A lower Cynognathus assemblage zone fossil from the Katberg Formation (Beaufort Group, South Africa)

The rocks of the Karoo Supergroup of South Africa accumulated in a retro-fo reland basin in southwestern Gondwana, and contain one of the best-exposed sequences of non-marine Triassic strata in the world.(1) This sequence is f urther renowned for its wealth of terrestrial tetrapod fossils, which have permitted the biostratigraphic subdivision of these rocks.(2) The uppermost biozones of the Beaufort Group in south Africa, the Lystrosaurus and overl ying Cynognathus assemblage zones, provide one of the best records in the w orld of Early to Mid-Triassic terrestrial life and have been considered the type sequence of Early to Mid-Triassic terrestrial faunas.(3) Although the faunas of these two biozones are well known, the interval separating them was believed to be barren of tetrapod fossils,(4) with no representatives o f the Lystrosaurus Assemblage Zone continuing into the Cynognathus Assembla ge Zone.(5,6) Recent investigation of the contact between the two biozones led to the recognition of a fossil fauna in strata previously considered to be barren. These new finds have important implications for the biostratigr aphy, global correlation, biozone ages and Triassic development of the Karo o Basin.