Fossil lungfishes (Sarcopterygii, Dipnoi) of the Lower Triassic Driefontein locality in the Burgersdorp Formation, Beaufort Group, of South Africa, and their implications for ceratodontiform diversity after the end-Permian mass extinction

The Driefontein locality in the Lower Triassic Burgersdorp Formation (Beaufort Group) of South Africa preserves an assemblage of 103 lungfish tooth plates, three of which are associated with five poorly preserved skull bones, a rare occurrence in strata above the Permian–Triassic boundary (PTB). Most occurrences of lungfishes in the Mesozoic consist of isolated tooth plates, so we document their size, shape, and number of ridges and intervening furrows to test the previous assignment of these plates to Ptychoceratodus . We supplement the morphological characters with principal component and linear discriminant analyses, using measurements of the length and width (in mm) of the plates as well as three angles formed by their ridges. Qualitative observation and our multivariate analyses confirm the presence of three morphs of lungfishes at Driefontein: the pre-established Ptychoceratodus sp., along with cf. Arganodus and cf. Gnathorhiza . Driefontein is the most diverse lungfish locality in Gondwana during the Early Triassic, providing new evidence for the rapid recovery and re-radiation of dipnoans following the PTB. We extend the range of Arganodus into sub-Saharan Africa and report the first occurrence of an African Gnathorhiza , showing that Triassic gnathorhizids were not restricted to Europe before their extinction at the end of the Olenekian. Arganodus and Ptychoceratodus coexisted on at least four modern continents, while Gnathorhiza coexisted with both genera on at least two. Driefontein preserves a uniquely diverse assemblage of vertebrates, including many diminutive individuals, perhaps reflecting an example of re-radiation and the ‘Lilliput effect’ in the aftermath of the Permian extinction.