Two new species of Capitellidae (Annelida, Polychaeta) from the southern coasts of China

The annelid family Capitellidae Grube, 1862 remains poorly known in China, with only a few taxa reported to date. Based on specimens collected from coastal zones during recent ecological surveys, we describe two new species belonging to two small genera of Capitellidae. Barantolla multibranchia sp. nov. is superficially similar to B. sculpta Southern, 1921 in bearing dorsal branchiae on the posterior abdomen, a complete chaetiger 1, and an areolated epithelium on the anterior thorax, but it differs from the latter in having mixed chaetae in both rami of chaetiger 6 and in lacking cuticular sculpturing.

Parheteromastus simplex sp. nov. represents the second species in this small genus. It resembles its congener in lacking branchiae and in having reduced parapodial lobes in the abdomen but differs in possessing an areolated epithelium extending from the peristomium to chaetiger 3, a distinct constriction between the thorax and abdomen, and a short prostomial palpode. Multiple gene markers and methyl green staining patterns are provided for both species.

Notably, B. multibranchia sp. nov. exhibited intraspecific divergence in COI sequences among collection localities.