Although raphitomid snails are a dominant component of gastropod communities in deep seas worldwide, their systematics is still largely tentative. We assembled the most complete sampling of Raphitomidae from south-eastern Australia to date. Based on morphological and molecular data from this material, we produced a robust phylogenetic framework and used it to delimit genera. For the focus area, our results show a large proportion of undescribed species- and genus-level taxa, 11 of which are formally described herein. We demonstrate that the examination of purely morphological characters rarely suffices for the purpose of accurate genus delimitation. As a result, some traditionally highly diverse raphitomid genera (such as Gymnobela) turn out to be artificial assemblages of several unrelated, mostly undescribed, genus-level lineages. Our data suggest that comparable configurations of shell and radular features, observed at the genus level, commonly do not reflect true phylogenetic relationships. However, our results are inconclusive as to whether homoplasy or conservatism are the drivers of this phenomenon. Accommodating for the inevitable sampling biases, south-eastern Australia appears as a possible hotspot for both raphitomid diversity and endemism, when compared with adjacent areas.

Background Our knowledge of the benthic fauna at lower bathyal to abyssal (LBA, > 2000 m) depths off Eastern Australia was very limited with only a few samples having been collected from these habitats over the last 150 years. In May–June 2017, the IN2017_V03 expedition of the RV Investigator sampled LBA benthic communities along the lower slope and abyss of Australia’s eastern margin from off mid-Tasmania (42°S) to the Coral Sea (23°S), with particular emphasis on describing and analysing patterns of biodiversity that occur within a newly declared network of offshore marine parks. Methods The study design was to deploy a 4 m (metal) beam trawl and Brenke sled to collect samples on soft sediment substrata at the target seafloor depths of 2500 and 4000 m at every 1.5 degrees of latitude along the western boundary of the Tasman Sea from 42° to 23°S, traversing seven Australian Marine Parks. Results The biological sampling included 35 beam trawls, 28 Brenke sleds, 8 box cores, 20 surface meso-zooplankton tows, and 7 Deep Towed Camera transects. In total, 25,710 specimens were identified to 1084 taxonomic entities, including 847 species-level, 144 genus-level and 69 family-level and 24 higher-level taxa. Of the species-level taxa, only 457 were assigned species-level taxonomic names, which implies that up to 58% of the collected fauna is undescribed. In addition, the ranges of numerous species have been extended to include the western Tasman Sea. Conclusions The lower bathyal and abyssal fauna of soft sediment seafloors off eastern Australia has been systematically surveyed for the first time. The resultant collections will provide the foundation for much future ecological, biogeographical, phylogenetic and taxonomic research.

The deep-sea malacofauna of temperate Australia remains comparatively poorly known. However, a recent influx of DNA-suitable material obtained from a series of deep-sea cruises has facilitated integrative taxonomic study on the Conoidea (Caenogastropoda:Neogastropoda). Building on a recent molecular phylogeny of the conoidean family Raphitomidae, this study focussed on the genera Gladiobela and Pagodibela (both Criscione, Hallan, Puillandre & Fedosov, 2020). We subjected a representative mtDNA cox1 dataset of deep-sea raphitomids to ABGD, which recognised 14 primary species hypotheses (PSHs), 9 of which were converted to secondary species hypotheses (SSHs). Following the additional examination of the shell and hypodermic radula features, as well as consideration of bathymetric and geographic data, seven of these SSHs were recognised as new to science and given full species rank. Subsequently, systematic descriptions are provided herein. Of these, five are attributed to Gladiobela (three of which are endemic to Australia and two more widely distributed) and two are placed in Pagodibela (one endemic to southern Australia and one widespread in the Pacific). The rarity of many ‘turrids’ reported in previous studies is confirmed herein, as particularly indicated by highly disjunct geographic records for two taxa. Additionally, several of the studied taxa exhibit wide Indo-Pacific distributions, suggesting that wide geographic ranges in deep-sea ‘turrids’ may be more common than previously assumed. Finally, impediments to deep-sea ‘turrid’ taxonomy in light of such comparative rarity and unexpectedly wide distributions are discussed.

The bivalve family Corbulidae, known colloquially as ‘basket clams’, includes species tolerating a wide variety of habitats ranging from open marine to freshwater. Previous studies of corbulid phylogenetics have been based mainly on shell morphology and to some extent soft tissue anatomy. However, these studies have been inadequate for corbulid classification because of difficulties in determining the inter‐relationships of primarily marine species with non‐marine species, the latter commonly exhibiting highly divergent morphological, ecological and environmental characteristics from their marine counterparts. The first molecular phylogenetic study of the Corbulidae is presented herein, analysing DNA sequences from the 18S rRNA and 28S rRNA genes, separately and in combination. Fifteen corbulid species and 14 outgroup taxa were included in the analyses. Corbulidae is resolved as monophyletic, comprising three groups with varying support. The non‐marine species form one group that we name as the subclade ‘limnetic–euryhaline Corbulidae’ (LEC) and comprising the genera Lentidium, Erodona and Potamocorbula. This LEC, which is consistently recovered as monophyletic, is globally distributed. The marine Corbulidae are divided into two well‐supported lineages in combined analyses although there are inconsistencies in their membership between single‐gene analyses. One of the two lineages consists of primarily Western Pacific taxa and the other of North American and Caribbean taxa. Finally, the authors advocate further study on the LEC to mitigate potential biological invasions beyond their native distribution.

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