A new species of Thoracophelia (Annelida, Opheliidae) from the Yellow Sea of South Korea

A new species, <i>Thoracopheliafoliformis</i> sp. nov., was discovered in the intertidal zone of the Yellow Sea, South Korea. This is the first <i>Thoracophelia</i> species report from the Yellow Sea. This new species is closely related to <i>T.dillonensis</i> (Hartman, 1938) from California and <i>T.ezoensis</i> Okuda, 1936 from Japan in having pectinate branchiae. However, the new species can be distinguished from the two species by the unique combination of the following characteristics: 15 pairs of wrinkled pectinate branchiae with 12-15 filaments at best development and a foliaceous mid-ventral plate in the pygidium instead of one or two thick ventral cirri. Detailed descriptions and illustrations of <i>T.foliformis</i> sp. nov. are provided. Sequences of the mitochondrial cytochrome c oxidase subunit I (COI), nuclear 18S ribosomal DNA (rDNA) and 28S rDNA of the new species were determined and analysed.