Pleurotomarioidea represents a truly isolated and basally diverging lineage in Vetigastropoda (Mollusca: Gastropoda) whose fossil record can date back to the late Cambrian, thus providing rare insights into the evolutionary history of molluscs. Here, we sequenced and assembled the complete mitochondrial genome of one representative species from Pleurotomarioidea—Entemnotrochus rumphii (Schepman, 1879)—of which the mitogenome is 15,795 bp in length, including 13 protein-coding genes, two ribosomal RNA genes, and 22 transfer RNA genes. The nucleotide composition was biased toward AT, and A + T content reached 65.2%. E. rumphii was recovered as sister to all other living vetigastropods according to mitogenome-based phylogenetic analysis. The mitochondrial gene order was consistent with major vetigastropods and the hypothetical ancestral gastropoda, suggesting the deep conservation of mitogenome arrangement in Vetigastropoda.

Crassostrea ariakensis (Fujita, 1913) is one of the most important economic and ecological oysters that is naturally distributed along the coast of Asia, separated by the Yangtze River estuary. They are usually compared as different populations, while there is no consensus on whether C. ariakensis in northern and southern areas should be considered as two species or subspecies. Here, we analyzed morphological characteristics, COI, 16s rRNA, mitogenome sequences, and species delimitation analysis (ASAP and PTP) to resolve the intraspecific taxonomic status of the C. ariakensis. Phylogenetic and ASAP analysis highlight that C. ariakensis was divided into N-type and S-type. PTP was unable to differentiate between the two types of C. ariakensis. The divergence time of N-type and S-type C. ariakinsis is estimated to be 1.6 Mya, using the relaxed uncorrelated lognormal clock method. Additionally, significant morphological differences exist between the two groups in terms of the adductor muscle scar color. Despite these differences, the COI (0.6%) and 16S rRNA (0.6%) genetic distance differences between N-type and S-type C. ariakensis has not yet reached the interspecific level. These results suggest that N-type and S-type C. ariakensis should be treated as different subspecies and renamed as C. ariakensis ariakensis subsp. nov and C. ariakensis meridioyangtzensis subsp. nov.

The genus Siphonaria G

The family Glauconomidae has few species, limited molecular data description, and insufficient research attention. The biodiversity of Glauconomidae within China deserves further exploration. In recent years, the taxonomic status of Glauconomidae has undergone changes, and some studies have found a close relationship between Glauconomidae and the family Cyrenidae based on molecular data, suggesting that Glauconomidae should be classified under the superfamily Cyrenoidea. However, both domestic and international research has mainly focused on only four species of Glauconomidae, indicating an urgent need for more species data support. Recently, 46 specimens of Glauconomidae were collected in the Yellow River Estuary in Dongying City of Shandong Province in China. Through a comparative analysis of shell morphology and molecular phylogenetic analysis of COI and 16S rRNA, two species of Glauconomidae was discovered. One is Glauconome angulata Reeve, 1844, and the other is a new species of Glauconomidae found in the Yellow River, named Glauconome huangheensis sp. nov. The G. huangheensis sp. nov. exhibits distinct differences in shell shape and shell color compared to other species of Glauconomidae, resembling G. angulata. There are also significant differences in shell color, shell sculpture, ligament size, and shell thickness. Furthermore, the molecular phylogenetic analysis based on COI and 16S rRNA genes supports the validity of G. huangheensis sp. nov. as a species. It indicates a close phylogenetic relationship with G. angulata, making them sister species. This study provides a redescription of the morphological characteristics of G. angulata and G. huangheensis sp. nov., laying the foundation for the morphological classification, biodiversity research, and conservation of Glauconomidae species.