ABSTRACT The assignment of species to the vetigastropod genus Solariella Wood, 1842, and therefore the family Solariellidae Powell, 1951, is complicated by the fact that the type species (Solariella maculata Wood, 1842) is a fossil described from the Upper Pliocene. Assignment of species to genera has proved difficult in the past, and the type genus has sometimes acted as a ‘wastebasket’ for species that cannot easily be referred to another genus. In the light of a new systematic framework provided by two recent publications presenting the first molecular phylogenetic data for the group, we reassess the shell characters that are most useful for delimiting genera. Shell characters were previously thought to be of limited taxonomic value above the species level, but this is far from the case. Although overall shell shape is not a reliable character, our work shows that shell characters, along with radular and anatomical characters, are useful for assigning species to genera. Sculpture of the early teleoconch (the region immediately following the protoconch) and the columella are particularly useful characters that have not been used regularly in the past to distinguish genera. However, even with the combination of all morphological characters used in this study (shell, radular and eye), a few species are still difficult to assign to genera and in such cases molecular systematic data are essential. In the present study, we discuss 13 genera—12 of which were recovered as well-supported clades in recent molecular systematic studies—and provide morphological characters to distinguish them. We describe several new taxa: Chonospeira n. gen. (referred to as ‘clade B’ in previous molecular systematic studies), Phragmomphalina n. gen. (Bathymophila in part in molecular systematic studies) and Phragmomphalina vilvensi n. sp. (type species of Phragmomphalina n. gen.). We synonymize Hazuregyra Shikama, 1962 with Minolia A. Adams, 1860, Minolia subangulata Kuroda & Habe, 1952 with Minolia punctata A. Adams, 1860 and M. gemmulata Kuroda & Habe, 1971 with M. shimajiriensis (MacNeil, 1960). We also present the following new combinations: Bathymophila bairdii (Dall, 1889), B. dawsoni (Marshall, 1979), B. regalis (Marshall, 1999), B. wanganellica (Marshall, 1999), B. ziczac (Kuroda & Habe in Kuroda, Habe & Oyama, 1971), Chonospeira nuda (Dall, 1896), C. iridescens (Habe, 1961), C. ostreion (Vilvens, 2009), C. strobilos (Vilvens, 2009), Elaphriella corona (Lee & Wu, 2001), E. diplax (Marshall, 1999), E. meridiana (Marshall, 1999), E. olivaceostrigata (Schepman, 1908), E. opalina (Shikama & Hayashi, 1977), Ilanga norfolkensis (Marshall, 1999), I. ptykte (Vilvens, 2009), I. zaccaloides (Vilvens, 2009), Minolia shimajiriensis (MacNeil, 1960), M. watanabei (Shikama, 1962), Phragmomphalina alabida (Marshall, 1979), P. diadema (Marshall, 1999), P. tenuiseptum (Marshall, 1999), Spectamen euteium (Vilvens, 2009), S. basilicum (Marshall, 1999), S. exiguum (Marshall, 1999) and S. flavidum (Marshall, 1999).

Yasunori Kano1, Hiroaki Fukumori1,2, Bastian Brenzinger3 and Anders Warén4 Department of Marine Ecosystems Dynamics, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan; Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan; Bavarian State Collection of Zoology, Münchhausenstr. 21, D-81247 Munich, Germany; and Swedish Museum of Natural History, Box 50007, SE-10405 Stockholm, Sweden

Recent expeditions have revealed high levels of biodiversity in the tropical deep-sea, yet little is known about the age or origin of this biodiversity, and large-scale molecular studies are still few in number. In this study, we had access to the largest number of solariellid gastropods ever collected for molecular studies, including many rare and unusual taxa. We used a Bayesian chronogram of these deep-sea gastropods (1) to test the hypothesis that deep-water communities arose onshore, (2) to determine whether Antarctica acted as a source of diversity for deep-water communities elsewhere and (3) to determine how factors like global climate change have affected evolution on the continental slope. We show that although fossil data suggest that solariellid gastropods likely arose in a shallow, tropical environment, interpretation of the molecular data is equivocal with respect to the origin of the group. On the other hand, the molecular data clearly show that Antarctic species sampled represent a recent invasion, rather than a relictual ancestral lineage. We also show that an abrupt period of global warming during the Palaeocene Eocene Thermal Maximum (PETM) leaves no molecular record of change in diversification rate in solariellids and that the group radiated before the PETM. Conversely, there is a substantial, although not significant increase in the rate of diversification of a major clade approximately 33.7 Mya, coinciding with a period of global cooling at the Eocene-Oligocene transition. Increased nutrients made available by contemporaneous changes to erosion, ocean circulation, tectonic events and upwelling may explain increased diversification, suggesting that food availability may have been a factor limiting exploitation of deep-sea habitats. Tectonic events that shaped diversification in reef-associated taxa and deep-water squat lobsters in central Indo-West Pacific were also probably important in the evolution of solariellids during the Oligo-Miocene.

Rubyspira, a new genus of deep-sea snails (Gastropoda: Abyssochrysoidea) with two living species, derives its nutrition from decomposing whalebones. Molecular phylogenetic and morphological evidence places the new genus in an exclusively deep-sea assemblage that includes several close relatives previously known as fossils associated with Cretaceous cold seeps, plesiosaur bones, and Eocene whalebones. The ability to exploit a variety of marine reducing environments may have contributed to the evolutionary longevity of this gastropod lineage.

The Sovanco Fracture Zone and Blanco Transform Fault separate the Explorer, Juan de Fuca, and Gorda ridge systems of the northeastern Pacific Ocean. To test whether such offsets in the ridge axis create barriers to along-axis dispersal of the endemic hydrothermal vent animals, we examined the genetic structure of limpet populations previously identified as Lepetodrilus fucensis McLean, 1988 (Gastropoda, Lepetodrilidae). Mitochondrial DNA sequences and patterns of allozyme variation revealed no evidence that the 150-km-long Sovanco Fracture Zone impeded gene flow between the Explorer and Juan de Fuca populations. In contrast, the 450-km-long Blanco Transform Fault separates the limpets into highly divergent northern and southern lineages that we recognize as distinct species. We describe southern populations from the Gorda Ridge (Seacliff) and Escanaba Trough as Lepetodrilus gordensis new species and refer northern populations from the Explorer and Juan de Fuca ridge systems to L. fucensis sensu stricto. The species are similar morphologically, but L. gordensis lacks a sensory neck papilla and has a more tightly coiled teleconch. To assess the degree of isolation between these closely related species, we used the Isolation with Migration method to estimate the time of population splitting, effective sizes of the ancestral and derived populations, and rates of migration across the Blanco Transform Fault.

Bathymetric gradients of biodiversity in the deep-sea benthos constitute a major class of large-scale biogeographic phenomena. They are typically portrayed and interpreted as variation in alpha diversity (the number of species recovered in individual samples) along depth transects. Here, we examine the depth ranges of deep-sea gastropods and bivalves in the eastern and western North Atlantic. This approach shows that the abyssal molluscan fauna largely represents deeper range extensions for a subset of bathyal species. Most abyssal species have larval dispersal, and adults live at densities that appear to be too low for successful reproduction. These patterns suggest a new explanation for abyssal biodiversity. For many species, bathyal and abyssal populations may form a source-sink system in which abyssal populations are regulated by a balance between chronic extinction arising from vulnerabilities to Allee effects and immigration from bathyal sources. An increased significance of source-sink dynamics with depth may be driven by the exponential decrease in organic carbon flux to the benthos with increasing depth and distance from productive coastal systems. The abyss, which is the largest marine benthic environment, may afford more limited ecological and evolutionary opportunity than the bathyal zone.

About 2,400 names at the rank of subtribe, tribe, subfamily, family and superfamily have been proposed for Recent and fossil gastropods. All names are listed in a nomenclator giving full bibliographical reference, date of publication, type genus, and their nomenclatural availability and validity under the International Code of Zoological Nomenclature. Another 730 names, established for categories above the family-group, and not regulated by the Code, are listed separately. A working classification attempts to reconcile recent advances in the phylogeny of the Gastropoda, using unranked clades above superfamilies, and the more traditional approach, using hierarchical ranking below superfamily. Altogether, the classification recognizes as valid a total of 611 families, of which 202 are known exclusively as fossils and 409 occur in the Recent with or without a fossil record. The nomenclator and classification will be updated in forthcoming editions to be published electronically.

ABSTRACT Here we describe novel forms of structural integration between endo- and episymbiotic microbes and an unusual new species of snail from hydrothermal vents in the Indian Ocean. The snail houses a dense population of γ-proteobacteria within the cells of its greatly enlarged esophageal gland. This tissue setting differs from that of all other vent mollusks, which harbor sulfur-oxidizing endosymbionts in their gills. The significantly reduced digestive tract, the isotopic signatures of the snail tissues, and the presence of internal bacteria suggest a dependence on chemoautotrophy for nutrition. Most notably, this snail is unique in having a dense coat of mineralized scales covering the sides of its foot, a feature seen in no other living metazoan. The scales are coated with iron sulfides (pyrite and greigite) and heavily colonized by ε- and δ-proteobacteria, likely participating in mineralization of the sclerites. This novel metazoan-microbial collaboration illustrates the great potential of organismal adaptation in chemically and physically challenging deep-sea environments.

1, C and D). The dominant crystalline mineral phase is pyrite, whereas greigite, the sulfide analog of magnetite, is present in lower proportions and accounts for the ferrimagnetism. The interior of the sclerites is penetrated by a pulp of pedal tissue that extends almost to the tip. Between the pulp and the outer mineralized layers there is a tough, laminated, organic layer, histologically indistinguishable from molluscan conchiolin. The conchiolin is studded with minute (typically about 1 m in diameter) iron sulfide granules and finely dispersed iron sulfur compounds; these minerals are more common in the outer layers of the conchiolin. Where the sclerite surface is overlain by adjacent sclerites, the sclerites are covered by a coat of bacteria (Fig. 1C; fig. S2G). Iron sulfide as a skeletal material is not known in metazoans (4), although accumulations of metal sulfides occur in animal tissues

A monoplacophoran species and about 100 species of gastropods are recorded from hydrothermal vents and various kinds of seeps from the Atlantic and Pacific Oceans. Previously described species are supplemented with new information on distribution, ecology, morphology, and systematics. The zoogeography of these faunas is discussed and it is noticed that there is a good resemblance in generic composition between the vent and seep localities, while the species usually occur in only one of the two environments. More than 95% of the species found in vents have not been found outside this environment, and the endemic species make up more than 99.5% of the individuals. The fauna of the seeps is less well demarcated. Two species of Provanna (Caenogastropoda, Provannidae) are recorded from sunken drift wood in the NE Pacific. The genus was previously thought to be endemic to vent and seep environments. The fauna of the recently investigated vent system at the East Pacific Rise, 17 degrees S is very similar to that of the more northern (9-21 degrees N) localities; 14 species out of 16 are shared. Available evidence for a hypothesized relict character of the gastropod fauna is evaluated and failed to support the hypothesis. Spermatophores were found in Melanodrymia sp., the first known case in Neomphalina. A possible case of imposer is reported from the conid genus Phymorhynchus. The first monoplacophoran from hydrothermal vents is described, Rokopella segonzaci, sp. nov. (Family Neopilinidae), from the Mid-Atlantic Ridge at about 38 degrees N.The following new gastropod taxa are described. Patellogastropoda. Family Neolepetopsidae: Paralepetopsis ferrugivora, sp. nov., from the Mid-Atlantic Ridge, 37 degrees N; P. lepichoni, sp. nov., from the Nankai Trough off south-eastern Honshu, Japan. Vetigastropoda. Family uncertain: Adeuomphalus trochanter, sp. nov., from the Juan de Fuca Ridge; Sahlingia xandaros, gen. et sp. nov., from the Aleutian Trench. Family Lepetodrilidae: Lepetodrilus atlanticus, sp. nov., from the Mid Atlantic Ridge, 23-38 degrees N. Family Sutilizonidae: Sutilizona pterodon, sp. nov., from the Mid-Atlantic Ridge, 23 degrees N; S. tunnicliffae, sp. nov., from the Juan de Fuca Ridge. Skeneidae: Bruceiella athlia, sp, nov., from seeps in the Aleutian Trench. Trochidae: Falsimargarita nauduri, sp. nov., from vents at the East Pacific Rise at 17 degrees S; Fucaria mystax, sp. nov., from vents off eastern New Guinea. Uncertain position. Family Neomphalidae: Melanodrymia galeronae, sp, nov., from the East Pacific Rise at 13 degrees N; Retiskenea diploura, gen. ct sp. nov., from the Aleutian Trench; Lacunoides vitreus, sp. nov., from the Juan de Fuca Ridge. Family Peltospiridae: Lirapex costellata, sp. nov., from the Mid-Atlantic Ridge at 37 degrees N; Nodopelta rigneae, sp. nov., from the East Pacific Rise at 13 degrees N; Peltospira smaragdina, so. nov., from the Mid-Atlantic Ridge, 15-38 degrees N. Depressigyra? statura Goedert & Benham, 1999, from Eocene seep deposits in the state of Washington is transferred to Retiskenea. Neritimorpha. Family Phenacolepadidae: Shinkailepas briandi, sp. nov., from the Mid-Atlantic Ridge, 15-38 degrees N. Caenogastropoda. Family Cerithiopsidae: Speculator cariosus, gen. ct sp, nov. from the Juan de Fuca Ridge. Family Vitrinellidae: Neusas, gen. nov., marshalli (Sykes, 1925), from the bathyal Northeast Atlantic. Family Elachisinidae: Laeviphitus desbruyeresi, sp. nov., from the Mid-Atlantic Ridge, 37 degrees N. Buccinidae: Bayerius peruvianus, sp. nov., from seeps off Peru; Eosipho auzendei, sp. nov., from vents at the East Pacific Rise at 17 degrees S. Conidae: Bathybela papyracea, sp. nov., from Gulf of California, off Jalisco; Phymorhynchus major, sp. nov., from the East Pacific Rise at 13 degrees N; P. carinatus, sp. nov., from the Mid-Atlantic Ridge, 15-23 degrees N; P. ovatus, sp. nov., from the Mid-Atlantic Ridge, 15-37 degrees N. Heterobranchia. Family Hyalogyrinidae: Hyalogyrina globularis, sp. nov., from the Juan de Fuca Ridge; H. umbellifera, sp. nov., from seeps in the Aleutian Trench. Family Orbitestellidae: Lurifax vitreus, gen. et sp. nov., from the Mid-Atlantic Ridge, 37-38 degrees N. Family Xylodisculidae: Xylodiscula analoga, sp. nov., from the Mid-Atlantic Ridge, 37 degrees N.

La campagne BORDAU 1, realisee a bord du N. O. Alis, s'est deroulee dans les eaux des Fidji, du 22 fevrier au 14 mars 1999. Cent dix-huit operations de dragages et de chalutages ont eu lieu dans les zones bathyale superieure et circalittorale des iles et sur les monts sous-marins de la ride de Lau. La partie superieure des pentes presente des fonds rocheux jusqu'a 600 m de profondeur. Plus profondement, on retrouve les fonds envases couverts de pierres ponces. Dans certaines iles particulierement isolees (Vanua Balavu, Yacata, Aiwa et Yagasa), un echantillonnage de la malacofaune terrestre a ete realise.

La position systematique du gastropode Retrotortina fuscata se trouve confirmee dans la famille des Omalogyridae. Son habitat se situe dans des sables bioclastiques grossiers vers 10-30 m de profondeur, et sa distribution s'etend de l'entree occidentale de la Manche, jusqu'en Mediterranee occidentale. C'est une espece nouvelle pour la faune de France, et une mention ancienne pour les Iles Britanniques parait de ce fait vraisemblable.

Five, possibly six, north European species are confirmed in the prosobranch genera Rissoa and Pusillina: R. parva (Da Costa); R. lilacina Récluz; R. membranacea (Adams) (types A & B); P. inconspicua (Alder) and P. sarsi (Lovén). The five species differ ecologically in salinity tolerances, with R. membranacea and P. sarsi being the most tolerant and regularly occurring at salinities of 7–10% 0 , while R. parva, R. lilacina , and P. inconspicua tolerate salinities down to 20% 0 (for shorter periods 15% 0 ). There are also differences in the ability to survive occasional, short exposures to highly reduced salinity with 50% survival for R. membranacea after 80 h; R. lilacina , 30 h; P. sarsi , 25–30 h; and for P. inconspicua after 15 h exposure to freshwater at 8°C. At higher temperatures the survival is lower. There is a difference in the requirements on water circulation, with R. parva and R. lilacina preferring more current-swept and exposed environments. Rissoa membranacea occurs in two types, possibly species, with planktotrophic and lecithotrophic larval development respectively. In Scandinavia, populations with lecithotrophic development have a restricted occurrence between Sjaelland and Jylland in Denmark, but may be more common in the UK and France. Such specimens are always accompanied by the planktotrophic form, and it can not be excluded that the two forms are conspecific and this is a case of poecilogony. There is also a possibility that P. sarsi actually constitutes a series of populations of P. inconspicua adapted to local, more brackish conditions by larger egg size and veligers, but the two are regarded as distinct species.

Vema levinae Warén, sp. n. is described from a submarine volcano off western Mexico. The type species of Rokopella and Veleropilina are redescribed, the usage of the names is discussed and Rokopella and Veleropilina are recognized as valid genera in Neopilinidae. Rokopella euglypta(Dautzenberg & Fischer, 1897) is redescribed from shells and a single live specimen taken from seamounts south of the Azores, from a depth of 1200–1600 m. Tectura reticulata Seguenza, 1876 (Gastropoda, ‘Acmaeidae’, southern Italy, Upper Pliocene/Lower Pleistocene) is considered to have been based on the monoplacophoran species previously known as Neopilina zografi from the Mediterranean, and is classified in the genus Veleropilina. Veleropilina zografi (Dautzenberg & Fischer, 1896) is redescribed based on shells from several seamounts south of the Azores. It is considered distinct from Rokopella euglypta and classified in the genus Veleropilina. An undescribed species of Veleropilina from a seamount off southern Baja California is reported, figured and discussed but not formally described.

Zerotulidae fam. nov. is described and placed in the Littorinoidea. The family includes the genera Zerotula Finlay, 1926 (formerly in Architectonicidae); Frovina Thiele, 1912 (synonymized with Prolacuna Thiele, 1913, both formerly in Naticidae); Trilirata Waren & Hain, gen. nov. (type species Prolacuna trilirata Thiele, 1912, Antarctic); and Dickdellia Waren & Hain, gen. nov. (type species Laevilitorina (Corneolitorina) labioflecta Dell, 1991, Antarctic, bathyal).The following new species are described: Frovina angularis Waren & Hain (New Caledonia, bathyal), Zerotula incognita Waren & Hain (North Atlantic, abyssal), Z. stellapolaris Waren & Hain (Antarctic), Z. coronata Waren & Hain (New Zealand, shelf), Trilirata sexcarinata Waren & Hain (Antarctic), T. triregis Waren & Hain (New Zealand, shelf), and T. herosae Waren & Hain (New Caledonia, bathyal). The anatomy is described for Frovina soror Thiele, 1912, F. indecora (Thiele, 1912), Zerotula stellapolaris, Trilirata macmurdensis (Hedley, 1911), T. sexcarinata, and D. labioflecta.Antitrichotropis wandelensis (Lamy, 1906,) (formerly in Capulidae, Neotaenioglossa) is transferred to Laevilitorininae (Littorinidae), based on examination of radula and external morphology of the head-foot. It is classified in Laevilitorina, subgenus Pellilacunella.

For the first time it has become possible to study a 'living fossil' Laevipilina antarctica, a representative of the family Neopilinidae (Mollusca, Monoplacophora) by means of transmission electron microscopy. This led to the discovery of a bacterial symbiosis in the epidermis of the mantle roof and of the head of the animal. Bacteria with varying morphologies were found between the microvilli of the epidermal cells. In addition, modified and specialized epidermal cells (bacteriocytes) were detected in the mantle roof and the post-oral tentacles. In contrast, the sole of the foot and the alimentary tract of the animal are free of symbionts. The bacterial symbionts may be involved in the recycling of dissolved organic matter.

Hypermastus mareticola is described from Guam, H. orstomi from New Caledonia, both parasitizing the heart urchin Maretia planulata. Hypermastus obliquistomum Waren, 1991 is recorded from the sand dollar Laganum depressum from New Caledonia (host species not recorded previously). Eulima encopicola is described from the Galapagos Islands, parasitizing the sand dollar Encope micropora galapagensis. Balcis clypeastericola Habe, 1976, parasitic on the clypeasteroid sea urchin Clypeaster japonicus in Japan, is made the type species of a new genus, Clypeastericola and a new species C natalensis lives on Clypeaster eurychoreus, from southeastern Africa. Two further records of species of Clypeastericola are recorded from Clypeaster australasiae (Gray), from New South Wales, and from Laganum depressum from New Caledonia, but the species are left undescribed.

Two new species of the genus Asterophila Randall and Heath, 1912 (Prosobranchia, Eulimidae) are described, A. perknasteri from the Antarctic starfish Perknaster sp. (Valvatida, Ganeriidae) and A. rathbunasteri from the californian starfish Rathbunaster californicus Fischer, 1906 (Forcipulatida, Asteriidae). A third species of Asterophila is reported from Freyella sp. (Brisingida, Brisingidae), from the southern part of the Kermadec Trench, but is not described.

The external morphology of the soft parts, the shell, and the radula are described for the two Mediterranean gastropod species Oxystele depressa Granata (formerly in the Skeneidae) and Skenea pellucida Monterosato (formerly in the Skeneopsidae). Oxystele depressa is transferred to Tomura Pilsbry & McGinty, 1946 (Cornirostridae). Skenea pellucida is made the type of Xenoskenea Waren & Gofas, gen. nov., and classified in the family Hyalogryinidae, a heterobranch family with rhipidoglossate radula. Noerrevangia fragilis Waren & Schander, gen. et sp. nov. (Cornirostridae) is described from shallow water around the Faeroe Islands.