Neritopsidae

Abstract: The paleoaustral genus Protodolium Wilckens, 1922, was an important element in the gastropod fauna of the western sector of the Gondwana Realm during Campanian to Maastrichtian time (Late Cretaceous). Previously thought to be endemic to New Zealand, Protodolium is now recognised in inferred Campanian rocks of New Caledonia for the first time, and also in uppermost Cretaceous rocks of Chatham Islands, Southwest Pacific. As a result of renewed interest in Protodolium which has not been studied in any detail for 70 years, a new species has come to light, Protodolium pittensis, described here from the Kahuitara Tuff, Pitt Island, Chatham Islands. Long believed to be a member of Tonnidae (Tonnacea), Protodolium is now reallocated to Neritopsidae (Neritacea). Protodolium species, previously thought to be carnivores, were probably epifaunal herbivores in the littoral to sublittoral zone shallower than mid shelf.

Abstract: A well-supported phylogeny of the Neritopsina, a gastropod superorder archaic in origin, radiated ecologically and diverse in morphology, is reconstructed based on partial 28S rRNA sequences. The result (Neritopsidae (Hydrocenidae (Helicinidae + Neritiliidae) (Neritidae + Phenacolepadidae))) is highly congruent with the fossil records and the character distribution of reproductive tracts in extant taxa. We suggest that the Neritopsina originated in subtidal shallow waters, invaded the land and became fully terrestrial at least three times in different clades, by the extinct Dawsonellidae in the Late Palaeozoic and by the Helicinidae and Hydrocenidae in the Mesozoic. Invasion of fresh- and brackish waters is prevalent among the Neritopsina as the Jurassic and freshwater ancestory is most probable for helicinids. The Phenacolepadidae, a group exclusively inhabiting dysoxic environments, colonized deep-sea hydrothermal vents and seeps in the Late Cretaceous or Early Cenozoic. Submarine caves have served as refuges for the archaic Neritopsidae since the Early to Middle Cenozoic, and the marine neritopsine slug Titiscania represents a highly specialized but relatively recent offshoot of this family. The Neritiliidae is another clade to be found utilizing submarine caves as shelter by the Oligocene; once adapted to the completely dark environment, but some neritiliids have immigrated to surface freshwater habitats.