Comparative figure of form of enlarged branchiae from chaetiger 5 showing variation in development of long branchial filaments, Ms – Main stalk, Lb – lateral branches, Lf – long filaments A Bathychloeia cf. sibogae CCZ specimen, NHMUK ANEA.2022.633, in lateral view B Bathychloeia cf. sibogae CCZ specimen, NHMUK ANEA.2022.634, specimen stained with Shirlastain, in dorsal view C Bathychloeia cf. sibogae South Pacific specimen NHM_215 in dorsal view D Bathychloeia sibogae after Horst (1912) E Bathychloeia sibogae after Böggemann (2009). Scale bars: 1 mm.