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

Abstract

Chaoceratodus portezuelensis from the Cretaceous of Argentine Patagonia isundergoing re-examination based on both previously known and newly referred toothplates and associated bones. This study expands upon the original diagnosis by incor-porating characteristics specific to pterygopalatine and prearticular tooth plates, anddental histology features. Additionally, it broadens the information based on Mesozoicdipnoans from Patagonia for potential future systematic and phylogenetic studies. Thepterygopalatine tooth plates are characterized by slightly curved mediolingual edges,with the inner angle positioned just behind the second denticulation and short, wide-based first denticulations. The prearticular tooth plates feature mediolingual edgestending towards straight, with the inner angle positioned at the level of the second den-ticulation, short first denticulations, and a bilobed spur. Histological cross-sectionsreveal rows of solid interdenteonal dentine corresponding to ridges that anastomoseover the rest of the plateau. This pattern is visible on the external surface of the toothplates, creating a characteristic wear pattern for the species. Both the morphology andhistology of the dentition bear resemblance, albeit with differences, to other Patago-nian species, such as Metaceratodus baibianorum and Atlantoceratodus iheringi.