Two new mastodonsaurid temnospondyls are described from the Early to Middle Triassic Cynognathus Assemblage Zone of the Upper Beaufort Group (Karoo Basin) of South Africa. Paracyclotosaurus morganorum, sp. nov. is based on a partial skull from the uppermost part of the Cynognathus Assemblage Zone (Subzone C; late Anisian) in the southern Karoo Basin, and is the first occurrence of the genus Paracyclotosaurus outside of India and Australia. Jammerbergia formops, gen. et sp. nov. is based on a partial skull, presumably from Subzone B (early Anisian) of the Cynognathus Assemblage Zone, and is distinctive in its unique suite of primitive and derived characters. Although the intrarelationships of mastodonsaurids remain largely unresolved, the two most recent analyses are similar in the identification of an ‘advanced’ mastodonsaurid clade whose members are characterized by laterally directed tabular horns. Jammerbergia probably belongs within this clade, albeit within a basal position. Jammerbergia and Paracyclotosaurus share the synapomorphy of large, antero-posteriorly expanded tabulars, and may represent sister taxa. The Cynognathus Assemblage Zone is characterized by three subzones of differing ages and faunas, with no overlap in the temnospondyls between the subzones.