rhinoceros Diceros bicornis. It has been suggested that the modern white rhino has a longer skull than Ceratotherium praecox to facilitate consumption of shorter grasses which resulted from the long-term trend to drier conditions in Africa. However, if Ceratotherium praecox is in fact Diceros praecox, then the shorter skull could indicate a browsing species. Teeth of fossils assigned to Ceratotherium found at Makapansgat in South Africa were analysed for carbon isotopes and the researchers concluded that these animals consumed more than 30% browse in their diet, suggesting that these are not the fossils of the extant Ceratotherium simum which only eats grass. It is suggested that the real lineage of the white rhino should be; Ceratotherium neumayri → Ceratotherium mauritanicum → C. simum with the Langebaanweg rhinos being Ceratotherium sp. (as yet unnamed), with black rhinos being descended from C. neumayri via Diceros praecox. Recently, an alternative scenario has been proposed under which the earliest African Ceratotherium is considered to be Ceratotherium efficax (now synonymous with C. mauritanicum), known from the Late Pliocene of Ethiopia and the Early Pleistocene of Tanzania. This species is proposed to have been diversified into the Middle Pleistocene species C. mauritanicum in northern Africa, C. germanoafricanum in East Africa, and the extant C. simum. The first two of these are extinct, however, C. germanoafricanum is very similar to C. simum and has often been considered a fossil and ancestral subspecies to the latter. The study also doubts the ancestry of C. neumayri from the Miocene of southern Europe to the African species. The ancestor of both the black and the white rhinos was likely a mixed feeder, with the two lineages then specializing in browsing and grazing, respectively. The oldest definitive record of the White Rhinoceros is during the mid-Early Pleistocene at Olduvai Gorge in Tanzania, around 1.8 Ma. Southern white rhinoceros There are two subspecies of white rhino: the southern white rhinoceros (Ceratotherium simum simum) and the northern white rhinoceros. As of 31 December 2007, there were an estimated 17,460 southern white rhinos in the wild (IUCN 2008), making them by far the most abundant subspecies of rhino in the world; the number of southern white rhinos outnumbers all other rhino subspecies combined. South Africa is the stronghold for this subspecies (93.0%), conserving 16,255 individuals in the wild in 2007 (IUCN 2008). There are smaller reintroduced populations within