Skull structure in post-Paleozoic lungfish

ABSTRACT

Three dimensional reconstructions of the dermal skulls of Ceratodus sturii, Ptychoceratodus serratus, Asiatoceratodus (Arganodus) atlantis, and Mioceratodus gregoryi are described, and compared with adult skulls of Recent lungfish of the genera Neoceratodus and Protopterus. Inferred patterns of fusion and reduction of the skull bones of Neoceratodus, Mioceratodus, and Protopterus suggest that these form one natural lineage, excluding Ceratodus, Ptychoceratodus, and Asiatoceratodus. The study of skull roofing bones also indicates that Asiatoceratodus atlantis and Ptychoceratodus serratus are related to each other but not close to other Mesozoic and Cenozoic lungfish, and that Ceratodus sturii is a distinct taxon more distantly associated with other derived dipnoans. The dentitions of the different genera provide unifying characters as all are based on initially isolated cusps that fuse in a pattern of radiating ridges to form tooth plates.