Potential Cryptic Diversity in the Genus Scoliodon (Carcharhiniformes: Carcharhinidae): Insights from Mitochondrial Genome Sequencing

<i>Scoliodon</i> is a genus of small placental sharks living in offshore waters. For a long time, the genus was considered a monotypic genus until a valid species, <i>Scoliodon macrorhynchos</i>, was confirmed in 2010. However, <i>S. muelleri</i> in the same study was not widely recognized because of the lack of evidence. In this study, we obtained the complete mitochondrial genome of the genus <i>Scoliodon</i> from Ranong, Thailand, and tentatively named it <i>Scoliodon</i> sp. By comparing the complete mitochondrial genome with those of two other <i>Scoliodon</i> species and conducting phylogenetic and divergence time analyses, we determined that <i>Scoliodon</i> sp. diverged from the other species. These findings indicate the potential for a new cryptic species (<i>Scoliodon</i> sp.) in the <i>Scoliodon</i> genus. This conclusion was further supported by a subsequent analysis of the published <i>S. laticaudus</i> control region sequences from previous studies. Finally, based on these conclusions, we used machine learning to derive a new identification method for the cryptic species. This approach may be useful for the discovery of new species or cryptic species in other organisms.