INOUE, J. G.; MIYA, M.; TSUKAMOTO, K.; NISHIDA, M.; Ocean Res. Inst., Univ. of Tokyo; Nat. Hist. Mus. Inst., Chiba; Ocean Res. Inst., Univ. of Tokyo; Ocean Res. Inst., Univ. of Tokyo: Basal Actinopterygian Relationships: A Mitogenomic Perspective on the Phylogeny of the �Ancient Fish�

The basal actinopterygians comprise four major lineages (polypteriforms, acipenseriforms, lepisosteids, and Amia) and have been collectively called �ancient fish.� Although they have been consistently accepted by previous investigators as occupying the most basal positions in the actinopterygian phylogeny, there still remained considerable controversies over their phylogenies in relation to the teleosts. This study attempted to resolve the phylogenetic questions about the ancient fish relationships using complete mitochondrial DNA data with extensive taxonomic sampling. To address this problem, we determined the complete mitochondrial DNA sequences for 18 purposefully-chosen species of actinopterygians (9 basal actinopterygians plus 9 basal teleosts), in addition to 8 euteleosts and 2 outgroups (total 28 spp.), and the data were subjected to phylogenetic analyses. The mitogenomic data strongly supported not only the monophyly of the teleosts (osteoglossomorphs and above), but also a sister-group relationship between the teleosts and a clade comprising the acipenseriforms, lepisosteids, and Amia, with the polypteriforms occupying the most basal position in the actinopterygian phylogeny. Although the tree topology differed from any of the previously-proposed hypotheses based on morphology, it exhibited congruence with a recently-proposed novel hypothesis based on nuclear markers.