Two new species of the genus Herpyllobius Steenstrup and Lütken, 1861, H. vanhoeffeni, and H. luetzeni are described associated with polynoid polychaetes collected during the EASIZ III cruise in the Bransfield Strait, Antarctic Peninsula. New records of Herpyllobius antarcticus Vanhöffen, 1913, and H. polarsterni López-González et al., 2000 from Antarctic Peninsula and Eastern Weddell Sea are also given. Including the present records, 17 species of Herpyllobius are now known, 11 of which having been reported from the Southern Hemisphere. The ordinal position of the Herpyllobiidae is discussed according to phylogenetic inferences from the antennular ontogenetic features of the copepodid males of two of the three known genera in the family, Herpyllobius and Eurysilenium Sars, 1870.