Geochemistry of rare earth elements in cobalt-rich crusts from the Mid-Pacific M seamount

Rare earth elements（REEs） and major elements of 25 cobalt-rich crusts obtained from different depths of Mid-Pacific M seamount were analyzed using inductively coupled plasma-atomic emission spectrometer and gravimetric method.The results showed that they were hydrogenous crusts with average ∑REE content of 2084.69 μg/g and the light REE（LREE）/heavy REE（HREE） ratio of 4.84.The shale-normalized REE patterns showed positive Ce anomalies.The total content of strictly trivalent REEs increased with water depth.The Ce content and LREE/HREE ratios in Fe-Mn crusts above 2000 m were lower than those below 2000 m.The change in REE with water depth could be explained by two processes：adsorptive scavenging by setting matters and behaviors of REE in seawater.However, the Ce abundance took no obvious correlation with water depth reflects the constant Ce flux.The Ce in crusts existed mainly as Ce（IV）, implying that the oxidative-enriching process was controlled by kinetic factors.

The distribution of iodine and effects of phosphatization on it in the ferromanganese crusts from the Mid-Pacific Ocean

In the present paper, iodine （I）, iron （Fe）, manganese （Mn）, cobalt （Co）, phosphorus （P） and calcium （Ca） contents in three ferromanganese crusts from the Pacific Ocean are measured by spectrophotometric method and inductively coupled plasma atomic emission spectrometers （ICP-AES） to investigate the contents and distribution of iodine in ferromanganese crusts. The results show that iodine contents in three crusts vary between 27.1 and 836 mg/kg, with an average of 172 mg/kg, and the profile of iodine in the three crusts all exhibits a two-stage distribution zone： a young non-phosphatized zone and an old phosphatized zone that is rich in I, P and Ca. The iodine content ratios of old to young zone in MP5D44, CXD62-1 and CXD08-1 are 2.3, 3.4 and 13.7, respectively. The boundary depths of two-stage zone in MP5D44, CXD62-1 and CXD08-1 locate at 4.0 cm, 2.5 cm and 3.75 cm, respectively, and the time of iodine mutation in three crusts ranges from 17-37 Ma derived from 129I dating and Co empirical formula, which is consistent with the times of Cenozoic phosphatization events. The present study shows that the intensity of phosphatization is the main responsible for the distribution pattern of iodine in the crusts on the basis of the correlation analysis. Consequently, iodine is a sensitive indicator for phosphatization.

中亚造山带西准噶尔地区达尔布特蛇绿岩研究进展与展望

蛇绿岩是研究古大洋的主要载体和划分古板块边界的重要证据,记录了从大洋岩石圈的最初形成到最后洋盆闭合的诸多信息,是研究洋–陆转换过程的关键地质体。西准噶尔达尔布特蛇绿岩是北疆地区发育规模最大、最为典型的蛇绿岩带之一,相关研究近年来取得了系列成果。①在萨尔托海铬铁矿中发现金刚石等深部矿物群,从而对此前铬铁矿的浅部成矿理论提出了质疑。②在蛇绿岩中识别出前弧玄武岩,它是俯冲起始的地质记录之一。③蛇绿岩中存在古海山物质组分,其中玄武岩具有OIB特征。④萨尔托海铬铁矿是深部地幔预富集和浅部再富集的结果。⑤达尔布特蛇绿岩形成于俯冲有关的构造环境,并有地幔柱的参与。在取得进展的同时,也出现了一些新的科学问题和研究方向,主要包括深部物质循环过程、俯冲起始机制、陆壳增生机制和俯冲带型蛇绿岩成因等。

中西太平洋海山特征对延绳钓渔业和围网渔业黄鳍金枪鱼CPUE的影响

海山是海底重要的生物栖息地类型之一,是研究海洋生物多样性的热点区域。黄鳍金枪鱼(Thunnus albacares)广泛分布于中西太平洋,具有极高的生态和经济价值,然而,鲜有关于海山及其相关特征对黄鳍金枪鱼资源丰度和分布影响的研究。基于2010—2021年中西太平洋渔业委员会(Western and Central Pacific Fisheries Commission,WCPFC)汇总的延绳钓和围网渔业数据结合海山特征数据,采用广义加性模型(Generalized additive model,GAM)分析两种不同捕捞方式的黄鳍金枪鱼单位捕捞努力量渔获量(Catch per unit effort,CPUE)与海山相关特征之间的关系。结果表明,中西太平洋两种渔业方式的黄鳍金枪鱼渔获量主要来源于海山区域,海山特征对两种渔业黄鳍金枪鱼的CPUE均产生了极显著性影响(P<0.001)。在延绳钓渔业中,较高的CPUE出现在山顶深度、粗糙度、底面积和海山密度较小、坡度较缓的区域;而在围网渔业中,较高的CPUE则出现在粗糙度较小、山顶深度较大、底面积较大、较陡峭且密集的海山区域。研究探讨了中西太平洋海山特征对黄鳍金枪鱼不同群体的影响机制,为今后进一步探索黄鳍金枪鱼种群分布和资源丰度变化与海洋环境的关系提供了参考与新思路。

基于环境RNA研究海山效应对浮游细菌多样性和分布的影响

研究采用环境RNA技术探究西太平洋M4海山区细菌多样性,并与基于环境DNA技术的研究结果进行比较,解析细菌代谢活性特征。结果表明基于环境RNA和DNA技术检获的物种构成相似,但真光层中蓝细菌在RNA中的占比明显高于DNA,显示其高代谢活性;而α变形菌在RNA中的占比明显小于DNA,代谢活性低;γ变形菌在RNA中占比更大且随水层加深而增加。物种间关系网络复杂度随着水深的增加呈先升高后下降的趋势。基于RNA数据构建的网络较DNA数据网络简单,且随着水深增加变化趋势更加显著,去除蓝细菌后网络变化剧烈,而去除α变形菌对网络影响小。综上,研究基于环境RNA技术提供了海山区浮游细菌多样性及分布更加完整的认知,α变形菌在海山区多样性占比和其在群落中作用可能被高估。

中太平洋海山群玄武岩磷酸盐化特征及其对全岩地球化学的影响

大洋玄武岩是研究地幔不均一性、岩浆起源与演化的重要对象。然而,由于其长期与周围的海水相互作用,极易发生蚀变和次生变化。磷酸盐化是大洋玄武岩最常见的次生变化之一,会影响到其全岩地球化学成分,且目前仍没有去除磷酸盐化的有效方法。因此,研究磷酸盐化特征以及评估其对玄武岩全岩地球化学成分的影响至关重要。本文以中太平洋海山群(九皋和紫檀海山)玄武岩为研究对象,通过能谱面扫描元素分布图、主量元素以及微量元素揭示玄武岩的磷酸盐化特征,评估磷酸盐化对其全岩主微量元素的影响。面扫描元素分布图显示,中太平洋海山群玄武岩的磷酸盐化作用主要发生在玄武岩气孔和裂隙周围,以交代早期的碳酸盐化基质,形成细小的磷酸盐矿物,呈浸染状分布在玄武岩基质中为特点,并且磷酸盐化会不同程度地改变玄武岩的主量元素和微量元素成分:比如磷酸盐化会使玄武岩的MgO、CaO、Na_(2)O、MnO含量降低,K_(2)O和Fe_(2)O_(3)T含量升高,同时也会对相容元素(如Cr、Co、Ni等)、大离子亲石元素(Rb、Ba、Cs等)和稀土元素造成不同程度的影响。值得注意的是,在磷酸盐化过程中,玄武岩的Al_(2)O_(3)、SiO_(2)和高场强元素(Nb、Ta、Zr、Hf和Ti)几乎不受影响。

深海海底山引起的混响杂波联合预报方法

针对深海复杂海域的主动探测混响杂波干扰的联合工程预报问题,本文基于三维射线-简正波理论建立了深海海底山引起的混响杂波联合预报方法,将海底山当作一类具有强散射特征的体积散射源,提出了对海底山的体积散射函数在水平和垂直维度上进行网格划分的数值积分方法。研究了不同水平方位,不同地形条件下的海底混响和海底山杂波强度特征。实现了小起伏水平海底和海底山地形的深海海底混响和海底山杂波的统一预报。研究结果表明:海底山的体积散射源经过水平和垂直维度的划分后,可以和水平海底的小尺度散射过程形成有效耦合,而海底山杂波的时间尺度和包络强度分别受海底山的水平宽度和垂直高度影响。通过海上实验数据比对,验证了本文所提预报方法的准确性。

Classification of seamount morphology and its evaluating significance of ferromanganese crust in the central Pacific Ocean

Using the SeaBeam technology, the morphology of seamount and its relation to the formation of cobalt-rich crust in the central Pacific Ocean were surveyed during the cruise in 2003 for marine mineral resources. The result shows that seamounts can be divided morphologically into the spire seamount and the fiat topped seamount. These two types of seamount bear great differences in their landform, lithology and cobalt-rich crust. On the upper portion of the fiat topped seamount, the fiat top and the sharp escarpments are unfavorable to the growth of crust, and, consequently, the crusts here are mostly laminar or gravelly, their thicknesses generally show great variations, and the consecutive ore body often develops in its deep water region. On the spire topped seamount, however, the fiat area is small, and its gradient is constant without large variation from the top to the bottom. This favors the growth of cobalt-rich crust and often leads to consecutive tabular ore body of medium thickness, occurring on the spire topped seamount from the shallow water region to the deep water region. The cobalt-rich crust on the spire topped seamount is much better than that on the fiat topped seamount for the crust abundance, crust coverage and number of ore-occurrences within unit area. Furthermore, the crust on the spire topped seamount is rich in cobalt, nickel, manganese elements of high economic value. Because the crust with high quality ore often occurs in the shallow water region on the spire topped seamount, it can be mined and use more easily in the future.

Distribution Characteristics of Cobalt-rich Ferromanganese Crust Resources on Submarine Seamounts in the Western Pacific

Based on the survey data of five submarine seamount provinces （chains） in the Western Pacific, the distribution characteristics of cobalt-rich ferromanganese crust resources have been researched in this paper by using the relative reference data and applying the theories of hotspot and seafloor spreading. The main research results obtained are as follows： The Co-rich crust thickness in the study area is gradually increasing from east to west and from south to north having a negative correlation （r = -0.59） with longitude and a positive correlation （r = 0.48） with latitude. The crust thickness varying along longitude and latitude is influenced by the hotspot and seafloor spreading. The oceanic crusts and seamounts in the northwest part of the study area are older, and the crust resources are superior to those in the southeast part. In the depth of 〈1500 m, 1500-2000 m, 2000-2500 m in the study area, the cobalt crust thickness is respectively 5.45 cm, 4.34 cm and 3.55 cm, and in the depth of 2500-3000 m and 3000-3500 m, it drops respectively to 2.84 cm and 3.37 cm. The Co-rich crust resources are mainly concentrated in the seamount summit margins and the upper flanks in the depth of 〈2500 m. There is a strong negative correlation （r = -0.67） between the cobalt crust abundance and the slope of the seamount, 75 kg/m^2 and 50 kg/mz at the slopes of 0°-20° and 20°-34° respectively. Cobalt crusts are mainly distributed in the parts whose slopes are less than 20°. It is consistent with the fractal result that the slope threshold of cobalt crust distribution is 19°, and slopes over 20° are not conducive to the crust growth. The cobalt crusts of high grade are mainly enriched in the region within 150°E-140°W and 30°S-30°N in the Pacific, where there are about 587 seamounts at the depth of 3500- 6000 m and over 30 Ma of the oceanic crusts. The perspective area rich in cobalt crust resources is about 41×104 km^2 and the resource quantity is approximately 27 billion tons.

Distribution characteristics of seamount cobalt-rich ferromanganese crusts and the determination of the size of areas for exploration and exploitation

In 2001, the International Seabed Authority （ISBA） initiated the consideration relating to the Regulations for Prospecting and Exploration for Hydrothermal Polymetallic Sulphides and Cobalt-rich Ferromanganese Crusts in the Area at its 7th session. Since then, the consideration of the Regulations has been mainly focused on the size of areas to be allocated for exploration and exploitation of the crusts. This paper, based on the investigation data and the analysis of the distribution characteristics of the crusts, suggests a model for determining the size of areas for exploration and exploitation of the crusts, taking into account various factors such as production scale, crust thickness and grade, mineable area proportion, recovery efficiency, exploration venture, and so on. Through the modeling, the paper suggests that the exploration area （the area covered by each application for approval of a plan of work for exploration of cobalt-rich crusts） shall be 4 856 km2 and the exploitation area （the mine site area） shall be 1 214 km2, for 20 years of 1 million wet tonnes annual production.

Biomineralization of organic matter in cobalt-rich crusts from the Marcus–Wake Seamounts of the western Pacific Ocean

Organic matter in cobalt-rich crust （CRC） from the Marcus-Wake Seamounts of the western Pacific Ocean, Sample CM1D03, has been analyzed to understand the source, geochemistry and mineralization of organic matter, and the mineralization environment. Biomarkers, includingn-alkanes, isoprenoids, terpanes and sterols, have been detected in various layers of the CRC sample, using gas chromatography （GC） and gas chromatography-mass spectrometry （GC-MS）. The content of organic carbon （OC） and its stable isotope （δ13C）, and the combined features of the biomarkers show that the mineralized organic matter in CM1D03 CRC was mainly derived from microorganisms and lower plankton （e.g., bacteria and algae, respectively） from marine surface water, with some terrestrial higher plant components. The ratio of chloroform bitu-men ＂A＂： OC was high in the CRC, between 10.51 and 20.66, showing significant migration characteristics of n-alkanes. Four mineralization categories of organic matter were recognized based on GC chromatograms ofn-alkane molecules： （1） primitive type （bacteria and algae）, which is characterized by moderately mature ofn-alkanes preserving the original characteristics of the organic matter from microorganisms and lower plankton; （2） microbial degradation type, which is characterized by low contents ofn-alkanes and rising baseline in the chromatogram, with the ＂bulge＂ being the products of organic matter by biodegradation; （3） organic matter migration type, which is characterized by low carbon number ofn-alkanes withnC18 as the main peak carbon, without odd even predominance, and low concentrations of isoprenoids and hydro-carbons with high carbon number; and （4） organic matter hydrothermal type, which is characterized by relatively low concentration of small molecular weightn-alkanes, pristane, and phytane, accompanied by higher concentration ofn-alkanes with carbon number greater thannC18. This study shows that biomarkers can record controlling factors of mineralization and their variation.

Comparative Study of Magmatism in East Pacific Rise Versus Nearby Seamounts:Constraints on Magma Supply and Thermal Structure Beneath Mid-ocean Ridge

Major elements of 2202 basalts from the East Pacific Rise （EPR） and 888 basalts from near- EPR seamounts are used to investigate their differences in magma crystallization pressures and mantle melting conditions. Crystallization pressure calculation from basalts with 5.0wt%〈MgO〈8.0wt % shows that magma crystallization pressures beneath near-EPR seamounts are positively and negatively correlated with Nas and Fes, respectively. However, these correlations are indistinct in axial lavas, which can be explained by chemical homogenization induced by extensive mixing processes. In each segment divided by major transforms and over-lapping spreading centers （OSCs）, near-EPR seamount lavas have higher magma crystallization pressures, higher Fes and lower Nas than the EPR lavas, which indicate cooler lithosphere, lower degrees and shallower melting depths beneath near-EPR seamounts than the EPR. The correlations between magma crystallization pressures and melting conditions beneath near-EPR seamounts imply that the source thermal state controls the melting degree and melt flux, and then melting process controls the shallow lithosphere temperature and magma crystallization depth （pressure）. The cooler mantle sources beneath near-EPR seamounts produce a lower degree of melting and a less robust magma supply, which results in a deep thermal equilibrium level and high magma crystallization pressure. The magma crystallization pressure decreases significantly as spreading rate of the EPR increases from ~80 mm/year in the north （16~N） to ~160 mm/year in the south （19~S）, while this trend is unobvious in near-EPR seamounts. This suggests that the magma supply controlled by spreading rate dominates the ridge crust temperature and magma crystallization depth, while the near-EPR seamount magma supply is not dominated by the axial spreading rate. Because most seamounts form and gain most of their volume within a narrow zone of 5-15 km from ridge axis, they provide good constraint on magma supply and thermal structure beneath the EPR. High magma crystallization pressures in seamounts indicate dramatic temperature decrease from the EPR. The crystallization pressures of seamount lavas are well correlated with mantle melting parameters but in a blurry relationship with axial spreading rate. Despite the adjacency of the EPR and nearby seamounts, the thermal structure beneath the near-EPR seamounts are controlled by their own magma supply and conductive cooling, chemically and thermally unaffected by magmatism beneath the ridge axis.

The first record of Ophioleila elegans (Echinodermata:Ophiuroidea) from a deep-sea seamount in the Northwest Pacific Ocean

The rare ophiuroid species, Ophioleila elegans, was collected by the submersible Jiaolongfrom 1 660 m depth on the Caiwei Guyot located in the Magellan Seamount Chain in the Northwest Pacific Ocean. This is the first published record of this species since the types were described from similar habitat off Hawaii. We provide more detailed morphologic characteristics of arm skeleton and a phylogenetic analysis based on CO 1 sequences. Both morphology and phylogeny results suggest that the genus Ophioleila is more closely related to Ophiactids than Hemieuryalids.

Ecological functions of uncultured microorganisms in the cobaltrich ferromanganese crust of a seamount in the central Pacific are elucidated by fosmid sequencing

Cobalt-rich ferromanganese is an important seafloor mineral and is abundantly present in the seamount crusts. Such crusts form potential hotspots for biogeochemical activity and microbial diversity, yet our understanding of their microbial communities is lacking. In this study, a cultivation-independent approach was used to recover genomic information and derive ecological functions of the microbes in a sediment sample collected from the cobalt-rich ferromanganese crust of a seamount region in the central Pacific. A total of 78 distinct clones were obtained by fosmid library screening with a 16S rRNA based PCR method. Proteobacteria and MGI Thaumarch-aeota dominated the bacterial and archaeal 16S rRNA gene sequence results in the microbial community. Nine fosmid clones were sequenced and annotated. Numerous genes encoding proteins involved in metabolic functions and heavy metal resistance were identified, suggesting alternative metabolic pathways and stress responses that are essential for microbial survival in the cobalt-rich ferromanganese crust. In addition, genes that participate in the synthesis of organic acids and exoploymers were discovered. Reconstruction of the metabolic pathways revealed that the nitrogen cycle is an important biogeochemical process in the cobalt-rich ferromanganese crust. In addition, horizontal gene transfer （HGT） events have been observed, and most of them came from bacteria, with some occurring in archaea and plants. Clone W4-93a, belonging to MGI Thaumarch-aeota, contained a region of gene synteny. Comparative analyses suggested that a high frequency of HGT events as well as genomic divergence play important roles in the microbial adaption to the deep-sea environment.

Archaeal community structure in sediments from a seamount in the Mariana Volcanic Arc

Seamounts are subsurface mountains in the ocean. Examination of the abundance and distribution of Archaea in seamount ecosystems may provide a better understanding of their ecological functions. Most studies of marine archaeal assemblages in seamount area have focused on hydrothermal vents or ferromanganese crusts. We investigated the archaeal communities from a seamount of the Mariana Volcanic Arc, in the tropical western Pacific Ocean by using high-throughput sequencing. Thaumarchaeota was dominant in the sediments of all sample stations. Community diversity and species richness were greatest at stations near the top of the seamount, and lowest at the deepest station. One sample station on the steep southeast slope that faced the Yap-Mariana trench had a unique composition of Archaea. In summary, depth has an important influence on archaeal community structure, and the geographic properties and sediment characteristics may explain the unique distribution patterns of Archaea in this seamount. This study provides a foundation for future research on Archaea in seamounts.

Microtexture and Distribution of Minerals in Hydrothermal Barite-Silica Chimney from the Franklin Seamount, SW Pacific: Constraints on Mode of Formation

An extinct hydrothermal barite-silica chimney from the Franklin Seamount of the Woodlark Basin, in the southwestern Pacific Ocean, was investigated for mineral distribution and geochemical composition. Six layers on either side of the orifice of a chimney show significant disparity in color, mineral assemblage and major element composition. Electron microscope（SEM） images reveal that the peripheral wall of the chimney is composed of colloform silica, suggesting that incipient precipitation of silica-saturated hydrothermal fluid initiated the development of the chimney wall. Intermediate layers, between the exterior wall and the inner fluid-orifice, dominate with barite and sulfides. Low Sr-to-Ba ratios（SrO/BaO = 0.015–0.017） indicate restricted fluid-seawater mixing, which causes relatively high-temperature formation of the intermediate layers. Whereas the innermost layer bordering the chimney orifice is characterized by more silica and a higher Sr-to-Ba ratio（SrO/BaO = 0.023）, could have formed due to a paragenetic shift from a high-temperature active phase to a cooler waning stage of formation. A paragenetic shift is also probably responsible for the change in mineral formation mechanism that resulted in the textural variation of barite and colloform silica developed during different growth phases of this barite-silica chimney.

Physical oceanography of the Caroline M4 seamount in the tropical Western Pacific Ocean in summer 2017

Physical oceanography plays an important role in the formation of submarine sediments,and the distribution of nutriments and biocenoses in seamounts.The M4 seamount is located in the Caroline Island Ridge of the Western Pacific Ocean.The physical properties around M4 seamount are preliminarily analyzed based on the in-situ data obtained in summer 2017 in Caroline M4 seamount and open-sourced data.We found that the water in the upper 200 m is controlled by the westward North Equatorial Current(NEC),while the water between 300-1000 m is dominated by the eastward North Equatorial Undercurrent(NEUC).The current direction fluctuates significantly below 300 m at upstream stations.At the same depth of the lee sides,the current direction changes with the distance from seamount.These are likely caused by the obstacle of M4 seamount.The calculation results show that there is an anticyclonic cap above M4 seamount caused by tidal rectification.Tidal currents in M4 seamount are squeezed by the topography and amplified,and the amplified tidal currents play a dominant role in M4 seamount.First,the circulation system generated by the interaction of the amplified tidal current and M4 seamount drives the upward/downward movement of the isotherms.Secondly,the thickness of the surface turbulent layer is changed with the tidal phase.Thirdly,high turbulent diffusivities are found in the bottom of M4 seamount,and these are most likely attributed to the turbulent mixing induced by the mutual effect between semidiurnal tidal currents and steep bathymetry.This article of physical oceanography provides scientific basis for further analysis of the distribution of biological community and deposition mechanism in M4 seamount.

Accration and Subduction of Seamounts in West Junggar

Recently,through implementation of the National Nature Science Foundation of China （No.41303027） and Special Fund for Basic Scientific Research of Central Colleges （310827153506,310827153407,2014G1271058）,we focused on basalts in Darbut and Karamay ophiolitic melanges in West Junggar which is a part of the Central Asian Orogenic Belt,and made some advances as follows.

Paragorgia papillata sp.nov.,a new bubblegum coral(Octocorallia:Paragorgiidae)from a seamount in the tropical Western Pacific

A new species of bubblegum coral,Paragorgia papillata sp.nov.,discovered from a seamount located on the Caroline Ridge at the water depth of 858 m,is studied using morphological and molecular approaches.The new gorgonian is white-colored,uniplanar with prominent autozooids,and measures about670-mm high and 690-mm wide.The genetic distance and phylogenetic analysis showed that P.papillata sp.nov.was closely related to P.coralloides Bayer,1993,but the former differs morphologically from the latter by its prominent calyces(diameter 2.0-4.0 mm and height 1.5-3.0 mm vs.both diameter and height about 1 mm),white cortex(vs.pink),regular 8-radiates in surface cortex(vs.mostly 8-radiate derived globular radiates)and highly ornate medullar spindles(length 185-400μm vs.no more than 150μm).P.papillata sp.nov.is the third known white-colored species of the genus,and the fifth species found in the tropical Western Pacific.

Establishment of Alloptilella splendida gen.et sp.nov.and resurrection of Scytalium veneris(Thomson&Henderson,1906),two sea pens(Cnidaria:Pennatulacea)from seamounts in the tropical Western Pacific

Sea pens are a highly specialized and morphologically distinct group of octocorallians,but many taxa were poorly described and their phylogenetic relationships are still poorly known.We describe two species of sea pens collected from the tropical Western Pacific:Alloptilella splendida gen.et sp.nov.and Scytalium veneris(Thomson&Henderson,1906).Alloptilella splendida gen.et sp.nov.accords with the definition of the recently resurrected genus Ptilella Gray,1870 in most characters,but differs from the latter in the arrangement of autozooids and the location of mesozooids.The new species mostly resembles Pennatula naresi K(o|")lliker(1880),but differs by the location of me sozooids and the reddish color of sclerite s surrounding siphonozooids.The generic separation is also well supported by their genetic distances and the molecular phylogenetic trees constructed by the concatenated mtMutS-COI-28 S,where Alloptilella clustered with Scytalium Herklots,1858 and formed a clade with the cluster of Ptilella and Distichoptilum.Scytalium veneris,usually considered as a junior synonym of Scytalium sarsii Herklots,1858,is resurrected by recognizing their distinctive differences.This is the first record of Scytalium veneris outside its type locality,and the phylogenetic analysis indicates that Scytalium is a monophyletic group.Both the families Pennatulidae and Virgulariidae are polyphyletic,and more morphological and molecular data are needed to clarify the phylogenetic positions of pennatulacean families and genera.