Synallactesmcdanieli sp. nov., a new species of sea cucumber from British Columbia, Canada and the Gulf of Alaska, USA (Holothuroidea, Synallactida).

Background: The family Synallactidae comprises mostly deep-sea forms and is the least-studied large taxon amongst deep-sea cucumbers. They are part of the abyssal megafauna and play an important role in modifying the sediment landscape and structuring the communities that live within it. The family embraces the genus Synallactes, which contains approximately twenty-five species from the Pacific, Atlantic (six species), Indian (seven species) and Antarctic Oceans (one species).

New information: Synallactesmcdanieli sp. nov. is described from the Northeast Pacific, Knight Inlet, British Columbia, Canada to Kodiak Island, Gulf of Alaska, USA, at depths from 21 to 438 m. This new species is unique amongst the species of the genus Synallactes because of the number and arrangement of dorsal papillae, number of Polian vesicles, together with the entire ossicle arrangement. In addition, this species has the shallowest bathymetric distribution ever recorded for this genus.