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The fossil record of terrestrialization documents notable shifts in the environmental and physiological tolerances of many animal and plant groups. However, for certain significant components of modern freshwater and terrestrial environments, the transition out of marine settings remains largely unconstrained. Ostracod crustaceans occupy an exceptional range of modern aquatic environments and are invaluable palaeoenvironmental indicators in the fossil record. However, pre-Carboniferous records of supposed non-marine and marginal marine ostracods are sparse, and the timing of their marine to non-marine transition has proven elusive. Here, we reassess the early environmental history of ostracods in light of new assemblages from the late Silurian of Vietnam. Two, low diversity but distinct ostracod assemblages are associated with estuarine deposits. This occurrence is consistent with previous incidental reports of ostracods occupying marginal and brackish settings through the late Silurian and Devonian. Therefore, ostracods were pioneering the occupation of marginal marine and estuarine settings 60 Myr before the Carboniferous and they were a component of the early phase of transition from marine to non-marine environments.

To the north of Hanoi, about a day's drive by car, lies Ha Giang Province, the northernmost region of Vietnam. Ha Giang is remote from the hustle and bustle of daily life, and beyond its eponymous provincial capital towards the border with China, mountains rise quickly to Quan Ba, ‘Heaven's Gate’. The mountains form an uneven landscape of steep‐sided karst rising from deep river‐cut gorges and form a formidable barrier on the northern frontier of Vietnam. Beyond ‘Heaven's Gate’ lies the little travelled region of Dong Van, with its majestic mountains of Palaeozoic strata rising precipitously to the sky. Here, a century ago, the French geologists Henri Mansuy and Jacques Deprat documented early finds of fossils from lower Palaeozoic strata on the border with China.

In this study, we investigated ostracod assemblages from the Co To Islands in northeastern Vietnam. We identified 77 ostracod species belonging to 46 genera in nine surface sediment samples and recognized three biofacies (I, II, and III) based on Q-mode cluster analysis. The dominant species of biofacies I and II were Aurila hataii, Loxoconcha japonica, and Xestoleberis hanaii, which commonly occur in seaweed beds from southern China to Japan. This is the first report on the ostracod assemblage from the open-sea area in northeastern Vietnam. We clarified that the ostracod assemblages in the Gulf of Tongking, including northern Vietnam, have a strong biogeographical relationship with East Asia seas. A new species, Loxoconcha cotoensis sp. nov., was described herein from the Co To Islands (http://www.zoobank.org/NomenclaturalActs/41d3fb9f-ae17-4215-82c1-0874a8bf1a30, last access: 3 June 2019).

The local coordination environments of Ti in Cretaceous–Paleogene (K–Pg) from Stevns Klint and Devonian–Carboniferous (D–C) boundary from western part of Cat Co Beach on Cat Ba Island sediments are studied by K-edge X-ray absorption fine structure (XAFS) in order to provide local atomic information by X-ray absorption near edge structure (XANES) and coordination environments by extended X-ray absorption fine structure (EXAFS). Ti K-edge XAFS spectra in bulk part of K–Pg and D–C boundary sediments are compared with those of reference materials such as TiO2 (rutile, anatase and brookite polymorph), CaTiO3, MgTiO3, SrTiO3, PbTiO3, moldavite-brownish, moldavite-green, suevite from Ries crater, impactite, obsidian and Kilauea volcanic glass. The shapes of XANES and EXAFS spectra in K–Pg sediments are similar to those in suevite. Suevite was formed under meteorite impact and its glass component was formed under high temperature and high pressure. Similarities of XANES and EXAFS between K–Pg sediments and suevite indicate that formation process of K–Pg sediments is related to a meteorite impact event. On the other hand, the shape of XANES spectrum in D–C sediments is similar to those in anatase and obsidian. However, the shape of EXAFS spectra in D–C sediments is similar to those in obsidian, rather than anatase. Coordination environments of Ti in D–C sediments suggest that the original glass-like local environments were changed to anatase-like local environments by devitrification. This leads to the conclusion that the analysis of the atomic coordination environments of Ti in boundary sediments can in principle be used as a marker of large meteorite impact, though this Ti local environmental information is actually lost due to the devitrification phenomenon to anatase by quenching process or long-time diagenesis. This may be compensated by the XAFS analysis of Zr because local coordination environments of Zr in same analytical point of K–Pg sediments were not affected by diagenesis (Tobase et al., J Miner Petrol Sci 110:88–91, 2015a).

The Devonian-Carboniferous transition (359 Ma) was a time of extreme climate and faunal change and is associated with the end-Devonian biodiversity crisis. The transition is characterized by transgressive/regressive cycles, which culminated in the onset of widespread ocean anoxia (the Hangenberg Black Shale event) and a remarkable sea-level fall close to the Devonian-Carboniferous boundary (the Hangenberg Sandstone event); together these are known as the Hangenberg Crisis. The Hangenberg Crisis has been documented around the globe, but the trigger mechanisms for its onset remain unknown. The Pho Han Formation on Cat Ba Island in northeastern Vietnam preserves the Devonian-Carboniferous transition and Hangenberg Crisis in a sediment- starved basinal facies on the South China carbonate platform. Although the Hangenberg Black Shale event is generally preserved as a discrete anoxic interval in Devonian-Carboniferous boundary sections of North America and Europe, the Pho Han Formation records sustained dysoxic/anoxic conditions from the Famennian (Upper Devonian) through the Tournasian (early Carboniferous), with severe anoxia (approaching euxinia) throughout the Hangenberg Black Shale event interval (as determined by trace element proxies, increased total organic carbon, and framboidal pyrite distributions). There is also significant mercury enrichment corresponding to the Hangenberg Crisis in the Pho Han Formation. The isolated paleogeography of the region suggests that the mercury is most likely sourced from distal volcanic emissions. It is therefore possible that large-scale volcanic activity acted as a trigger mechanism for the Hangenberg Crisis and biodiversity drop at the Devonian- Carboniferous transition, similar to other major mass extinction events.

Two new graptolite assemblages are identified from discrete intervals within the Phu Ngu Formation, Na Ri District, Bac Kan Province, north-east Vietnam. The graptolites occur in laminated mud/siltstones thought to be distal turbidite deposits. A low-diversity diplograptid sensu lato assemblage occurs in mud-rich layers that are interlaminated with silty and sandy horizons containing the dendroid graptolite Dictyonema sp. This level also contains orthoconic nautiloids and conulariids. A few metres stratigraphically above, a second more diverse graptolite assemblage comprises a single Dicellograptus, tentatively identified as D. flexuosus, together with Climacograptus dorotheus and Orthograptus truncatus pauperatus in mud and silt laminae that also yield brachiopods, orthoconic nautiloids, conulariids, fragmentary trilobites, and ostracods. The ostracods include the first East Asian occurrence of the typically Baltic genus Kinnekullea, and we describe the new species Kinnekullea gaia. The graptolites suggest a Late Ordovician Katian age, most probably in the Dicranograptus clingani Biozone, this being older than previous biostratigraphical constraints on the Phu Ngu Formation.

Ba River originates from the Ngoc Linh mountain ranges, NW of Kontum massif and flows into the East Sea from the Da Rang estuary. The Ba River basin (Da Rang river) is considered as the means of transport and storage of products from the Kontum massif resulted following weathering, erosion or deformation processes either by natural causes or the regional thermo-tectonic events. A total of 122 zircon grains separated from the Ba River basin sediments are selected for U-Pb isotopic age dating by LA-ICP-MS method. Among the 122 samples, 114 are concordant, forming 3 major age groups, including middle-Late Cretaceous (105–85 Ma), Middle Permian - Late Triassic (270–211 Ma), Late Ordovician - Early Silurian (455–424 Ma). A few samples show ages scattering from 1470 to 970 Ma (Mesoproterozoic), and one sample shows a value of 2383±24 Ma (Paleoproterozoic). The acquired U-Pb zircon ages may reflect 3 major thermo- tectonic stages in the formation and evolution of the Kontum Massif from the Early Paleoproterozoic till middle-Late Cretaceous, with the most significant time being Middle Permian (270 Ma)-Late Triassic (211 Ma) (97 over 122 samples, e.g., 79,5%), corresponding to the period of convergence, collision and orogeny of the Indosinian block.

In this report, we describe the first discovery of two living ostracods from the Japanese archipelago, Sinocytheropteron ignobile and Sinocytheridea impressa, which are typically continental faunal elements from China, during our research on the distribution of ostracod assemblages in the Ariake and Yatsushiro Seas in southwest Japan. The (palaeo-) biogeographical data from recent and fossil records indicate that S. ignobile and S. impressa migrated through land bridges during past decreases in sea levels. We also discovered Xestoleberis ryukyuensis, which has been reported from the Ryukyu Islands; its discovery in our study area indicates the current northernmost distribution of the species and suggests that it migrated from the Ryukyu Islands to the study area using the Tsushima Warm Current, a branch of the main Kuroshio Current. This evidence suggests that the migration of shallow-marine ostracods between the continents and their adjacent islands affect not only global oceanic current but also global decreases in sea levels and the (palaeo-) geography of adjacent seas. Thus, ostracods living within the continental coasts provide powerful evidence for reconstructing the connection between the continent and its adjacent islands.

The genusNeomonoceratina, which dominated the ostracod assemblage in the uppermost part of the Akasaki Formation (Miroku Group) of the Kyushu Island, Japan, is associated with the benthic foraminiferAmmonia cf.beccarii, molluscaTerebralia? sp. andAnomiasp., and the oogonium of Charophyceae, indicating a marine-to-brackish estuarine environment involving inflowing freshwater. This is the first record of Eocene coastal-estuarine ostracods from the eastern margin of the Eurasian continent and demonstrates that different pre-Neogene coastal-estuarine ostracod assemblages flourished in this region. The assemblages comprised five ostracod species (including one novel species) assigned to the generaNeomonoceratina,Paijeiborchella,PropontocyprisandParakrithella. These species exhibited genus-level links with the Eocene borehole cores along the continental shelf of the East China Sea and other areas of Kyushu. Fossil data of characteristic Eocene coastal-estuarine genera collected worldwide indicate that different characteristic genera inhabited each region. For example,Neomonoceratinaoriginated on the Indian subcontinent by the Early Paleocene period at the latest, along with the northern drift of the Indian subcontinent. These species subsequently diversified west and east with the equatorial current and counter-current via the Tethys and reached the eastern margin of the Eurasian continent among the various eastwards-migrating species, where one genus ultimately adapted to the coastal-estuarine environment. Notably, the coastal-estuarine ostracod assemblage of the eastern margin of the Eurasian continent differs completely from that of the Tethys during the Eocene period. Our results suggest that coastal-estuarine ostracod assemblages are a powerful tool for palaeogeographic reconstruction.

The Triassic Taho Formation crops out in Taho, Shirokawa Town, Seiyo City, Ehime Prefecture, Southwest Japan. The formation is newly divided into the Tahogawa and Sakuragatouge members. The Tahogawa Member consists mainly of partly dolomitized light-, dark-, brownish-gray and black bedded limestones, and yields abundant Early to Middle Triassic conodonts, ammonoids, gastropods, bivalves, brachiopods and fish remains. The Sakuragatouge Member is dominated by brownish gray lenticular conglomeratic limestone and massive gray and white limestones that contain Middle to Late Triassic conodonts, gastropods, bivalves, echinoids and fish remains. In the Tahogawa Member, conodont assemblages are composed of 13 genera and 45 species, including three new species: Neospathodus arcus Maekawa sp. nov., Novispathodus shirokawai Maekawa sp. nov., and Nv. tahoensis Maekawa sp. nov. The member is divided into five conodont zones in ascending order: the Ns. dieneri Zone, the Ns. cristagalli Zone, the Nv. ex gr. waageni Zone, the Nv. pingdingshanensis Zone and the Nv. brevissimus Zone. The Nv. ex gr. waageni Zone contains three conodont subzones (the Eurygnathodus costatus Subzone, the Guangxidella bransoni Subzone and the Scythogondolella milleri Subzone), and the Nv. brevissimus Zone includes the Icriospathodus collinsoni Subzone. The conodont biostratigraphy of the member indicates a late Dienerian to early Spathian age, and correlates with that of Tethyan and Panthalassean sections. The Induan-Olenekian boundary is indicated by the first occurrence of Nv. ex gr. waageni. The Smithian-Spathian boundary is immediately below or intercalated within the Nv. pingdingshanensis Zone.

Two Late Pennsylvanian conodont species, Gondolella sublanceolata Gunnell and Idiognathodus sulciferus Gunnell, were extracted from limestone boulders in the Mizuboradani Valley, Fukuji district, central Japan. These provide the first evidence of Missourian (Kasimovian) cosmopolitan conodonts in the Akiyoshi and Hida Gaien belts, Inner Zone of Japan. The limestone boulders might be derived from the Ichinotani Formation and/or from limestone clasts in conglomerates of the Permian Sorayama Formation that crop out in the Mizuboradani Valley.

Cheilostome bryozoans (Phylum Bryozoa; Order Cheilostomata) originated in the latest Jurassic but remained at low diversity until the late Albian–early Cenomanian, when they began an explosive radiation that has continued to the present day. Most knowledge of Late Cretaceous cheilostomes comes from Europe and the USA from deposits associated with the western Tethys Ocean. Only a few previous records of Cretaceous bryozoans exist from the margin of eastern Asia in the NW Pacific. We examined material from four localities of early– middle Campanian age in the Himenoura Group, Shimokoshikijima Island, Kagoshima Prefecture, southern Kyushu, Japan, and detected six cheilostome species but no cyclostomes. Two species were relatively common. For one of these, we erect the new genus Kenocharixa and describe a new species, Kenocharixa kashimaensis; we also transfer Charixa goshouraensis Dick, Komatsu, Takashima, and Ostrovsky and Conopeum stamenocelloides Gordon and Taylor to Kenocharixa. We describe the other common species as Marginaria prolixa sp. nov. We detected four species as a single specimen each and identified them only to genus (Charixa sp. A) or listed them as Incertae sedis (A, B and C). Among the six cheilostomes, five are primitive anascan-grade (malacostegan) species and one is an anascan-grade neocheilostome. Compared to Campanian–Maastrichtian bryozoan faunas in Europe and the USA, the Himenoura fauna is low in diversity and morphological disparity, with no cribrimorph or ascophoran species detected. Previous researchers have suggested that the NW Pacific biota became isolated from that of the Tethys in the latest Aptian–middle Albian interval. We advance the hypothesis that the Late Cretaceous bryozoan fauna in the NW Pacific is a low diversity relict of the fauna present when this isolation occurred. While Tethyan cheilostome lineages underwent a major radiation associated with the origins of cribrimorph and ascophoran frontal shields, the NE Pacific lineages failed to diversify at the same rate and remained at low diversity and disparity. Testing this hypothesis will require much further sampling in Cretaceous deposits along the margin of East Asia.

A newly discovered trilobite from the Naidaijin Formation in the Kurosegawa Terrane of southwest Japan is referred to Toxophacops (Atopophacops) fujiwara sp. nov. The trilobite occurs in strata 2 m below a level with detrital zircons that yield an age of 383.9±4.4 Ma that is likely Givetian (late Mid-Devonian). Elsewhere, Early to Mid-Devonian trilobite species of T. (Atopophacops) and T. (Toxophacops) have been recorded from the Nakazato Formation of the South Kitakami Terrane of northeast Japan, and from the Zhusilenghaierhan region of western Inner Mongolia, North China. The new trilobite species extends the geographical range of the phacopid subfamily Echinophacopinae, and supports the affinities of some Devonian Japanese trilobites with those of north China. The occurrence of Toxophacops in the Lower Member of the Naidaijin Formation, combined with other trilobite evidence, confirms a clear biostratigraphical distinction between the Lower Member (upper Lower and Middle Devonian) and Upper M...

The lower Palaeozoic marine succession of NE Vietnam accumulated on the South China plate. Despite historical works dating to French colonial times, the stratigraphy and palaeontology of the succession is poorly constrained. Chief amongst the lower Palaeozoic lithostratigraphical divisions is the Than Sa Formation, a c. 1200 m thick succession of clastic rocks of Cambrian and early Ordovician age. Newly collected graptolites (including Rhabdinopora? sp. and Tetragraptus approximatus) from the upper part of the formation identify strata assignable to the Tremadocian and Floian stages of the Lower Ordovician. The same succession also probably records the Cambrian–Ordovician boundary. Our analysis identifies one or more intervals of graptolite-bearing laminated mudstones in the upper part of the Than Sa Formation that may be widespread in NE Vietnam during the early Tremadocian.

The first plant microfossil assemblage from the Si Ka Formation of the Song Cau Group, northern Vietnam is reported. It is composed of cryptospores in dyads and tetrads, trilete spores, tubular remains consisting of an association of smooth, banded, and externally thickened tubes, and cuticle-like fragments. The biostratigraphic assemblage of sporomorphs indicates a late Silurian (late Ludfordian) to Early Devonian (early Lochkovian) age. Further comparison with coeval reports using the characteristic features of the assemblage confines their age to the late Ludlow (late Ludfordian) to early Přidoli. This report presents the oldest spore assemblage from Vietnam and contributes to a broader understanding of its paleo-landscape during the late Silurian.

To clarify the process of producing the striations in the trace fossil Asteriacites, we observed the behavior of living ophiuroids and asteroids in aquariums. When ophiuroids stopped crawling, they buried themselves shallowly in the substratum, removing substratum under their arms and discs by using their tube-feet. The basal-arm tube-feet produce well spaced, fine, parallel striations that are perpendicular to the arm axis. The oral tube-feet produce fine, radial striations in the central depression. When the ophiuroids resumed crawling, they raised their disc and four arms above the substratum and dragged one arm backward. The one backward arm erased the striations, and parallel fine striations remained in four arm depressions. Similarly, asteroids also produced wide and shallow striations perpendicular to the arm axis by tube-feet movement. When the asteroids started to move again, they bulldozed the substratum under the one preceding arm, where the striations were erased. Since the asteroids...

This article presents a rather well-preserved radiolarian fauna recovered from black siliceous mudstone occurring in the Ky Cung River section 02 (KC02) of the Bac Thuy Formation, Lang Son Province, northeastern Vietnam. The KC02 section has been regionally correlated on the basis of the first appearance of the diagnostic Spathian ammonoid Tirolites . The ammonoid assemblage associated with radiolarians indicates that the black mudstone sample is early Spathian in age (Late Olenekian). The radiolarian fauna is characterized by a very low diversity of entactinarians of the family Hindeosphaeridae and of to another unidentified family, and by the absence of nassellarians. Here we describe two new species of entactinarians, Parasepsagon primitivus nov. sp. and Eptingium ? reticulatum nov. sp. The composition of the fauna suggests that the beginning of diversification of Mesozoic-type radiolarians occurred at the beginning of the Spathian on the eastern margin of the tropical Tethys.

Silicified beyrichiocopid and podocopid ostracods from limestone nodules derived from the middle part of the Ichinotani Formation within the Hida Gaien Terrane of central Honshu Island, Japan, are associated with fusulinid foraminifera that indicate strata of the middle Moscovian (Pennsylvanian, Carboniferous). This is a rare record of ostracods from the Palaeozoic of Japan and the first systematic description of ostracods from the Carboniferous of the Hida Gaien Terrane. The fauna comprises six ostracod species (two new) assigned to the generaAmphissites,Kirkbya,Bairdia,AechminaandHealdia, and additional material of possible cavellinids. The numerical dominance of ornamented beyrichiocopids such asKirkbyaandAmphissites, along with smaller numbers of smooth podocopids such asBairdia, indicates an ‘Eifelian mega-assemblage’ ecotype (sensuG. Becker), that is typical of mid Palaeozoic shallow marine, high-energy environments in a fore-reef ecosystem.

We obtained zircon U—Pb ages using LA-ICP-MS for an acidic tuff bed in the upper part of the Akasaki Formation, a basal unit of the Eocene sequence in the Amakusa area, Kumamoto Prefecture, Japan. The U—Pb age of 49.1±0.4 Ma (95% confidence interval) suggests a late early Eocene age. Our result is important for biochronological assessment of the land mammal fauna of the Akasaki Formation. The new age date supports the correlation of the Akasaki mammal fauna with the Bridgerian North American Land Mammal Age.

A numerically small graptolite assemblage from the Long Dai Formation at Lam Thuy village, southwestern Le Thuy district, Quang Binh Province, central Vietnam, includes Oktavites spiralis (Geinitz). The relative abundance of this species in the assemblage, coupled to its occurrence with Oktavites bodentoerlensis Loydell, identifies the lower Silurian (Llandovery Series, Telychian Stage) spiralis graptolite Biozone. Identification of the new locality at Lam Thuy enhances the dataset of Silurian graptolite-bearing localities in central Vietnam and advertises the wide utility of graptolite assemblages for biostratigraphical correlation of lower Palaeozoic strata in northern and central Vietnam.

The Smithian–Spathian boundary is indicated by the first occurrence of the ammonoid Tirolites cf. cassianus in the Olenekian Bac Thuy Formation, northeastern Vietnam. The boundary is intercalated within organic-rich dark gray mudstone that accumulated under anoxic to dysoxic conditions in the An Chau and Nanpanjiang Basins on the South China Block. In Lang Son area, three conodont zones, Novispathodus ex gr. waageni, Novispathodus ex gr. pingdingshanensis, and Icriospathodus collinsoni, are recognized in the formation. The Smithian–Spathian boundary is intercalated within N. ex gr. pingdingshanensis conodont Zone. The positive excursion inδ13C with values increasing from around − 2.3‰ to + 5.7‰ was recorded in the uppermost Smithian Xenoceltites variocostatus ammonoid beds and N. ex gr. pingdingshanensis conodont Zone. The δ13C values decrease across the Smithian–Spathian boundary. These δ13C isotopic patterns are correlated with well-known positive excursions around the Smithian–Spathian boundary globally.

The Tahogawa Member of the Triassic Taho Formation in Southwest Japan consists predominantly of light, dark, and brownish gray bedded limestones and contains abundant Lower to Middle Triassic conodonts. The late Smithian to early Spathian sequence of the Tahogawa Member is divided into five conodont zones, in ascending order: Novispathodus ex gr. waageni, Nv. pingdingshanensis, Nv. brevissimus, Triassospathodus symmetricus, and Tr. homeri. The Scythogondolella milleri Subzone of the Nv. ex gr. waageni Zone contains a late Smithian Anasibirites bearing ammonoid bed. The carbon isotope (δ13Ccarb) curve for the late Smithian to early Spathian shows a rapid excursion with values increasing from ~0.11‰ to ~5.88‰ (VPDB). The rise in δ13Ccarb starts in the upper part of the Nv. ex gr. waageni Zone and continues into the overlying Nv. pingdingshanensis Zone. The δ13Ccarb values peak in the Nv. pingdingshanensis Zone at 5.88‰, and subsequently decrease to 1.13‰ in the Tr. symmetricus Zone. The carbon cycle perturbation recorded in the Tahogawa Member corresponds to the late Smithian to early Spathian global carbon isotope positive and following negative excursions reported from the Tethyan, Panthalassan, and Boreal regions. The Smithian–Spathian boundary is probably located within the Nv. pingdingshanensis Zone of the Tahogawa Member, coincident with the decreasing limb of the carbon isotope perturbation. The combination of δ13Ccarb and conodont stratigraphic data enable us to correlate between the eastern Tethys and Panthalassan regions.

Not even Hollywood could dream of a place so magical as Kyushu. The southern-most of the four major islands of the Japanese archipelago, this is a land of volcanoes, dinosaurs, and the last stand of the Samurai. And for good measure, James Bond visited here too, in the 1967 film You Only Live Twice. The final explosive scenes of that film featured the destruction of megalomaniac Ernst Stavro Blofeld's headquarters hidden inside the crater of one of Kyushu's most emblematic volcanoes, Shinmoedake. Kyushu also straddles the largest geological structure in Japan, the Median Tectonic Line (MTL) that runs from the western approaches of the island to the central part of Honshu. The MTL has been active since the Cretaceous, and the sedimentary basins formed along its line in Kyushu contain some of Japan's most famous dinosaur finds. The MTL also defines a fundamental divide between the geological histories of the terranes north and south of its line, a history that takes us back to the origins of the Japanese archipelago half a billion years ago.

The Early Triassic conodonts Eurygnathodus costatus Staesche, E. hamadai (Koike), Neospathodus cristagalli (Huckriede), and Ns. pakistanensis Sweet are newly reported from the upper part of the Lang Son Formation in Lang Son City, northeastern Vietnam. This association and particularly E. costatus and E. hamadai indicate the lower Smithian (lower lower Olenekian). Thus, the geological age of the upper part of the Lang Son Formation ranges from Induan to early Olenekian, and the stage boundary lies within the upper part of the formation.

Newly collected graptolites from the Co To Formation, Co To archipelago, NE Vietnam, comprise assemblages indicative of two biostratigraphical levels within the lower Silurian, Llandovery Series, Telychian Stage: the co-occurrence of Spirograptus turriculatus and Torquigraptus proteus? suggests an interval most likely within the upper part of the Spirograptus turriculatus Biozone or ‘Monograptus’ crispus Biozone, whilst Oktavites spiralis and Monoclimacis cf. subgeinitzi identify the Oktavites spiralis Biozone. The graptolites provide important biostratigraphical evidence for the age of the upper part of the lower Co To Formation, biostratigraphical ties between the NE Vietnamese succession of the Bac Bo Region and graptolite assemblages of the Long Dai Formation in the Viet-Lao Region of central Vietnam, and include the new species Monograptus hamulus sp. nov. co-occurring with S. turriculatus, which is perhaps an ancestral form to the later Telychian species Monograptus drepanoformis. We also report the first chitinozoans, including Belonechitina, from the Co To Formation.

On Cat Ba Island in northeastern Vietnam, the Devonian to Carboniferous (D–C) transition consists mainly of ramp carbonates intercalated with black shale beds (Beds 1 to 176) in the Pho Han Formation and is one of the few records of the D–C transition of the eastern Paleotethys. The three main facies of the sequence are Facies 1 (alternations of whitish gray to gray limestone and marl), Facies 2 (calcirudite, Bed 115b), and Facies 3 (alternations of dark gray limestone and organic-carbon-rich black shale, Beds 115c–120 and 126–129). The latest Famennian (Siphonodella praesulcata Subzone) conodont assemblage of S. praesulcata, Palmatolepis gracilis, Palmatolepis sigmoidalis, and Rhodalepis polylophodontiformis was recognized in Beds 113–115c. Beds 105–112 commonly contain Palmatolepis expansa, P. gracilis, and P. sigmoidalis. Bed 119 yielded a basal Carboniferous index conodont Siphonodella sulcata. In Beds 116–118, solenoporids such as Pseudochaetetes elliotti and Parachaetetes sp. were characteristic species in organic-carbon-rich dark gray limestone. Facies 1 is characterized by bioclastic, peloidal, and intraclastic grainstone and packstone containing massive normal grading and cross-laminations, and is interpreted to represent deep ramp carbonates above storm wave base. Facies 2 is represented by typical lag deposits overlying a transgressive surface. Facies 3 comprises organic-carbon-rich black shale and minor scour-filling bioclastic, peloidal, and intraclastic packstone, and may represent a marginal basin plain environment surrounding a carbonate ramp. The alternations of organic-carbon-rich black shale and dark gray packstone (Facies 3) show no evidence of bioturbation and have high TOC contents (0.18–5.73 wt.%). A minor succession within the transgressive lag deposits (from Bed 115b of Facies 2 to Beds 115c–120 in the lower part of Facies 3) is equivalent to the Hangenberg Black Shale (s. l.) in the middle part of the Siphonodella praesulcata to Siphonodella sulcata zones, because Beds 115b–120 characterized by no evidence of bioturbation and high TOC contents are interpreted to be accumulated in anoxic to dysoxic conditions.

article i nfo In the An Chau basin in northeastern Vietnam, the Olenekian (Lower Triassic) stage comprises mixed carbonate and siliciclastic shallow marine to marginal basin deposits that extend into the southern Nanpanjiang basin in South China. The upper Lang Son Formation, which is dominated by siliciclastic facies, is composed of storm- and wave-influenced shallow marine and slope deposits. The overlying and interfingering Bac Thuy Formation consists of tidal flat, wave-influenced carbonate platform, slope, and marginal basin plain deposits. The tidal flat deposits are composed mainly of lenticular, wavy-bedded, or thin flat-bedded carbonates containing desic- cation cracks and ripples that are indicative of bidirectional paleocurrents. The platform carbonates are charac- terized by wave ripples, ooids, and abundant marine mollusks and microfossils; the molluscan fossil assemblage primarily contains Smithian ammonoids such as Owenites koeneni. The slope deposits are character- ized by limestone breccia and slump beds. The marginal basin plain deposits consist of classical turbidite beds, minor limestone breccia, and hemipelagic mudstone and marl containing the Spathian ammonoids Tirolites and Columbites. The turbidite sets may represent frontal splay environments in the marginal basin plain. These Olenekian carbonate and siliciclastic facies are typical of a transgressive succession. The Smithian-Spathian boundary and the anoxic to dysoxic facies of the latest Smithian are characterized by organic-rich dark gray limestone and mudstone deposits intercalated in the succession of slope to marginal basin plain facies, which are composed mainly of gravity flow and hemipelagic deposits. The organic-rich deposits show no evidence of bioturbation and are characterized by low-diversity fauna. Clastics in the marginal basin plain deposits were apparently supplied from the west; hence, the paleocurrent direction of the siliciclastic gravity flows was approximately eastward.

Discovery of Sirenites senticosus (Dittmar) in the upper part of the Sabudani Formation of the Kurosegawa Belt, Kito area, Tokushima Prefecture, Japan, establishes a late Early Carnian age for this part of the stratigraphic unit. Because S. senticosus was mainly distributed in the Tethyan region, its occurrence provides evidence that Late Triassic ammonoids of Japan had strong affinities with those of the Tethyan faunas. This finding clearly differs from the biogeographic distribution of contemporary bivalves in the region, which are referred to as the Kochigatani bivalve faunas, and show strong affinities to faunas of the Boreal region.

Early Cretaceous bryozoans are key to understanding the evolutionary radiation of order Cheilostomata, the dominant modern group. Prior to the current study, there were few records of any Cretaceous cheilostomes from eastern Asia, and no pre-Cenomanian records. We found bryozoan fossils to be common in brackish-water to marine deposits representing estuary–tidal-flat and shoreface–inner-shelf habitats in the late Albian–early Cenomanian Goshoura Group, Goshoura Island, Kyushu, Japan. Bryozoans from the Goshoura Group were poorly preserved; for identification, we made silicone casts of colony moulds and studied them by scanning electron microscopy (SEM). We detected six cheilostome and one cyclostome species (Berenicea sp. 1), all forming multiserial encrusting colonies. We erect the new genus Haplostoechios for two new Conopeum-like malacostegans (H. hayamiae and H. clusum), and describe another new malacostegan as Charixa goshouraensis. Additionally, we briefly describe three species detected from a sing...

Well preserved molluscan fossils of Olenekian age (Early Triassic) were obtained from the upper part of the Bac Thuy Formation in Lang Son City, northern Vietnam. We report here an ammonoid, Xenoceltites variocostatus Brayard and Bucher, and describe two bivalve species, Crittendenia australasiatica (Krumbeck) and Crittendenia langsonensis sp. nov. Xenoceltites variocostatus is a characteristic species of the uppermost Smithian Anasibirites ammonoid zone and the earliest Spathian Tirolites ammonoid zone. Crittendenia austral- asiatica and C. langsonensis may thus be significant diagnostic species suggesting a middle Olenekian age. In addition, these occurrences demonstrate a probable faunal exchange between the eastern Tethys and eastern Panthalassa during the Olenekian, because many species of Crittendenia have been reported from Asia and from Panthalassic basins in the United States.

The mid-Cretaceous bivalve Goshoraia Tamura, 1977, endemic to Japan, is an early example of shallow-marine siphonate bivalves of the family Veneridae Rafinesque, 1815. Three species, including one new, are here described: Goshoraia minor Tashiro and Kozai, 1989 (Aptian), G. crenulata (Matsumoto, 1938; Albian–lower Cenomanian) and G. maedai sp. nov. (middle to ?upper Cenomanian). The habitats of Goshoraia have been extensively compared with those of common Cretaceous, nonsiphonate burrowers, such as trigoniids, which range from tidal flat and shoreface to shelf environments. Depth of burial, which can be estimated from the extent of the pallial sinus, increases from the ancestral G. minor to its descendants G. crenulata and G. maedai sp. nov., documenting that the ability to burrow within this genus improved in time. These morphological and palaeoecological changes may be related to the Mesozoic marine revolution during the mid-Cretaceous.