Late Triassic Dipnoi from south Gondwana, Rio Grande do Sul, Brazil

Mesozoic lungfishes are often represented in the fossil record by isolated tooth plates, which impose limitations on their taxonomic identification and on the interpretation of their diversity. In the Triassic of South America, these organisms remain poorly documented. The present study describes eight isolated tooth plates from the Candelária Sequence of the Santa Maria Supersequence (Carnian, Late Triassic), southern Brazil, being attributed to three taxa: Ptychoceratodus phillipsi , P. eliseui sp. nov., and Ferganoceratodus cabreirai sp. nov. The description was made using morphological and morphometric approaches and the tooth plates. The results highlight the strong morphological similarity between Ptychoceratodus and Ferganoceratodus , as well as the overlap of diagnostic characters, which reinforces the difficulties in distinguishing between these genera when only isolated tooth plates are available. The association with other ichthyofauna and the presence of deposits indicative of varying depositional energies suggest a seasonal environment, with alternation between wet and dry periods. From a paleobiogeographic perspective, the record of Ferganoceratodus represents the first occurrence of the genus in the Triassic of South America, extending its previously known distribution. The occurrence of P. phillipsi , in turn, reinforces the wide dispersal of lungfishes throughout Pangaea during the Mesozoic. In this context, the materials described herein represent a relevant contribution to the Gondwanan record of Mesozoic lungfishes and reinforce the importance of the Candelária Sequence as a key unit for Triassic dipnoan paleobiogeography and biostratigraphy. The occurrence of these genera in Brazilian continental deposits is consistent with the distribution pattern observed for Mesozoic lungfishes and suggests faunal affinities with assemblages from other portions of Gondwana.