| Summary: | Two new species of Sphaerodoropsis Hartman & Fauchald, 1971 (Polychaeta: Sphaerodoridae), collected during the BIOICE programme on sedimentary bottoms off Iceland, are described. Sphaerodoropsis gudmunduri sp. nov. is a shelf species (<400 m) chiefly characterized by having one transverse row of up to 10–12 dorsal macrotubercles per chaetiger (‘Sphaerodoropsis group 2’) and body papillae present only on the prostomium, peristomium, parapodia and ventral surface. It also has up to 7–9 ventral papillae per chaetiger arranged following a non-random pattern and parapodia which bear one digitiform prechaetal lobe, 1–4 papillae and compound unidentate chaetae with blades with thin spinulation along their cutting edge. Sphaerodoropsis halldori sp. nov. has been found in deeper waters (>1000 m) and may be distinguished mostly by having up to 13 dorsal macrotubercles arranged in two transverse rows (6–7 macrotubercles, respectively) defining a zig-zag pattern (‘group 3’) and 7 dorsal papillae per chaetiger, up to 8–10 ventral papillae per chaetiger arranged in a non-random pattern and parapodia which bear one digitiform prechaetal lobe, one antero-lateral papilla and compound unidentate chaetae with blades with thin spinulation along their cutting edge. Both species show sexual dimorphism characterized by different arrangements of modified ventral cirri and/or special ventral structures in some mid-body chaetigers; a brief discussion about the presence of these structures on sphaerodorids and their possible importance on the systematics of the family is provided.
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