Obscuranella papyrodes, a new genus and species of abyssal tonnoidean gastropod from Antarctica

Abstract

The new genus Obscuranella and O. papyrodes, its type species, are described from the abyssal plain off the Ross Sea, Antarctica. Obscuranella is included in the primarily tropical, shallow water superfamily Tonnoidea because it has a taenioglossan radula, extensible proboscis, large salivary glands composed of anterior and posterior lobes, salivary ducts that pass through the nerve ring, and an undifferentiated oesophageal gland. This taxon is precluded from the families Laubierinidae, Pisanianuridae, and Tonnidae because it lacks a monopectinate osphradium, paired proboscis retractor muscles passing through the nerve ring, buccal glands, and rachidian teeth with lateral basal denticles. Obscuranella is assigned to the family Ranellidae primarily on the basis of shell, radular, and opercular morphology. This is the first report of the Tonnoidea in Antarctic waters, and the first record of Ranellidae from abyssal depths.