A mitochondrial genome phylogeny of Mytilidae (Bivalvia: Mytilida).

•The phylogenetic relationships among subfamilies of the Mytilidae are uncertain.•A mitochondrial genome phylogeny was reconstructed for 27 mytilid species.•The phylogeny shows two major clades that have diverged in the Devonian.•The splitting time among the major subfamilies occurred in the Mesozoic period.