Chaetae A chaetal shaft homogomph articulation Perinereis vallata spiniger NMV F53971 B chaetal shaft heterogomph articulation Perinereis vallata falciger NMV F53971 (= long-bossed heterogomph sensu Conde-Vela (2021) filled arrow points to boss C chaetal shaft sesquigomph articulation Ceratonereis mirabilis (= short-bossed heterogomph sensu Conde-Vela (2021) filled arrow points to boss D heterogomph falcigers with long blades (a < b; = Type 0 of Bakken and Wilson (2005)) E heterogomph falcigers with extra-long blades (2× a < b; = Type 1 of Bakken and Wilson (2005)) F heterogomph falcigers with short blades (a ≥ b; = Type 2 of Bakken and Wilson (2005)) G heterogomph falciger blade with straight margin H heterogomph falciger blade with bowed margin I fused heterogomph falciger chaetiger 70 Hediste diversicolor complex AHF, Gilleleje, Denmark J fused falciger chaetiger 40 Simplisetia aequisetis NMV F53970 K homogomph falciger with terminal tendon (filled arrow) and with terminal secondary tooth (open arrow; = bifid) Platynereis antipoda notopodial falciger chaetiger 66 NMV F50116 L sesquigomph falciger with terminal tendon absent but bifid with secondary terminal tooth (open arrow) and boss (filled arrow) Ceratonereis mirabilis median chaetiger M homogomph falciger with smooth blade Nereis cirriseta chaetiger 74 N homogomph falcigers with bidentate blade and large adjacent terminal and subterminal teeth Nereis bifida chaetiger 71 O homogomph falciger with bidentate blade and large widely-separated terminal and subterminal teeth Nereis triangularis chaetiger 24 P homogomph falciger with multidentate blade with ≥ 2 large lateral teeth, first lateral tooth subequal to terminal tooth, subsequent teeth decreasing in size Nereis denhamensis anterior chaetiger Q homogomph falciger with multidentate blade with ≥ 2 small lateral teeth, first and subsequent lateral teeth much smaller than terminal tooth Nereis apalie chaetiger 74. Sources: A–F, I–K, M–J R. Wilson drawings G, H edited after Villalobos-Guerrero et al. (2021: fig. 1e, f) L after Perkins (1980: fig. 1d) M–P redrawn after Hutchings and Turvey (1982) Q after Wilson (1985: fig. 1E). Not to scale; maximum widths of chaetal shafts (at articulation) are in the range 0.01–0.03 mm.