Unveiling the histology and anatomy of the lungfish Chaoceratodus portezuelensis (Sarcopterygii: Dipnoi) from the Portezuelo and Cerro Lisandro formations (Upper Cretaceous) of Argentine Patagonia

Chaoceratodus portezuelensis from the Cretaceous of Argentine Patagonia is undergoing re-examination based on both previously known and newly referred tooth plates and associated bones. This study expands upon the original diagnosis by incorporating characteristics specific to pterygopalatine and prearticular tooth plates, and dental histology features. Additionally, it broadens the information based on Mesozoic dipnoans from Patagonia for potential future systematic and phylogenetic studies. The pterygopalatine tooth plates are characterized by slightly curved mediolingual edges, with the inner angle positioned just behind the second denticulation and short, widebased first denticulations. The prearticular tooth plates feature mediolingual edges tending towards straight, with the inner angle positioned at the level of the second denticulation, short first denticulations, and a bilobed spur. Histological cross-sections reveal rows of solid interdenteonal dentine corresponding to ridges that anastomose over the rest of the plateau. This pattern is visible on the external surface of the tooth plates, creating a characteristic wear pattern for the species. Both the morphology and histology of the dentition bear resemblance, albeit with differences, to other Patagonian species, such as Metaceratodus baibianorum and Atlantoceratodus iheringi.