SEM photographs of Promastobranchus variabilis sp. nov., paratype (TIO-BTS-Poly144) A anterior 13 chaetigers B anterior end, ventro-lateral view C transition between thorax and abdomen, lateral view D genital pore on between chaetigers 11/12, lateral view E posterior end showing neuropodia, ventral view F abdominal hooks at chaetiger 16 G ultrastructure of hooks. Abbreviations: cc, capillary chaetae; gp, genital pore; hh, hooded hook; mf, main fang; neu, neuropodia; per, peristomium. Scale bars: 200 μm (A–E); 20 μm (F); 5 μm (G).