A new species of the mysterious genus Spirodiscus (Annelida: Serpulidae) of the eastern Australian abyss

In May–June 2017 an expedition on board RV Investigator sampled benthic communities along the lower slope and abyss of Australia’s eastern margin from off mid-Tasmania to Coral Sea. Over 200 annelids family Serpulidae collected during voyage were deposited in Australian Museum Sydney. Among them there was a new species poorly known abyssal (3754–4378 m) genus Spirodiscus. Serpulids typically build cylindrical calcareous tubes attached hard substrates. Until now, only three serpulid inhabiting free-lying polygonal reported deep sea: Spirodiscus grimaldii Fauvel, 1909 with quadrangular spirally coiled tubes, Bathyditrupa hovei Kupriyanova, 1993 tusk-shaped groenlandicus (McIntosh, 1877) octagonal tubes. The species, S. ottofinamusi sp. nov. has very characteristic thin unattached fluted similar those found groenlandicus, but it differs by details collar, thoracic tori abdominal chaetae. Morphologically, pinnulated opercular peduncle flat geniculate chaetae like filogranin serpulids lacks Apomatus serpulins. first DNA sequences this mysterious taxon places within filogranins sister group relationship Chitinopoma serrula.