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, <i>Heteranomia aculeata</i> and <i>Pododesmus glaucus</i>, and reclassify <i>Isonomia umbonata</i> as <i>Pododesmus umbonatus</i>. Our genetic analyses reveal interspecific <i>cox1</i> distances between <i>H. aculeata</i> and its former synonym <i>H. squamula</i>, <i>P. glaucus</i> and its synonym <i>P. squama</i>, and <i>P. umbonatus</i> relative to other <i>Pododesmus</i> species. Phylogenetic reconstructions based on five gene fragments (<i>cox1</i>, <i>16S rRNA</i>, <i>18S rRNA</i>, <i>28S rRNA</i>, and <i>histone H3</i>) corroborate the distinction among these previously synonymized species and confirm the placement of <i>P. umbonatus</i> in <i>Pododesmus</i>. 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 <i>Pododesmus</i> as the earliest-diverging lineage based on available data. However, Placunidae, which contains <i>Placuna</i> as the only genus, is recovered as sister to <i>Anomia</i>, rendering Anomiidae paraphyletic and indicating the need for a taxonomic revision of Placunidae. Additionally, we provide identification keys for the genera <i>Heteranomia</i> and <i>Pododesmus</i>. 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.