A new species of Cacosternum Boulenger, 1887 (Anura: Ranidae) from the Karoo region of South Africa

A new ranid frog of the genus Cacosternum Boulenger, 1887 is described from the semiarid Karoo region of South Africa. This species is the putative sister species of Cacosternum namaquense Werner, 1910, but differs in that the two characteristic longitudinal dorsal glands of the latter species are absent and the musculus cutaneous pectoris is present. The two species differ further in their advertisement calls and substratum preferences. A discussion of the ecology and breeding biology of the two species is presented and their distributions mapped. Observational data suggest that growth to metamorphosis is rapid in these arid-adapted frogs, which are cued to breed primarily by rainfall events, not temperature or seasonality.