The marine gastropod Strombidae is widely distributed in tropical and subtropical regions all over the world and possesses high morphological diversity. In order to better understand how morphological characteristics evolved within Strombidae, a robust phylogenetic framework is needed. In the present study, the complete mitochondrial genomes of Lentigo lentiginosus, Euprotomus aratrum, and Canarium labiatum were sequenced. The three newly sequenced mt genomes contained 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, two ribosomal RNA (rRNA) genes, and several non-coding regions, indicating a similar pattern with respect to genome size, gene order, and nucleotide composition compared with those of other strombids reported before. Two different datasets derived from mitochondrial genes were constructed to resolve the internal phylogenetic relationships of Stromboidea and Strombidae. Within Stromboidea, the sister group formed by Clade I [Rostellariidae + (Seraphsidae + Strombidae)] and Clade II [Xenophoridae + (Struthiolariidae + Aporrhaidae)] were fully recovered and supported by morphological synapomorphies as previously suggested. The phylogenetic positions of L. lentiginosus, E. aratrum, and C. labiatum were confirmed within Strombidae, and several morphological similarities were observed corresponding to the present phylogeny. A correlation between strombids speciation events and paleoclimate change was presumed. Our results indicate that complete mt genomes would be a promising tool to reconstruct a robust phylogeny of Strombidae with an increased taxon sampling in the future.

Cowries (Family Cypraeidae) are widely distributed in tropical and subtropical seas, with the highest diversity of cowries in the Indo-Pacific region. However, the classification of Cypraeidae, especially at the lower taxonomic levels, is still controversial. In the present study, we determined the complete mitochondrial genomes of 10 cowries. All the newly sequenced mtDNA encode 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, two ribosomal RNA (rRNA) genes, and several non-coding regions. The reconstructed mitogenomic phylogeny of Cypraeidae recognized two monophyletic clades, with the first clade comprised of Erroneinae, Cypraeinae and Luriinae and the second clade formed by the single subfamily Erosarinae. The congeneric genetic distance values fall within 0.118–0.144, lower than those above genus level ranging from 0.163 to 0.271, consistent with the current division of genera within Cypraeidae. The divergence time estimated here indicated that the ancestor of Indo-Pacific cowries diversified during the Paleocene, and the closure of the Tethys Seaway might lead to the speciation events of several Indo-Pacific species. This study suggests that the complete mtDNA is a promising tool to improve the phylogenetic resolution of Cypraeidae, and mtDNA could also provide important information for future species delimitation especially within the cowries that possess different morphological phenotypes.