At least 28 vertebrate species, of which 22 are mammals, are recorded from the early middle Miocene (c. 16 m.y. old) fossil occurrence at Arrisdrift on the Orange River in South West Africa. The material postdates Miocene vertebrates previously recorded from the Namib desert. The mammals include at least 3 new species (a hyracoid, a palaeomerycid and an ochotonid), while there are at least 8 genera represented which have not hitherto been known in southern Africa. Austrolagomys simpsoni Hopwood, 1929, is referred to Kenyalagomys Whitworth, 1954, and Prohyrax is placed in the Pliohyracinae, a group which apparently had its origins in southern Africa.