Northern Papua New Research Articles

Waking the “sleeping giant?” Mid- to Late-Holocene environment and fire history in the Aitape area, northern Papua New Guinea

The coastlines of the southwestern Pacific are dynamic environments that have been repeatedly reshaped by tectonic forces as well as changing global climate and sea level. It has been theorized that much of the north coast of New Guinea was sparsely inhabited until stabilization of coastal flats fallowing the Mid-Holocene Thermal Maximum and resulting marine high stand. We report on environmental proxy indicators measured in core samples taken near modern day Aitape, Papua New Guinea. These cores record the formation of a large lagoonal system on the modern coastal flats by 5800 cal BP. This lagoon infilled over the next several 1000 years as sea level dropped, with the modern coastal flats stabilizing by 1400 cal BP. A charcoal record spanning the period between 6200 and 1400 cal BP documents substantial increases in influx between ~6200 and 6000 cal BP and particularly from ~3000 to 2600 cal BP. Comparison to regional charcoal and ENSO records suggests that increasing aridity and ENSO intensity may drive regional patterning in fire records, however, localized charcoal records are also heavily influenced by human activity. Between 3000 and 2600 cal BP, forest management practices in the Aitape area, currently focused on tree crops and horticulture characterized by long fallowing and limited burning, shifted to a regime characterized by large scale forest clearance and shorter fallowing. We hypothesize that increasing population driven by abundant Mid-Holocene lagoonal resources may have been difficult to maintain as lagoons infilled and climate became more variable, leading to horticultural intensification.

Two new species of green treefrogs (Pelodryadidae: Litoria) from the northern slopes of Papua New Guinea's Central Cordillera.

We describe two new species of moderate-sized (male body length 26.5-29.8 mm and 41.0 mm), predominantly green treefrogs in the genus Litoria from hill forest on the northern slopes of Papua New Guinea's Central Cordillera. Phylogenetic analysis of mitochondrial ND4 nucleotide sequences shows that the first species is related to Litoria iris (Tyler) and its allies. It is morphologically most similar to Litoria mystax, a small green treefrog known only from the holotype that was described more than 100 years ago from the north coast of western New Guinea but differs from that species in having longer legs and a broader head. The second species is closest to Litoria gasconi, a species known only from the foothills of the Foja Mountains in Papua Province, Indonesian New Guinea, and the Prince Alexander Mountains in northern Papua New Guinea. It has a net average sequence divergence of 10% from L. gasconi and can be distinguished morphologically from it and from other pelodryadids by the presence of a striking pattern of spots and blotches on the ventral surfaces and on the hidden surfaces of the limbs. These descriptions add to the rapidly increasing known diversity of frogs in hill and lower montane forest, habitats that support the most diverse frog communities on mainland New Guinea.

Phylogenetic placement, morphology and gill-associated bacteria of a new genus and species of deep-sea mussel (Mytilidae: Bathymodiolinae) from the South China Sea

Mussels in the subfamily Bathymodiolinae are common inhabitants of deep-sea chemosynthetic habitats, but in many places their diversity remains unknown. Here we describe Nypamodiolus samadiae n. gen. et n. sp. (Mytilidae: Bathymodiolinae) based on samples collected from the Haima cold seep in the South China Sea. Phylogenetic analyses based on fragments of three mitochondrial (cox1, 16S rRNA and nad4) and three nuclear (18S rRNA, 28S rRNA and histone H3) genes show that this new species belongs to a new genus, Nypamodiolus, which includes three named species (Myrina longissima Thiele and Jaeckel, 1931, Myrina simpsoni Marshall, 1900, Idasola japonica Habe, 1976) and a few undescribed species. Nypamodiolus n. gen. is characterized by small-sized, modioliform to fan-shaped shells with the umbones in a non-terminal position, and by robust anterior and posterior byssal retractor muscles arranged in roughly one plane. Most closely related to Nypamodiolus samadiae n. sp. is an undescribed species from the northern Papua New Guinea, to which it has a Kimura-2-parameter genetic distance of 11.8% for cox1. Sequencing the V3–V4 region of the microbial 16S rRNA gene reveals two dominant gill-associated bacteria in the new species, including one sulfur-oxidizing Gammaproteobacteria (relative abundance: 43.8–58.8%) and one unclassified Spirochaetes (relative abundance: 23.9–28.1%). Morphologically, N. samadiae n. sp. is similar to N. simpsoni, while can be distinguished by a larger maximum shell size (45.0 mm vs. 40.0 mm), larger length/height ratio (2.6–2.9 vs. 2.1–2.4), broader posterior end, slightly curved dorsal margin, and more anterior umbones.

Bycatch of a Critically Endangered Shark Glyphis glyphis in a Crab Pot Fishery: Implications for Management

The speartooth shark Glyphis glyphis is a Critically Endangered whaler shark known from a few tropical river systems in northern Australia and Papua New Guinea. There is limited genetic exchange in populations residing in northern Australian rivers that are greater than 100 km apart. In Queensland, the species is only found in the Wenlock and Ducie River that flow into Port Musgrave. Juveniles are confined to upstream reaches of these rivers with seasonal downstream movement related to freshwater influx. This region also supports commercial and recreational fisheries including crab pot and gillnet fisheries. Being obligate ram-ventilators, entrapment in crab pots results in mortality of bycaught speartooth sharks after a few hours. Following anecdotal reports of juvenile speartooth sharks being captured in crab pots, we investigated catch rates in crab pots experimentally and examined commercial fishing effort in the Wenlock and Ducie River from logbook data. Twenty four juvenile (55–80 cm TL) speartooth sharks were captured in experimental crab pots in the Ducie River and Tentpole Creek (a tributary of the Wenlock River) with catch rates high; up to 0.82 (±1.86 SD) sharks pot–1 day–1. Experimental catch rates in crab pots varied between rivers and with distance upstream and were highest in areas of highest shark density based on detection of acoustically tagged sharks over 7 years and line fishing catch per unit effort data. Although commercial crab effort varies spatially and temporally in relation to current catch rates and market demands, consistent monthly overlap with juvenile speartooth shark core distribution occurred throughout the year. Using CPUE data multiplied by fishing effort in Tentpole Creek, we estimate that in November alone, between 51 and 279 speartooth sharks are potentially captured in years with high fishing effort. Bycatch of juvenile speartooth sharks in commercial and recreational crab pots poses a significant threat to this genetically isolated and small population. Urgent management intervention to drastically reduce bycatch mortality either through gear modifications or spatial closures are required to ensure the viability of this population.

(Meta)Physical Homelessness In Behrouz Boochani’s No Friend But The Mountains

Abstract Behrouz Boochani is a Kurdish-Iranian writer who was detained on Manus Island, in northern Papua New Guinea, for more than four years. During these years of detention, he wrote a book in WhatsApp messages on his phone: No Friend but the Mountains (2018). Although understandably sold as non-fiction and therefore marketed mostly as a testimony, Boochani’s interweaving of different genres renders the book resistant to classification, just as its author is difficult to define and ‘categorize’ in our world of nation states and borders. This article explores an important nucleus of Boochani’s book, a motif that runs through his narrative, both explicitly and figuratively: home and homelessness. I argue that the loss of home is normatively and performatively repeated in Manus Prison, presenting the prisoners with a form of discipline and violence both physical and metaphysical. After losing the right to their place, the detainees gradually lose their ability to conceive of a different world that includes the homeless.

Nine new species of Enithares (Heteroptera: Notonectidae) from New Guinea, with distributional notes on other species and an updated world checklist.

Nine new species of Enithares are described from New Guinea and immediately adjacent islands: E. peninsularis from the Owen Stanley Mountains of the Papuan Peninsula, E. bosavi and E. papua from southern Papua New Guinea, E. orsaki from northern Papua New Guinea, E. insularis from the D'Entrecasteaux Islands, E. tagula from the Louisiade Archipelago, E. ziwa from the central mountains of western New Guinea, E. arfak from the Arfak Mountains of the eastern Vogelkop Peninsula, and E. kasim from the western Vogelkop Peninsula. Enithares bakeri is newly recorded from New Guinea, and in combination with the new species described above brings the total number of species of Enithares in New Guinea to 16, and the regional total to 19 when including nearby islands of Waigeo, Biak, the D'Entrecasteaux group, and the Louisiade Archipelago. The species concept of E. atra is clarified and geographically restricted to southeastern New Guinea; specimens previously recorded under this name from northern New Guinea are shown to represent the new species E. orsaki. Additional distribution records for 15 previously described Enithares species are provided for many localities in the Malay Archipelago and mainland Southeast Asia, including the first records of E. bakeri from Lombok, Flores, Timor, Halmahera, and Obi; the first record of E. paramegalops from Ambon; the first records of E. gibbera from Kolombangara and Malaita in the Solomon Islands; the first record of E. intricata from Bali; the first records of E. lombokensis from Flores and Sumba; the first records of E. ripleyana from Halmahera, Ternate and Tidore; and the first record of E. ciliata from Borneo. Photomicrographs of key characters and distribution maps are provided for all new species described, accompanied by an updated world checklist for the genus with distributional notes and associated references.

Fishers’ ecological knowledge of sawfishes in the Sepik and Ramu rivers, northern Papua New Guinea

Fishers’ ecological knowledge of sawfishes in the Sepik and Ramu rivers, northern Papua New Guinea

Redescription of Chimaera ogilbyi (Chimaeriformes; Chimaeridae) from the Indo-Australian region.

An integrated taxonomic approach, combining both morphological and molecular data, was adopted to investigate the Hydrolagus lemures-ogilbyi group in the Indo-Australian region. Single mitochondrial markers (CO1 and NADH2) provided evidence supporting the separation of four distinct species in this group. However, detailed morphological data collected from specimens from across their range failed to find any consistent differences, and many features previously considered to be diagnostic were found to be variable. Nuclear DNA data also failed to support the differences found with the single mitochondrial markers and, together with the morphological data, supported the hypothesis that only a single species in this group is present in the Indo-Australian region. In addition, the results failed to support the current generic placement of this group in Hydrolagus, suggesting they belong to the genus Chimaera with doubt over the validity of Hydrolagus as a valid genus. The oldest available name for this group is Chimaera ogilbyi and a redescription is provided. This species occurs throughout Australia, eastern Indonesia (Java, Bali, and Lombok) and northern Papua New Guinea.

Reassessing the environmental context of the Aitape Skull - The oldest tsunami victim in the world?

There is increasing recognition of the long-lasting effects of tsunamis on human populations. This is particularly notable along tectonically active coastlines with repeated inundations occurring over thousands of years. Given the often high death tolls reported from historical events though it is remarkable that so few human skeletal remains have been found in the numerous palaeotsunami deposits studied to date. The 1929 discovery of the Aitape Skull in northern Papua New Guinea and its inferred late Pleistocene age played an important role in discussions about the origins of humans in Australasia for over 25 years until it was more reliably radiocarbon dated to around 6000 years old. However, no similar attention has been given to reassessing the deposit in which it was found—a coastal mangrove swamp inundated by water from a shallow sea. With the benefit of knowledge gained from studies of the 1998 tsunami in the same area, we conclude that the skull was laid down in a tsunami deposit and as such may represent the oldest known tsunami victim in the world. These findings raise the question of whether other coastal archaeological sites with human skeletal remains would benefit from a re-assessment of their geological context.

The talitrid amphipod genus Talorchestia from the South China Sea to the Indonesian Archipelago (Crustacea, Senticaudata)

We redescribe Talorchestia gracilis (Dana, 1852a) for the first time and designate a neotype based on new collections from Pulau Layang-Layang, Swallow Reef, South China Sea. We describe T. bunaken sp. nov. from Bunaken Island, Northern Sulawesi, Indonesia, T. dili sp. nov. from Dili, Timor-Leste, T. seringat sp. nov. from Singapore, T. sipadan sp. nov. from Sipadan Island, Sabah, Malaysia and T. yoyoae sp. nov. from Lombok, Indonesia. We report T. spinipalma (Dana, 1852a) from Madang, northern Papua New Guinea.

Tsunamis from submarine landslides

Most tsunamis are generated by earthquakes, with secondary, less frequent, mechanisms including subaerial and submarine landslides, volcanic eruptions and (extra‐terrestrial) bolide impacts. Different mechanisms generate tsunamis with different magnitudes, travel distances and impacts. Submarine landslides had been mapped and studied for decades but records suggested that only a few had generated tsunamis, and that these were minor. It was not until 1998, when a slump on the seabed offshore of northern Papua New Guinea caused a tsunami wave up to 15 m high that killed over 2200 people, was the significance of submarine landslides in tsunami generation realised. A combination of new (multibeam) seabed mapping technology and the development of improved numerical tsunami models for tsunami generation led to the recognition of the landslide tsunami mechanism of the PNG event. As a result the hazard from submarine landslides in tsunami generation is now recognized and better understood. Extensive mapping of ocean margins reveals that submarine landslides are common. Although many of these probably generated tsunamis, few have been identified, so their hazard remains uncertain. This article describes how the hazard from submarine landslide tsunamis was first recognized, how submarine landslides generate tsunamis, why they were previously discounted as a major hazard, and their potential hazards. An important aspect of the recognition of the tsunami hazard from submarine landslides has been the significance of geology, which has contributed to a subject previously dominated by seismologists.

Etmopterus samadiae n. sp., a new lanternshark (Squaliformes: Etmopteridae) from Papua New Guinea.

A new species of lanternshark, Etmopterus samadiae (Squaliformes: Etmopteridae), is described from off northern Papua New Guinea, in the western Central Pacific Ocean. The new species resembles other members of the "Etmopterus lucifer" clade in having linear rows of dermal denticles and most closely resembles E. brachyurus from the western North Pacific. The new species occurs along insular slopes between 340 and 785 m depth. The new species can be distinguished from other members of the E. lucifer clade by a combination of characteristics, including length of anterior flank branch markings being slightly shorter than its posterior branch, a longer caudal base marking, and irregular and variable number of black, horizontal, dash-like marks on sides of body. Molecular analysis based on the NADH2 marker further supports the distinction of E. samadiae from other members of the E. lucifer clade.

Sustainability of wood-use in remote forest-dependent communities of Papua New Guinea

The impact of wood use by isolated Forest Dependent Communities (FDC) on forest conservation is not well understood. We present a study of wood use in the YUS area (combined watersheds of Yopno, Uruwa and Som rivers) in northern Papua New Guinea, where 57 communities depend on forests for their subsistence. Using a survey methodology based on the Poverty and Environment Network (PEN) survey protocol, we assess the annual volume of wood used, primary sources for this wood and evaluate the capacity of natural forest to sustainably support current rates of wood-use as well as their per capita CO2 emissions. The primary reason for wood extraction was for fuelwood (6.4kgperson−1day−1 or ∼11.1tonnehousehold−1year−1) and housing construction (0.6m−3household−1year−1). Fuelwood was collected primarily from areas close to the village, in fallow (grassland) and agroforestry land types, while construction wood was being sourced primarily from secondary and primary forests.The volume of construction wood currently harvested across YUS was approximately 11% the annual increase in timber volumes in available and accessible natural forest. Under this wood use rate and projected population growth (2.5–4%) these communities can harvest construction wood at a sustainable rate for between 55 and 90 years. Nonetheless, we demonstrate that the CO2 emissions from wood extraction, and in particular fuelwood, are high; approaching 1.15 tonnes CO2person−1year−1. Household surveys revealed that all smallholders had a strong interest in planting trees for production of wood for house construction, which could reduce pressures on forests and compensate for CO2 emissions.

The Collection of Snakes Made by Benoît Mys and Jan Swerts in Northern Papua New Guinea in 1982–85

Abstract. We studied for the first time a collection of 377 snakes assembled by Benoit Mys and Jan Swerts in Papua New Guinea (PNG) during 1982–85. The collection, stored at the Royal Belgian Institute of Natural Sciences (RBINS), contains specimens collected in rapid assessments of 45 mainland and island localities in Madang, East Sepik, West Sepik, and Morobe Provinces, and 8 localities from West New Britain and Manus Provinces. Thirty-three species from six families (Acrochordidae, Boidae, Colubridae, Elapidae, Pythonidae, Typhlopidae) were present in the collection, and we report a number of new morphological observations from unidentified Dendrelaphis, Tropidonophis, and Aspidomorphus, as well as from Stegonotus cf. parvus. We report 31 new island records for snakes. Combined with island distributional information extracted from literature and museum collections, we provide an updated overview of snake species occurrences on the islands off the north coast of PNG. The substantial contribution of a 30...

Urogymnus acanthobothrium sp. nov., a new euryhaline whipray (Myliobatiformes: Dasyatidae) from Australia and Papua New Guinea.

The Mumburarr Whipray, Urogymnus acanthobothrium sp. nov. is described from a single specimen taken from the Cambridge Gulf, Western Australia, and from images of 10 other specimens from northern Australia and Papua New Guinea (all observed but not collected). It is a very large ray that attains at least 161 cm disc width, making it amongst the largest of the whiprays. The ventral tail below the caudal sting has a low, short-based fold. A ventral tail fold (or a dorsal fold) has not been recorded for any other himanturin stingray in the Indo-West Pacific. Molecular data suggest it is most closely related to a similar but more widely distributed cognate, U. granulatus. Both of these species share a suboval disc shape, similar squamation patterns, and the tail posterior to the sting is entirely white (at least in small individuals). U. acanthobothrium sp. nov. differs from U. granulatus in having a longer and more angular snout, longer tail, more posteriorly inserted caudal sting, lacks white flecks on the dorsal surface, and the ventral disc is uniformly white (rather than white with a broad black margin). It co-occurs with two other morphologically distinct Urogymnus in the region (U. asperrimus and U. dalyensis). Like U. dalyensis it occurs in both brackish and marine waters. A key is proved to the members of the genus Urogymnus.

Submarine Landslides and Their Tsunami Hazard

Most tsunamis are generated by earthquakes, but in 1998, a seabed slump offshore of northern Papua New Guinea (PNG) generated a tsunami up to 15 m high that killed more than 2,200 people. The event changed our understanding of tsunami mechanisms and was the forerunner to two decades of major tsunamis that included those in Turkey, the Indian Ocean, Japan, and Sulawesi and Anak Krakatau in Indonesia. PNG provided a context to better understand these tsunamis as well as older submarine landslide events, such as Storegga (8150 BP); Alika 2 in Hawaii (120,000 BP), and Grand Banks, Canada (1929), together with those from dual earthquake/landslide mechanisms, such as Messina (1908), Puerto Rico (1928), and Japan (2011). PNG proved that submarine landslides generate devastating tsunamis from failure mechanisms that can be very different, whether singly or in combination with earthquakes. It demonstrated the critical importance of seabed mapping to identify these mechanisms as well as stimulated the development of new numerical tsunami modeling methodologies. In combination with other recent tsunamis, PNG demonstrated the critical importance of these events in advancing our understanding of tsunami hazard and risk. This review recounts how, since 1998, understanding of the tsunami hazard from submarine landslides has progressed far beyond anything considered possible at that time. ▪ For submarine landslide tsunamis, advances in understanding take place incrementally, usually in response to major, sometimes catastrophic, events. ▪ The Papua New Guinea tsunami in 1998, when more than 2,200 people perished, was a turning point in first recognizing the significant tsunami hazard from submarine landslides. ▪ Over the past 2 to 3 years advances have also been made mainly because of improvements in numerical modeling based on older tsunamis such as Grand Banks in 1929, Messina in 1908, and Storegga at 8150 BP. ▪ Two recent tsunamis in late 2018, in Sulawesi and Anak Krakatau, Indonesia, where several hundred people died, were from very unusual landslide mechanisms—dual (strike-slip and landslide) and volcanic collapse—and provide new motivations for understanding these tsunami mechanisms. ▪ This is a timely, state of the art review of landslide tsunamis based on recent well-studied events and new research on older ones, which provide an important context for the recent tsunamis in Indonesia in 2018.

First report of the Hawaiian genus Newhousia (Dictyotales, Phaeophyceae) from Madang, Papua New Guinea and description of the new species N. yhaga sp. nov.

Abstract The calcified encrusting brown-algal genus Newhousia was collected in 2012 from two sites in Madang Lagoon, northern Papua New Guinea. This is the first report of that enigmatic genus since its original description in 2004 from Oahu in the Hawaiian Islands. Morphologies of thalli from both Papuan localities agree with the original diagnosis and the published figures of the Hawaiian Newhousia imbricata. Ribulose-1,5-biphosphate carboxylase large subunit (rbcL) sequences of Papuan specimens were 96% identical to those of N. imbricata, and although there were no outstanding morphological differences between the Hawaiian and the Papuan specimens, the genetic divergence between the two strongly indicates they are not conspecific. A formal description of the new species, Newhousia yhaga, is provided and the phylogenetic implications of concatenated cox3, psbA and rbcL sequences evaluated. A multi-marker phylogeny was generated in the hope to establish the precise phylogenetic position of Newhousia within the order Dictyotales. Even though both Bayesian inference (BI) and maximum likelihood (ML) analysis point to Newhousia being sister to Lobophora, these results are not supported by ML bootstrap values. The present documentation of Newhousia in a southwest Pacific locality considerably extends the geographical range of this unusual genus.

Assessment of population genetic structure in the arbovirus vector midge, Culicoides brevitarsis (Diptera: Ceratopogonidae), using multi-locus DNA microsatellites.

Bluetongue virus (BTV) is a major pathogen of ruminants that is transmitted by biting midges (Culicoides spp.). Australian BTV serotypes have origins in Asia and are distributed across the continent into two distinct episystems, one in the north and another in the east. Culicoides brevitarsis is the major vector of BTV in Australia and is distributed across the entire geographic range of the virus. Here, we describe the isolation and use of DNA microsatellites and gauge their ability to determine population genetic connectivity of C. brevitarsis within Australia and with countries to the north. Eleven DNA microsatellite markers were isolated using a novel genomic enrichment method and identified as useful for genetic analyses of sampled populations in Australia, northern Papua New Guinea (PNG) and Timor-Leste. Significant (P < 0.05) population genetic subdivision was observed between all paired regions, though the highest levels of genetic sub-division involved pair-wise tests with PNG (PNG vs. Australia (FST = 0.120) and PNG vs. Timor-Leste (FST = 0.095)). Analysis of multi-locus allelic distributions using STRUCTURE identified a most probable two-cluster population model, which separated PNG specimens from a cluster containing specimens from Timor-Leste and Australia. The source of incursions of this species in Australia is more likely to be Timor-Leste than PNG. Future incursions of BTV positive C. brevitarsis into Australia may be genetically identified to their source populations using these microsatellite loci. The vector’s panmictic genetic structure within Australia cannot explain the differential geographic distribution of BTV serotypes.Electronic supplementary materialThe online version of this article (doi:10.1186/s13567-015-0250-8) contains supplementary material, which is available to authorized users.

Four new species of Mesomyzostoma (Myzostomida: Annelida)

ABSTRACTMesomyzostoma Remscheid, 1918 currently includes three described species that live in the coelom and/or gonads of comatulid crinoids: Mesomyzostoma reichenspergeri Remscheid, 1918, Mesomyzostoma katoi Okada, 1933 and Mesomyzostoma lanterbecqae Summers and Rouse, 2014 in Summers, Al-Hakim et al. 2014. Here we describe four new species of Mesomyzostoma and assess their phylogenetic relationships using 18S rRNA, cytochrome oxidase subunit I and 16S rRNA sequence data. We also designate a neotype for M. katoi as the original types appear to be lost. We record M. reichenspergeri from the Australian Great Barrier Reef and from northern Papua New Guinea, but samples from the type locality (Aru Islands, Indonesia) and previously recorded host are needed for confirmation. The new species of Mesomyzostoma are one Japanese species: Mesomyzostoma okadai sp. nov., and three Australian species: Mesomyzostoma lobus sp. nov., Mesomyzostoma leukos sp. nov. and Mesomyzostoma botulus sp. nov. The first infects the coelom of crinoid arms and pinnules, and the other three are found in crinoid oral discs. We also record M. leukos sp. nov. and M. botulus sp. nov. from Papua New Guinea. Phylogenetic analyses suggest that M. okadai sp. nov. is the sister group to all other Mesomyzostoma.

A new genus of Stenetriidae Hansen, 1905 (Asellota: Isopoda: Crustacea)from the Great Barrier Reef, Australia and the southwestern Pacific.

Onychatrium gen. nov. is described, with five included species: Onychatrium forceps sp. nov., the type species and Onychatrium torosus sp. nov., both from the Great Barrier Reef; Onychatrium entale (Nordenstam, 1946) comb. nov., from Tapateuen (= Tabiteue Island), Gilbert Islands; Onychatrium thomasi (Bolstad & Kensley, 1999) comb. nov., from Madang, Papua New Guinea; and Onychatrium echiurum (Nobili, 1906) comb. nov., and species inquirenda from the Tumaotu Islands, Eastern French Polynesia. The primary distinguishing characters for Onychatrium gen. nov. are a trapezoid pseudosrostrum, the male pereopod 1 with elongate dactylus (4.7-7.3 as long as proximal width), propodus with strongly produced and acute lobe, carpus with a distally acute, flat, ventrally directed process (except O. torosus sp. nov., which has a short and truncate process) and the merus with a distally directed inferodistal lobe. The genus is known only from the southern Pacific, from the Tuamotus (eastern French Polynesia) to the Great Barrier Reef and northern Papua New Guinea.