Excerpt from "Prehistory of African Ruminant Livestock, Horses and Ponies" by Roger Blench in The Archaeology of Africa (1993) edited by Thurston Shaw, Paul Sinclair, Bassey Andah and Alex Okpoko (Link):
"The main present-day representation of the humpless longhorn in Africa is the n'dama, which flourishes between the Ivory Coast and the western seaboard (Starkey, 1984). Humpless longhorn cattle present something of a paradox. They are by far the most common type of cattle in iconographic representations in the Sahara, ancient north Africa and Ethiopia and are also clearly more ancient than shorthorns. Yet they are today confined to a very small region of western Africa."
"The humpless longhorns crossed the dessert, perhaps via a western route, as their geographical dispersal was never as broad as the shorthorns. Nonetheless, they seem to have adapted to the derived savanna and the northern forest regions and to have spread between the Senegambia and northern Cameroon. They presumably interbred with the muturu [See reference below], and the brown and white muturu types in semi-arid west Africa may be the descendants of these crosses. The humpless longhorns clearly illustrated in Ethiopian rock art have apparently vanished without trace, although they must have made some genetic contribution to present-day zebu races.
"Apart from the flourishing n'dama populations, there is more fragmentary evidence for a wider distribution of humpless longhorns in west Africa. Rock paintings in Birnin Kudu, northern Nigeria, clearly represent humpless longhorn cattle, and near Zing in northeastern Nigeria, are traces of a race that appears to be a humpless longhorn. They are kept by the Mumuye people, and are regarded as the 'traditional' type, although they have now almost disappeared on account of repeated crossing. Another residual population of these animals, locally known as pabli, has been recorded in northern Benin Republic (Troquereau 1961). Epstein (1971) cites existing populations among the Dowayo (Namji) and Pape in northern Cameroon as well as a record of a population in the Atlantika mountains that became extinct before 1939."
References (in order of citation):
Starkey, P. H. 1984. N'dama cattle - a productive trypanotolerant breed. World Animal Review 50, 2-15.
Adebambo, Olufunmilayo A. The muturo: A rare sacred breed of cattle in Nigeria (Link)
Troquereau, P. J. A. 1961. Les ressources animales de la République du Dahomey. Report to the Government of Dahomey.
Epstein, H. 1971. The Origin of Domestic Animals in Africa. 2 vols. New York: Africana Publishing Corporation.