The comparative osteology and phylogenetic relationships of African and South American lungfishes (Sarcopterygii: Dipnoi)

Abstract

Lepidosirenidae is a clade of freshwater lungfishes that include the extant South American Lepidosiren paradoxaFitzinger, 1837 and African species of the genus Protopterus. These genera have been geographically separated since the break-up of Gondwana in the Early Cretaceous, but they display similar biology and morphology. Species were distinguished by a combination of features such as head-to-body ratios, the number of pairs of ribs, and the presence of external gills, but no discrete skeletal characters were identified, and no comparative studies including all extant species have been published. I used computed tomography (CT), X-ray photography, and specimens from museum collections to describe the skeletal morphology of all species of lepidosirenid in a comparative context. I digitally disarticulated the bones in each specimen to compile a comparative atlas of the cranial and pectoral elements of all extant lungfishes, which has the potential to increase the correct identifications of specimens in museum collections. The morphology of the frontoparietal, parasphenoid, supraorbital, and suboperculum differ between species. I used those characters, along with molecular sequence data from the ribosomal RNA gene 16S, to run combined morphological and molecular phylogenetic analyses. Lepidosirenidae is monophyletic in all analyses, but the interrelationships of the species of Protopterus vary with the different sources of character data.