Ampharetidae Malmgren, 1866 is a polychaete family of deposit-feeder species that flourishes in terms of individuals/m2 and species richness in areas where large quantities of food may accumulate, such as Arctic and Antarctic fjords. Despite the common occurrence of ampharetids in benthic samples and their important ecological role, the nomenclatural status of several species and subspecies is unclear and a general revision of the family is highly needed. In this contribution we focus on the ampharetid genus Amphicteis Grube, 1850, assessing the status of the species currently included in it and describing a new one, Amphicteis teresae sp. nov., collected at Terra Nova Bay (Ross Sea, Antarctica). The new species has blunt and stout paleal chaetae, a feature that is known to occur only in northern hemisphere Amphicteis counterparts. The new species closely resemble the Arctic A. ninonae Jirkov, 1985, to which it could also be phylogenetically related. The morphological re-analysis of the Amphicteis taxa showed that the subspecies of the purportedly cosmopolitan A. gunneri (M. Sars, 1835), which were mainly based on a geographical criterion, represent valid species. Molecular data will indeed be needed to define phylogeographic relationships within this widespread genus.
