Benthic invertebrates at deep-sea hydrothermal vents and cold seeps have attracted considerable attention regarding their spatiotemporal distributions, colonization pathways, geological origins and morphological, ecological and physiological adaptations. Here we first reconstruct a molecular phylogeny for vent and seep species in the gastropod subclass Neritimorpha based on combined mitochondrial and nuclear gene sequences. The resulting tree, in conjunction with anatomical and palaeontological evidence, indicates that neritimorph snails and limpets in the Cenozoic deep-sea chemosynthetic habitats belong to the monophyletic subfamily Shinkailepadinae (family Phenacolepadidae). Confamilial shallow-water species form its sister clade, the subfamily Phenacolepadinae. There were probably at least three independent shifts from the coiled snail with a functional operculum to the limpet form in the evolutionary history of the family, twice in the deep-sea Shinkailepadinae and once in the shallow-water Phenacolepadinae. Physiological and ecological characteristics including the presence of red blood cells and larval migration seem to have facilitated their early Cenozoic Colonization of vents and seeps. The type specimens of type species were investigated for most nominal genera to amend generic classification of this long-neglected family. A monotypic Divia gen. nov. is proposed for ‘Shinkailepas’ briandi; Shinkailepas and Thalassonerita pre-date Olgasolaris and Bathynerita, respectively;

KAVIENG 2014

Here we report our direct observation in Papua New Guinea (PNG) of three estuarine species of neritid gastropods (Neritimorpha: Neritidae) that survived on driftwood in seawater for some extended period and were transported several kilometres to a fully marine shore. Furthermore, we found another species of typically estuarine Neritidae on sunken pieces of wood at depths of 105–135 m in Vanuatu, South Pacific. These supposedly non marine gastropods evidently have the potential to survive in fully marine conditions and to disperse as benthic adults and eggs. We suggest that driftwood from shallow-water environments, including estuaries, mangrove swamps and mudflats, might have an evolutionary significance for the establishment of the sunken-wood community and possibly other chemosynthetic faunas in the deep sea.

PAPUA NIUGINI, SANTO 2006