Two new species of Ischnomesidae (Crustacea: Isopoda) from the Southern Ocean displaying neoteny

Two new asellote isopod species, Stylomesus hexapodus n. sp. and Haplomesus corniculatus n. sp., are described from samples obtained with an epibenthic sledge in the Southern Ocean deep sea. Both species show the retention of juvenile characters in the adult stages, by the lack of the seventh pair of pereopods, a phenomenon described for the first time for Ischnomesidae.