Nymphon australe is the most frequently collected of all pycnogonid species in Antarctic area (Munilla & Soler-Membrives, 2009) and in the highest numbers (Arango et al, 2010). It is considered circumpolar and eurybathic, found in most Antarctic and subantarctic benthic collections. As most of pycnogonids Nymphon australe lacks a planktonic stage (Arnaud & Bamber, 1987). Thus, it is of interest to understand how these marine organisms with an apparent limited dispersal capacity have achieved such wide geographical and bathymetric distributions. N. australe is classified within a group of Southern Ocean species of Nymphon sharing few morphological characters such as inflated ovigers, a robust body and setae present on trunk and legs. This group of species or 'australe-complex', is to be tested in a phylogenetic context using both morphology and molecular data to understand the diversification of the group, their relationships to other Antarctic (~60 spp.) species and also the evolutionary history of the cosmopolitan Nymphon (~270 spp.) (Arango et al., 2010).