Taxonomic Revision of Jingle Shells: Resurrecting and Reclassifying Species of Anomiidae (Bivalvia: Pectinida)

The family Anomiidae exhibits taxonomic ambiguity due to high morphological plasticity and overlapping diagnostic traits. In this study, we resurrect two anomiid species, Heteranomia aculeata and Pododesmus glaucus, and reclassify Isonomia umbonata as Pododesmus umbonatus. Our genetic analyses reveal interspecific cox1 distances between H. aculeata and its former synonym H. squamula, P. glaucus and its synonym P. squama, and P. umbonatus relative to other Pododesmus species. Phylogenetic reconstructions based on five gene fragments (cox1, 16S rRNA, 18S rRNA, 28S rRNA, and histone H3) corroborate the distinction among these previously synonymized species and confirm the placement of P. umbonatus in Pododesmus. Our morphological examinations further delineate diagnostic differences in adductor muscle scars compared to their congeneric species, reinforcing the resurrection and reclassification of these species. Under this reclassification, all Anomiidae genera are monophyletic, with Pododesmus as the earliest-diverging lineage based on available data. However, Placunidae, which contains Placuna as the only genus, is recovered as sister to Anomia, rendering Anomiidae paraphyletic and indicating the need for a taxonomic revision of Placunidae. Additionally, we provide identification keys for the genera Heteranomia and Pododesmus. This study not only highlights the previously underestimated diversity of Anomiidae but also offers essential genetic resources and a refined taxonomic framework, advancing phylogenetic studies of Anomiidae and informing conservation strategies for morphologically complex marine taxa.