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 Macellicephala (Neal et al. 2018). This study represents the continuation of such effort with formalization of Macellicephaloides veronikae sp. n. based on morphology and 16S and 18S molecular markers. In the phylogenetic analyses, the new species is sister taxon to Macellicephaloides moustachu from the abyssal equatorial Pacific Ocean, albeit based on very limited taxon sampling currently available. Macellicephaloides veronikae sp. n. shows the shallowest distribution (500-1000 m) of this genus recorded to date and may represent a case of polar emergence.