A molecular approach to systematics of Polypteriformes among Osteichthyes

The Sarcopterygii are considered to be the living species most closely related to the ancestors of the tetrapods: they include the extinct rhipidistians, the coelacanths and the dipnoans. Furthermore, many Authors debate whether the Polypteriformes should be assigned a very peculiar place in the phylogeny of the bony fishes. To investigate the group of Polypteriformes and the Dipnoans and to provide new support for the classic morphological and molecular data and previous karyological evidence, we examined the DNA sequences of the mitochondrial genes 16S, 12S and cyt-b in two polypterids (Polypterus palmas and Erpetoichthys calabaricus) and two lungfish (Protopterus annectens and P. aethiopicus). In all the trees, Polypteriformes and Dipnoi are grouped together, while coelacanths remain as a sister group of these two. This molecular evidence supports the earliest hypotheses in which Polypteriformes were grouped in the same subclass together with the coelacanths and Dipnoi.