A new species of
Odontosyllis is described herein, together with a description of Brazilian material of
Odontosyllis cf. fulgurans (Audouin and Milne Edwards, 1834) collected along the coast off the State of São Paulo, southeastern Brazil, mostly from rocky shores.
Odontosyllis guillermoi sp. nov. is characterized by its conspicuous pigmentation, consisting of a prostomial “mask” and 2 transverse bands per segment throughout, by the subdistal tooth of the blades of the falcigers being much shorter than the distal one, especially on the posterior chaetigers, and by anterior parapodia having up to 5 aciculae each.