Anatomy and relationships of Suterilla Thiele (Caenogastropoda: Assimineidae) with descriptions of four new species

The assimineid genus Suterilla, previously known only from New Zealand, including the Kermadec Islands, is revised using shell, radular and anatomical characters. In addition to the type species S. neozelanica (Murdoch, 1899), four new species are described, S. climoi and S. imperforata from northern New Zealand, S. julieae from northwestern Tasmania and S. fluviatilis from Norfolk Island. All species except the last are found in marine high tidal and supratidal locations, while the Norfolk Island species lives amphibiously in a freshwater stream. These five species are distinguishable chiefly by the characters of the penis and pallial oviduct. A morphology-based cladistic analysis places Suterilla as a primitive member of the subfamily Omphalotropidinae. New information is provided for the amphibious freshwater Tutuilana striata Hubendick, from Samoa, the sister taxon of Suterilla.