A new species of Trox, T. mozalae, from coastal sand forest in Mozambique, is described. T. natalensis quadricostatus Scholtz is elevated to species-level and T. natalensis schaborti Scholtz and T. elizabethae van der Merwe & Scholtz are synonymised with it. A key to the subgenus Phoberus MacLeay, to which most of the flightless species in Africa belong, is provided. All species incorporated into the key are illustrated by photographs of habitus and aedeagi. A map is provided of the distribution of each of them.