Absence of resolution in phylogenetic trees, or metaphyly, is a common phenomenon. It mainly results from the fact that each data set has its own limit and can hardly be expected to reconstruct alone an entire hierarchy. Because metaphyly helps point out which regions of a tree merit further investigation, one should not avoid metaphyly but rather should try to detect it by addressing carefully node reliability. In this paper we explore the implication of Inetaphyly for species names. We present a phylogenetic analysis of Discodorididae (Mollusca, Gastropoda, Nudibranchia, Doridina), with an emphasis on relationships among species of Discodoris and its traditionally close 'allies' such as Peltodoris and Anisodoris. We demonstrate that some species must be transferred to different discodoridid subclades with which they share synapomorphies, but that many species form a metaphyletic group At the base of Discodorididae, and therefore cannot be placed in any taxon of genus level. We demonstrate that the current International Code of Zoological Nomenclature does not allow taxonomists to handle this situation because it requires selecting a taxon name of genus rank for every species binomial. Then we evaluate the results provided by new forms of species names, both in a rank-based system, such as the current nomenclature, and a rank-free system. All solutions considered would cause radical changes to the 'spirit' of the current ICZN (and, by extension, to the other current codes). In a rank-free system of nomenclature, such as the PhyloCode, the best result is obtained with an epithet-based form that does not mention supra-specific relationships. Under this method, official species names would take the form 'boboliensis Bergh, 1877', although page numbers and letters can be added for uniqueness purposes. Taxonomists would then be free to add supra-specific taxon names in 'common' species names, such as Discodorididae boholiensis Bergh, 1877 or simply Discodorididae boboliensis. Here we wish to stimulate discussion of a problem that we believe merits wide debate: absence of resolution in phylogenetic reconstruction and its impact on species nomenclature.

HALIPRO 1, MONTROUZIER

Recent morphological and molecular results on phylogeny of euthyneuran gastropods, which include opisthobranchs and pulmonates, have greatly diminished previous supposed resolution of their phylogenetic relationships. In addition to recent morphological results, sequences of the D1 and D2 domains of the 28S rRNA are here analyzed by parsimony for 31 euthyneuran species. The molecular and previous morphological data sets were not congruent according to an ILD test, and morphological and molecular data could not be analyzed simultaneously. Consequently Bremer’s Combinable Component Consensus was used to obtain a new tree, with the following supported molecular results: monophyly of a new clade of opisthobranchs including actively swimming Euthyneura, i.e., pelagic Gymnosomata and Thecosomata plus benthic Anaspidea; first molecular confirmation of monophylies of Hygrophila, including Chilina, Acteonoidea, and Sacoglossa, which include both shellbearing species and slugs; and new confirmation of the monophyly of Stylommatophora. Morphological characters which support the new clades obtained here are discussed.

BATHUS 2, Restreint, MUSORSTOM 9

Pleurobranchaeidae from deep sea collections made off the Philippines, Indonesia, Coral Sea, Vanuatu, and the Marquesas Islands, are investigated. Pleurobranchaea catherinae sp. novo is described from depths between 346 and 820 m and represents the first deep-sea species of Pleurobranchaea from the Indo-Pacific. Pleurobranchella nicobarica Thiele, 1925 is newly recorded from Vanuatu, Philippines and the Marquesas, and its anatomy is described. Gigantonotum Lin & Tchang, 1965 is confirmed as a synonym of Pleurobranchella.

KARUBAR, MUSORSTOM 1, MUSORSTOM 2, MUSORSTOM 3, MUSORSTOM 5, MUSORSTOM 8, MUSORSTOM 9

Basal discodorids, with an emphasis on Discodoris and Peltodoris, are revised for the first time. Hundreds od specimens were examined, including all type availables. The individuals variation of morphological characters is evaluated and taken into account for species delineation. Discodorids species are rediscribed based on large numbers of individuals: e.g., 98 individuals were dissected for Sebadoris fragilis (Alder and Hancock, 1864). The nomenclature status (valid name, synonym, nomen dubium) of 125 species names is adressed. Prior to the present study, there were 106 valid names, 13 synonyms, two nomina dubia, three permanently invalid names, one nomen nudum; after revision, there are 39 valid names, 12 synonyms (out of the 13 former synonyms), 25 new synonyms, 27 nomina dubia, three permanently invalid names, one nomen nudum, and 18 names that refer to poorly-know species (which could be nomina dubia, synonyms or valid names). Those numbers confirm again the critical need for taxonomic revisions in order to obtain a reliable knowledge on species biodiversity. Also, the high proportion of new synontyms and new nomina dubia is related to the fact that many discodorids were described based on few specimens (of the 81 Discodoris species names, only five were originally created with more than 4 specimens). Another important factor that explains the high proportion of new synonyms and nomina dubia is the large number of incomplete originale descriptions. The supra-specific relationships of all species considered are addressed based on cladistic analysis. Discodoris is a clade including only two of all the former Discodoris species: Discodoris boholiensis Bergh, 1877, the type species of Discodoris under the ICZN, and Discodoris cebuensis Bergh, 1877. Peltodoris is a clade including only three species: Peltodoris atromaculata Bergh, 1880, the type speces of Peltodoris under the ICZN, Peltodoris mullineri Millen and Bertsch, 2000, and Peltodoris murrea (Abraham, 1877). Also, several species are re-allocated to different discodorid clades: e.g., Discodoris fragilis (Alder and Hancock, 1864) transferred to Sebadoris, Doris raripilosa Abraham, 1877 to Asteronotus, and Discodoris crawfordi Burn, 1969 to Rostanga. However, 50 species (including 21 valid species, 17 nomina dubia, and 12 poorly know species) could not be places in any of the discodorid clades (genera), and therefore are part of a metaphyletic group at the base of Discodorididae. There are 50 species names for which we cannot use a generic name as the first part of the Linnaean binomial. This situation is handled in two ways. First, "Montereina", is used as a genus name for all the species that are part of the metaphyletic group at the base of Discodorididae (the quotation marks indicate that this genus name does not refer to a clade), which is compatible with the ICZN but contradicts phylogenetic principles. Second, the clade name Discodorididae is used as a clade address for those species that cannot be placed in a clade of "generic" rank, which is compatible with the International Code of Phylogenetic Nomenclature (ICPN), or PhyloCode. The use of a supra-generic name instead of a generic name in front of a specific name is implemented in a monographic revision for the first time here, and represents a major change in our nomenclature practices. The vast majority of the species regarded as valid here are efficently delineated based on morphological features (mainly the dorsal color, the shape of the radular teeth, and the reproductive system). However, in a few cases, such as in Tayuva, it seems that species cannot be distinguished morphologically. Future possible studies that could help solve those taxonomic issues are discussed. Seven new species are describes. However, those new species are not formally named for a variety of reasons (mainly because not enough information was available). Finally, many new records are provided, especially from the tropical Indo-West Pacific.

BATHUS 3, BIOCAL, LIFOU 2000, MONTROUZIER, MUSORSTOM 4, MUSORSTOM 8

In the context of a complete revision of the Onchidiidae, it is shown here that Onchidium vaigiense Quoy & Gaimard, 1825 and Onchidium marmoratum Lesson, 1831 belong to a clade that is separate from all other onchidiid genera and so a new genus is described: Marmaronchis Dayrat & Goulding, new genus. Marmaronchis slugs are characterised by a unique combination of anatomical traits: intestinal loops of type I, rectal gland present, accessory penial gland present. Marmaronchis vaigiensis and M. marmoratus are cryptic externally and internally but are delineated as distinct species with both mitochondrial (COI, 16S, 12S) and nuclear (ITS2, 28S, H3) DNA sequences. Onchidium ambiguum Semper, 1880 and O. steenstrupii Semper, 1882 are proposed as new junior synonyms of M. vaigiensis. Marmaronchis slugs primarily live in the rocky intertidal and, unlike many onchidiids from Southeast Asia, they are not found inside mangroves. Both Marmaronchis species are geographically sympatric and can even be found at the same stations, but Marmaronchis vaigiensis is widely distributed, from the Nicobar Islands (Bay of Bengal) all the way to Vanuatu and the Philippines, while M. marmoratus is only known from New Ireland and Madang (Papua New Guinea). Several new geographical records are provided: Bali and Sulawesi (Indonesia) and Vanuatu for M. vaigiensis; Madang (Papua New Guinea) for M. marmoratus. The diversity of Marmaronchis slugs is compared to other onchidiid genera.

PAPUA NIUGINI, SANTO 2006

In the context of a complete revision of the Onchidiidae, it is shown here that Onchidium vaigiense Quoy & Gaimard, 1825 and Onchidium marmoratum Lesson, 1831 belong to a clade that is separate from all other onchidiid genera and so a new genus is described: Marmaronchis Dayrat & Goulding, new genus. Marmaronchis slugs are characterised by a unique combination of anatomical traits: intestinal loops of type I, rectal gland present, accessory penial gland present. Marmaronchis vaigiensis and M. marmoratus are cryptic externally and internally but are delineated as distinct species with both mitochondrial (COI, 16S, 12S) and nuclear (ITS2, 28S, H3) DNA sequences. Onchidium ambiguum Semper, 1880 and O. steenstrupii Semper, 1882 are proposed as new junior synonyms of M. vaigiensis. Marmaronchis slugs primarily live in the rocky intertidal and, unlike many onchidiids from Southeast Asia, they are not found inside mangroves. Both Marmaronchis species are geographically sympatric and can even be found at the same stations, but Marmaronchis vaigiensis is widely distributed, from the Nicobar Islands (Bay of Bengal) all the way to Vanuatu and the Philippines, while M. marmoratus is only known from New Ireland and Madang (Papua New Guinea). Several new geographical records are provided: Bali and Sulawesi (Indonesia) and Vanuatu for M. vaigiensis; Madang (Papua New Guinea) for M. marmoratus. The diversity of Marmaronchis slugs is compared to other onchidiid genera.

KAVIENG 2014, PAPUA NIUGINI

Mangroves of the Indo-West Pacific have remained poorly explored, so even the diversity of the onchidiid slugs, which are some of the most abundant animals in mangroves of the Indo-West Pacific, is not well known. Thanks to several years spent exploring mangroves in the Indo-West Pacific (more than 260 stations), especially in South-East Asia, the diversity of mangrove gastropods can now be addressed through revisions following an integrative taxonomy approach (nomenclature, field observations, comparative anatomy and DNA sequences). A new genus of onchidiid slugs is described, Paromoionchis Dayrat & Goulding gen. nov., which includes five species, three of which are new: Paromoionchis boholensis Dayrat & Goulding gen. et sp. nov., P. daemelii (Semper, 1880) com. nov., P. goslineri Dayrat & Goulding gen. et sp. nov., P. penangensis Dayrat & Goulding gen. et sp. nov. and P. tumidus (Semper, 1880) comb. nov. Paromoionchis gen. nov. is distributed from western India to the subtropical waters of Japan (33° N) and southeastern Australia (33° S). The creation of new taxon names is supported by rigorous nomenclature: the types of all existing species names in the family were examined, the original descriptions carefully studied and nomenclatural issues addressed. The diversity and biogeography of this new genus is discussed in a broader context.

PAPUA NIUGINI

A new species, Onchidium melakense Dayrat & Goulding, sp. nov., is described, bringing the total to four known species in the genus Onchidium Buchannan, 1800. Onchidium melakense is a rare species with only nine individuals found at three mangrove sites in the Andaman Islands and the Strait of Malacca (western Peninsular Malaysia and eastern Sumatra). The new species is delineated based on mitochondrial (COI and 16S) and nuclear (ITS2 and 28S) DNA sequences as well as comparative anatomy. Each Onchidium species is characterized by a distinct color and can easily be identified in the field, even in the Strait of Malacca where there are three sympatric Onchidium species. An identification key is provided. In addition, Onchidium stuxbergi (Westerlund, 1883) is recorded for the first time from eastern Sumatra, and Onchidium pallidipes Tapparone-Canefri, 1889, of which the type material is described and illustrated here, is regarded as a new junior synonym of O. stuxbergi.

PAPUA NIUGINI

The genus Peronia Fleming, 1822 includes all the onchidiid slugs with dorsal gills. Its taxonomy is revised for the first time based on a large collection of fresh material from the entire Indo-West Pacific, from South Africa to Hawaii. Nine species are supported by mitochondrial (COI and 16S) and nuclear (ITS2 and 28S) sequences as well as comparative anatomy. All types available were examined and the nomenclatural status of each existing name in the genus is addressed. Of 31 Peronia species-group names available, 27 are regarded as invalid (twenty-one synonyms, sixteen of which are new, five nomina dubia , and one homonym), and four as valid: Peronia peronii (Cuvier, 1804), Peronia verruculata (Cuvier, 1830), Peronia platei (Hoffmann, 1928), and Peronia madagascariensis (Labbé, 1934a). Five new species names are created: P. griffithsi Dayrat & Goulding, sp. nov. , P. okinawensis Dayrat & Goulding, sp. nov. , P. setoensis Dayrat & Goulding, sp. nov. , P. sydneyensis Dayrat & Goulding, sp. nov. , and P. willani Dayrat & Goulding, sp. nov. Peronia species are cryptic externally but can be distinguished using internal characters, with the exception of P. platei and P. setoensis . The anatomy of most species is described in detail here for the first time. All the secondary literature is commented on and historical specimens from museum collections were also examined to better establish species distributions. The genus Peronia includes two species that are widespread across the Indo-West Pacific ( P. verruculata and P. peronii ) as well as endemic species: P. okinawensis and P. setoensis are endemic to Japan, and P. willani is endemic to Northern Territory, Australia. Many new geographical records are provided, as well as a key to the species using morphological traits.

KAVIENG 2014, PAPUA NIUGINI

Many marine species are specialized to specific parts of a habitat. In a mangrove forest, for instance, species may be restricted to the mud surface, the roots and trunks of mangrove trees, or rotting logs, which can be regarded as distinct microhabitats. Shifts to new microhabitats may be an important driver of sympatric speciation. However, the evolutionary history of these shifts is still poorly understood in most groups of marine organisms, because it requires a well-supported phylogeny with relatively complete taxon sampling. Onchidiid slugs are an ideal case study for the evolutionary history of habitat and microhabitat shifts because onchidiid species are specialized to different tidal zones and microhabitats in mangrove forests and rocky shores, and the taxonomy of the family in the Indo-West Pacific has been recently revised in a series of monographs. Here, DNA sequences for onchidiid species from the North and East Pacific, the Caribbean, and the Atlantic are used to reconstruct phylogenetic relationships among Onchidella species, and are combined with new data for Indo-West Pacific species to reconstruct a global phylogeny of the family. The phylogenetic relationships of onchidiid slugs are reconstructed based on three mitochondrial markers (COI, 12S, 16S) and three nuclear markers (28S, ITS2, H3) and nearly complete taxon sampling (all 13 genera and 62 of the 67 species). The highly-supported phylogeny presented here suggests that ancestral onchidiids most likely lived in the rocky intertidal, and that a lineage restricted to the tropical Indo-West Pacific colonized new habitats, including mudflats, mangrove forests, and high-elevation rainforests. Many onchidiid species in the Indo-West Pacific diverged during the Miocene, around the same time that a high diversity of mangrove plants appears in the fossil record, while divergence among Onchidella species occurred earlier, likely beginning in the Eocene. It is demonstrated that ecological specialization to microhabitats underlies the divergence between onchidiid genera, as well as the diversification through sym­ patric speciation in the genera Wallaconchis and Platevindex. The geographic distributions of onchidiid species also indicate that allopatric speciation played a key role in the diversification of several genera, especially Onchidella and Peronia. The evolutionary history of several morphological traits (penial gland, rectal gland, dorsal eyes, intestinal loops) is examined in relation to habitat and microhabitat evolutionary transitions and suggests that the rectal gland of onchidiids is an adaptation to high intertidal and terrestrial habitats.

PAPUA NIUGINI

The BORDAU 1 cruise was carried out in the Fijian Archipelago from 22 February to 14 March 1999 on board of R.V. "Alis". A total of 118 samples were made by dredging and trawling in the upper bathyal zone and in the circalittoral depths of the islands and on the seamounts in the Lau Ridge. The upper part of the slope to 600 m consists of hard bottoms and deeper muddy bottoms with pumice. In some islands particularly isolated (Vanua Balavu, Yacata, Aiwa and Yagasa), the landsnails were sampled.

BORDAU 1