New species, anatomy, and systematic position of the hydrothermal vent and hydrocarbon seep gastropod family Provannidae fam.n. (Caenogastropoda)



The anatomy of the hydrothermal vent gastropod Provanna is described. It is shown to be a primitive neotaenioglossan with mainly plesiomorphic features in all systems, including open pallial gonoducts, epiathroid nervous system with accessory pedal ganglia and a circulatory system where a considerable portion of the venous blood from the coelomic spaces enters the pallial skirt. Apomorphic features include the possession of an anterior notch, or short canal in the shell (and mantle edge), an annulated sensory pallial tentacle, paraspermatozoa modificd as nurse cells. multiple seminal receptacles, a posterior bursa copulatrix, and a renal oviduct with three distinct regions. the middle one expanded. Comparisons are madc with Abyssochrysos, a genus assumed to be a relict member of the Loxonematoidea, which appears to be the closest known relative. A new family. Provannidae fam.n., is created and tentatively included in the Loxonematoidea. The following new specics are described: Provanna segonzaci sp.n. (from hydrothermal vents at the Fiji Back Arc), P. laevis sp.n. (from hydrothermal seeps in the Gulf of California), P. sculpta sp.n. and P. admetoides sp.n. (from hydrocarbon seeps in the Gulf of Mexico). New records are added for previously described species of Provanna.