Description of new species Macellicephaloides veronikae sp. n. (Polynoidae, Annelida) from the Amundsen Sea, Southern Ocean

While the Southern Ocean represents a unique habitat, currently undergoing rapid environmental change, its biodiversity remains largely unknown, particularly at greater depths. Increased sampling efforts in the Amundsen Sea, a previously unexplored region of the Southern Ocean, combined with the use of an epibenthic sledge resulted in a large collection of mobile, scale-bearing worms from the family Polynoidae Kinberg, 1856. The greatest taxonomic novelty in the material collected from the Pine Island Bay, Amundsen Sea, was found within the exclusively deep-sea subfamily Macellicephalinae Hartmann-Schröder, 1971. Examination of this material has already led to formalization of six new species of <i>Macellicephala</i> (Neal et al. 2018). This study represents the continuation of such effort with formalization of <i>Macellicephaloides veronikae</i> sp. n. based on morphology and 16S and 18S molecular markers. In the phylogenetic analyses, the new species is sister taxon to <i>Macellicephaloides moustachu</i> from the abyssal equatorial Pacific Ocean, albeit based on very limited taxon sampling currently available. <i>Macellicephaloides veronikae</i> sp. n. shows the shallowest distribution (500-1000 m) of this genus recorded to date and may represent a case of polar emergence.