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To identify chronological changes in the marine reservoir effect in southwest Japan, the radiocarbon ages of eight pairs of marine shells and terrestrial plants were measured from the same horizons of one core of Holocene sediments. This core was obtained from the northern part of the Sukumo Plain in southwestern Shikoku Island, which faces the warm Kuroshio Current. The drilling site is located in an area of subsidence associated with the convergence of the Philippine Sea Plate and the Eurasian Plate. On analyses of lithology, molluscan assemblages, and radiocarbon dating, we interpreted, from oldest to youngest, nine units: basement rock, a braided river channel, a meandering river channel, an estuary, a transgressive inner bay, Kikai-Akahoya volcanic ash, a deltaic inner bay, a tidal flat, and artificial soil. Changes in the depositional environment were mainly associated with sea-level rise after the end of the last glaciation. The reservoir ages of the eight pairs, 330 ± 70 yr, were obtained from a transgressive inner bay to deltaic inner bay sediments, formed during 4100–9200 cal BP. The chronological change in the reservoir effect allows us to correlate the Sukumo Core sediments with previous results from southwestern Japan, the Korean Peninsula, and Taiwan Island.

To investigate the relationship between paleoenvironmental changes and marine reservoir effects, the radiocarbon ages of marine bioclasts and terrestrial plants from the same horizons of a sediment core in the Holocene Epoch were measured. This core, with a length of approximately 9 m, was obtained from the southern part of the Miyazaki Plain southeast of Kyushu Island, which faces the Kuroshio warm current. This drilling site is located in an uplift area associated with the subduction of the Philippine Sea Plate. Based on analyses of lithology, molluscan and foraminifera assemblages, and radiocarbon dating, we interpreted four sedimentary units in order of age: tidal flat, inner bay, Kikai-Akahoya volcanic ash, and delta plain. These paleoenvironmental changes were mainly associated with the sea-level rise during the deglacial period. The reservoir ages of nine pairs from the tidal flat to inner bay facies were found to be from the time span of 7300–8200 cal BP. The chronological changes in the reservoir effect are correlated with those seen in Holocene sediments of the other coastal area in East Asia.

An impact with a dash of volcanism Around the time of the end-Cretaceous mass extinction that wiped out dinosaurs, there was both a bolide impact and a large amount of volcanism. Hull et al. ran several temperature simulations based on different volcanic outgassing scenarios and compared them with temperature records across the extinction event. The best model fits to the data required most outgassing to occur before the impact. When combined with other lines of evidence, these models support an impact-driven extinction. However, volcanic gases may have played a role in shaping the rise of different species after the extinction event. Science , this issue p. 266

Deep-sea benthic ostracod assemblages covering the last 2 Myr were investigated in Integrated Ocean Drilling Program Site U1426 (at 903 m water depth) in the southern Sea of Japan. Results show that (1) orbital-scale faunal variability has been influenced by eustatic sea-level fluctuations and oxygen variability and (2) secular-scale faunal transitions are likely associated with the mid-Brunhes event (MBE, ~0.43 Ma) and the onset of the Tsushima Warm Current (TWC, ~1.7 Ma).Krithe,Robertsonites, andAcanthocythereisare the three most abundant genera throughout the core, accounting for 78.5% of total specimens. Multiple-regression tree analysis indicated that the TWC, the MBE, and oxygen content are the significant controlling factors of ostracod dominance. Changes in assemblages exhibit decline and recovery patterns corresponding to orbital-scale cyclicity of sea-level changes. In the Sea of Japan marginal ocean setting, this cyclicity shows a close relationship with bottom-water oxygen variability since the onset of the TWC influx. The MBE amplified the influence of the TWC and oxygen variability to the deep-sea ecosystem through larger sea-level fluctuations.Acanthocythereis dunelmensis, a circumpolar species, dominates before the TWC onset. After the TWC onset and during the mid-Pleistocene transition (MPT, ~1.2–0.7 Ma)Krithespp., known for their low-oxygen tolerance, substantially increase under moderate oxygen depletion. At the end of the MPT,Krithedominance diminishes and is replaced byRobertsonites hanaiiandPropontocyprisspp. after the MBE. The post-MBE assemblage, characterized byR. hanaii, suggests a slightly warmer environment under the development of the TWC. In addition, the post-MBE high-amplitude climate system may have caused the increased abundance of active-swimmingPropontocyprisspp. due to their superior migration ability. Benthic ecosystems in marginal seas are sensitive and vulnerable to both short- and long-term climatic changes, and the MBE is suggested to be a global biotic event affecting benthic ecosystems substantially.

The Sea of Japan (also termed the East Sea) has a circulation system isolated from the Pacific Ocean and East China Sea. The East Asian winter monsoon drives the circulation system and cools the Tsushima Warm Current (TWC) to form the Japan Sea Intermediate–Proper Water (JSIPW). The intermediate water conveys oxygen to deep-sea floors, which is available for benthic animals. During the Pliocene (3.5–2.8 Ma), Temperate Intermediate Water (TIW) was formed under the weak winter monsoon, and extinct ostracod TIW taxa were found. Little is known about early Pleistocene intermediate water and the extinction mode of benthic ostracods. We studied radiolarians and ostracods from deep-sea sediments between 2.0 and 1.3 Ma (Marine Oxygen Isotope Stage [MIS] 77 to MIS 41) at Integrated Ocean Drilling Program Site U1426, Sea of Japan. The ostracod faunas contained TIW and JSIPW taxa. The radiolarian subtropical-water taxa and the JSIPW ostracods indicate a small influx of the TWC and the JSIPW. The TIW occasionally expanded to the middle bathyal zone. By analogy with the relationship between the modern JSIPW and winter monsoon, weak winter monsoon possibly caused gentle temperature gradients in the water column and the expansion of the TIW. The JSIPW taxa expanded their ranges into the deep sea during interglacial periods.

During the Paleocene, the marine plankton community recovered its diversity after a severe diversity loss at the Cretaceous/Paleogene (K/Pg) boundary. In general, changes in Paleocene deep-sea ostracode faunas are poorly understood. It is still unclear how the deep-sea ostracode faunas changed during compelling events such as the K/Pg boundary (66.04 Ma) and the Latest Danian Event (LDE: ~ 62.18 Ma), a transient Paleocene warming event. In this report, we describe a study on the latest Cretaceous–Late Paleocene ostracodes from Integrated Ocean Drilling Program Site U1407, off Newfoundland, in the northwestern Atlantic. Thirty-six ostracode taxa were obtained from 202 discrete samples that were collected from the interval between 66.3 and 57.3 Ma. Near the K/Pg boundary, 8% (2 of 25) of the Maastrichtian taxa became extinct. The extinction rate is estimated to be at most 0.12 E MSY − 1 , which is equal to extinction rate of 12% per one million years and is in the same range as the background-level extinction rate. Comparing the extinction rates between different ocean basins such as Maud Rise and Blake Nose, the ostracode extinction at the K/Pg boundary displays striking geographical heterogeneity. Between the Maastrichtian and Danian, the ostracode faunas change from a biofacies dominated by shallow bathyal taxa to one dominated by deep bathyal taxa. During the LDE, ostracode faunas display an increase in their benthic ostracode accumulation rates and taxonomic diversity as well as an increase in the relative abundance of Krithe crassicaudata simultaneously with a decline in carbonate content. A similar change is commonly documented in fauna from the northeastern Atlantic during the Paleocene–Eocene Thermal Maximum (PETM; 56.0 Ma). In contrast to the PETM fauna, an extinction event is not recognized. Near the Danian/Selandian boundary, the ostracodes show an increase in export productivity. After the Danian, the ostracodes form a community that appears to tolerate warm and acidified water. Export productivity remains high during the Selandian and Thanetian.

Sexual dimorphism is thought to have evolved via selection on both sexes. Ostracodes display sexual shape dimorphism in adult valves; however, no previous studies have addressed temporal changes on evolutionary timescales or examined the relationships between sexual shape dimorphism and selection pressure and between sexual shape dimorphism and juvenile shape. Temporal changes in sexually dimorphic traits result from responses of these traits to selection pressure. Using the Gaussian mixture model for the height/length ratio, a valve-shape parameter, we identified sexual differences in the valve shape ofKrithe dolichodeiras.l. from deep-sea sediments of the Paleocene (62.6–57.6 Ma) and estimated the proportion of females in the fossil populations at 11 time intervals. Because the proportion of females in a population is altered by the mortality rate of adult males, it is reflective of selection pressure on males. We attempted to correlate the height/length ratios between the sexes with the proportion of females, taking into consideration that the valve shape was not linked with the selection pressure on males. In time-series data of the height/length ratio, both sexes indicate no significant changes on evolutionary timescales, even though the sex ratio of the population changed from female skewed to male skewed during the late Paleocene. The sexual shape dimorphism was not driven by sexual selection. The static allometry between the height/length ratio and length indicates that the sexual shape dimorphism did not function for sexual display. The absence of change over time in the female allometric slope suggests that the evolution of valve shape was constrained by stasis.

In ocean drilling sites, the taxonomy of Paleocene ostracodes has been poorly investigated. We describe and illustrate 18 ostracode taxa from Cretaceous—Paleocene sediments at U1407 of Integrated Ocean Drilling Program Expedition 342 off Newfoundland, Northwestern Atlantic; these 18 taxa belong to the families Cytherellidae, Bairdiidae, Pontocyprididae, Bythocytheridae, and Cytheruridae, and include five new species: Bythoceratina subumbonata sp. nov., Bythoceratina wilsoni sp. nov., Cytheropteron newfoundlandense sp. nov., Cytheropteron americanum sp. nov., and Nemoceratina (Pariceratina) guerneti sp. nov. Our identification and description of the taxa enable us to assess paleobiodiversity and paleoenvironments on the seafloor in the North Atlantic.

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.

A scanning electron microscope (SEM) is a very common instrument to observe fossil specimens. Although a low-vacuum SEM is now getting to be a common tool, still a conductive coating is required for observation of specimens at higher magnification. For SEM images of nonconductive fossil specimens, the specimens are usually coated with metals such as gold and platinum. The metal sputter coating method has a problem that the coating reduces the transparency of the fossil specimens when observed under a transmitted optical microscope. Therefore, the metal coating may not be suitable for observation of types in museum research collections. We applied an osmium plasma coating to the SEM preparation of microfossil specimens and found that the osmium coating neither shades transmitted light through the specimens nor masks the internal structures of the specimens. Also this method allowed us to observe specimens at high magnification. The osmium coating has an advantage over the metal sputter coating si...

Invertebrate fossils described from ancient hydrocarbon seep deposits represent diverse groups, e.g., brachiopods, mollusks, decapod crustaceans, worm tubes, and rare echinoderms, but the fossil record of ostracodes from hydrocarbon seep deposits is still very limited, making their ecology and evolutionary history still little known. We found fossil ostracodes in eight Eocene to Oligocene hydrocarbon seep deposits in the Humptulips, Lincoln Creek, Makah, and Pysht formations in western Washington State, USA. They represent eleven taxa belonging to genera found in a wide range of shelf to slope habitats: Acanthocythereis , Loxoconcha ?, Cytherella , Cytheropteron , Macropyxis ?, Krithe, Paracosta, Pontocythere ?, Propontocypris , Palmoconcha , and Neonesidea ? Acanthocythereis acroreticulata from one late Oligocene seep deposit in the Lincoln Creek Formation is the oldest and northernmost record for this species. The hydrocarbon seep ostracode faunas from Washington appear to be benthos-dominated, showing the same ecological structure and pattern of phylogenetic relatedness as ostracodes from Miocene and Quaternary seep sediments from Italy and off Ireland. We suggest that the benthos-dominated structure has been stable for ostracodes in hydrocarbon seep environments and/or has a higher preservation potential than the nektobenthos-dominated structure.

An assemblage of eleven species of Early Eocene marine intertidal and sublittoral ostracods has been found in the Crescent Formation in the Black Hills, Thurston County, Washington State, USA. The ostracods are subtropical and tropical taxa, such as Bairdoppilata, Cytherella and Neomonoceratina, which are found south of Washington today. Based on the geological age of the formation, the fauna corresponded to the Early Eocene Climatic Optimum. Five new species are recognized: Acanthocythereis olympiana sp. nov., Ambostracon irizukii sp. nov., Bairdoppilata crescentana sp. nov., Coquimba washingtonensis sp. nov. and Cytherelloidea squiresi sp. nov. This new assemblage from the Crescent Formation is the northernmost record of Early Eocene ostracods for the entire Pacific Basin.

Modern global change threatens alpine ecosystems by forcing species to migrate to higher elevations and potentially eliminating alpine habitat altogether. Here we show that an analogous restriction of suitable habitat operates on submarine mountains. During the Paleocene–Eocene Thermal Maximum (PETM, ca. 55.96 Ma), ostracodes underwent local extinction on the crest of Allison Guyot in the central Pacific Ocean, which lost 64% of its ostracode species richness (14 species reduced to three species) and as much as 94% of ostracode abundance for ∼1.1 m.y., before recolonization rebuilt biodiversity and abundance over the next 200 k.y. Biotic changes may reflect an increase in current speeds, acidification, and a decrease in food supply owing to a temperature-driven increase in metabolic rates. Notably, continental margin ostracodes also underwent extinction during the PETM (25%–38% loss) but, unlike Allison Guyot faunas, could quickly repopulate the continental slope. The absence of refugia for isolated seamounts prolonged the reduction in biodiversity initiated by the PETM, a pattern that may be expected for modern seamount faunas in an era of future global change.

The Eocene–Oligocene transition (EOT) is associated with a major eustatic sea-level fall, sea surface cooling, change in ocean stratification, and enhanced seasonality. While these changes are well known to have significantly restructured open ocean ecosystems, comparatively little is known about how these multiple environmental changes affected coastal biotas. Here we describe ostracode faunas in shelf deposits in the Gulf Coast of Mexico through the Late Eocene to Early Oligocene, analyzing the biostratigraphy and paleoecology of ostracodes from the Mossy Grove core, Mississippi. Mossy Grove ostracode faunas suffered gradual extinction and diversity loss in the 150 kyr between 33.96 and 33.81 Ma. During the turnover, 10 of 21 species disappeared. Seven of the 12 disappearing species became extinct, while others are Lazarus taxa that later re-appeared in the Vicksburgian (~ 33.7 Ma). During the sea-level fall associated with the Eocene/Oligocene (E/O) boundary (33.90 Ma), six of seven outer-shelf taxa disappeared, while three of four inner-shelf taxa increased in abundance. The major changes in ostracode assemblages occur during the EOT-1 and EOT-2 events prior to the Oi1 isotope excursion and appear to reflect a combination of impacts from eustatic sea-level fall and local enhanced surface ocean seasonality shown in stable isotope records from the St Stephen's Quarry core, Alabama.

The Paleocene–Eocene Thermal Maximum (PETM) has been held up as a past analog to future environmental change and presents the opportunity to study climate impacts on marine communities. During the PETM, deep-sea benthic foraminifers decreased their body-size and increased their productivity, metabolic rates, and food consumption in response to abruptly increasing temperature and changing surface water productivity. Here we find that three species of marine ostracodes – part of the multicellular benthos – also experienced a reduction in body-size in response to PETM warming in the Northeast Atlantic. Positive correlations between ostracode body-size and benthic foraminiferal oxygen isotope data indicate that reduced body-sizes were caused by high temperature during the PETM. Dwarfing of ostracodes during the PETM interval suggests that their food consumption rates, and lifetimes, were less than those of ostracodes in the pre-PETM interval. This interpretation is based upon previous studies that show that food consumption and ostracode lifetimes both decrease as ostracodes increase their growth rates under higher temperatures. Estimates of body volume, temperature, and individual abundance suggest a decline in lifetime metabolic rate in ostracode individuals during the core of the PETM. In addition there is also a decrease in biomass flux in the whole ostracode community at this time. The decline in biomass flux at the community level suggests major changes in the energy flow and carbon cycling in deep-sea benthic ecosystem and the reduction of organic carbon flux between the ostracode community and sediments during the PETM. The decline in ostracode carbon flux stands in contrast with previous interpretations that carbon cycling by benthic foraminifera increased during the PETM. Hence, our data suggest that the benthic community response to the PETM was not uniform between different taxonomic groups.

The Indo-West Pacific (IWP) benthos, which shows the highest diversity of marine organisms worldwide, is thought to have originated from the Tethys Ocean. Little is known about Miocene ostracodes in the IWP, that is, subsequent to the closure of the Tethys Ocean. To understand the paleobiogeography of Miocene ostracodes in the IWP, we examined ostracodes from the Middle Miocene—Lower Pliocene Osaki Formation, Kukinaga Group, at Tanegashima, Southwest Japan, revealing the presence of Neocytheromorpha, an IWP taxon that originated from South Australia. Neocytheromorpha occurs abundantly with Trachyleberis in Middle Miocene sublittoral deposits. This finding indicates that Neocytheromorpha migrated northward from South Australia, along the Australian coast, and settled in coastal areas of the West Pacific during the Oligocene—Middle Miocene. Because the migration coincided with diversification in the West Pacific and the invasion of corals and molluscs, it was synchronous with changes in the popula...

Previous low resolution studies suggest that ostracodes, in contrast with deep sea foraminifera, largely survived the massive environmental changes of the Paleocene–Eocene thermal maximum (PETM). In a new high-resolution study from the continental slope (~ 1800 m paleodepth) NE Atlantic, we also find extensive survivorship of ostracode faunas, but this is accompanied by a temporary drop in species diversity and ecological diversity during the PETM. There are 12 common ostracode species before the PETM that are reduced to only two species at the same time as the benthic foraminiferal extinction event. All but three species reappear in the later parts of the PETM and statistical analysis suggests that most of the apparent “Lazarus” species might be found with sufficient sampling of PETM faunas. We find no evidence for an excursion fauna of ostracodes as has been detected in calcareous nannofossils, planktic foraminifera, and benthic foraminifera. However, the ostracode assemblages changed from a relatively diverse ecological assemblage before and after the PETM to one dominated by infaunal species typical of low oxygen conditions during the PETM. The absence of major extinction and the temporary nature of species disappearances are comparable to turnovers in shallow marine ostracodes and stands in sharp contrast to the ~ 50% species-level extinction in benthic foraminifers.

Cythere ikeyanoriyukiin. sp., an extant phytal ostracode genus, was obtained from the Middle Eocene McIntosh Formation in the Doty Hills, western Washington State, USA. It was associated with eleven taxa, which are extant phytal and shelfal genera such asLoxocorniculum,Xestoleberis,Ambostracon,Coquimba, andAcanthocythereis.The presence ofCytherein this assemblage is surprising and indicates that the first appearance of this genus was middle Eocene time at the latest, or at least 20 Ma earlier than previously thought.Cytheredid not originate in the Pacific Ocean around Japan as previously thought, but instead must have migrated from the northeastern Pacific to the northwestern Pacific between middle Eocene and early Miocene time.

Cythere ikeyanoriyukii n. sp., an extant phytal ostracode genus, was obtained from the Middle Eocene McIntosh Formation in the Doty Hills, western Washington State, USA. It was associated with eleven taxa, which are extant phytal and shelfal genera such as Loxocorniculum, Xestoleberis, Ambostracon, Coquimba, and Acanthocythereis. The presence of Cythere in this assemblage is surprising and indicates that the first appearance of this genus was middle Eocene time at the latest, or at least 20 Ma earlier than previously thought. Cythere did not originate in the Pacific Ocean around Japan as previously thought, but instead must have migrated from the northeastern Pacific to the northwestern Pacific between middle Eocene and early Miocene time.

During the Eocene, Hahajima Island of the Ogasawara (Bonin) Islands of the Izu-Mariana Arc in the North Pacific was located near the present-day position of western Pacific Micronesia. We identified 17 Eocene ostracode species from the island, of which are new species and likely endemic to this island or to the West Pacific. These new species are systematically described herein and include:Costa matsumaruin. sp.,Cytherelloidea ogasawaraensisn. sp.,Havanardia ujiiein. sp.,Jugosocythereis nishiin. sp.,Neonesidea boninensisn. sp.,Schizocythere antiquimicronesianan. sp., andUroleberis hahajimaensisn. sp. The Eocene ostracode fauna has a higher rate of endemism than does the modern Micronesian fauna and contains Tethyan genera. These findings contradict a hypothesis that the Pacific fauna had a higher endemism rate after the Paleogene. The findings support another hypothesis that some genera invaded the Pacific from Tethys during the Paleogene. They suggest that West Pacific species did not disperse to the periphery of the Indo-West Pacific region during the Middle–Late Eocene. The “center of origin” hypothesis cannot be applied to Middle–Late Eocene marine ostracode biogeography.

We report on Eocene ostracode species from Hokkaido, northern Japan for the first time and discuss their paleobiogeographic implications. Five species were found in the lower part of the Sankebetsu Formation in the Haboro area, and the Akabira and Ashibetsu Formations in the Yubari area, central Hokkaido. The ostracode assemblages are characterized by Robertsonites, a circumpolar Arctic genus of the modern fauna. This finding marks the southernmost occurrence of the Eocene record of the genus, as well as the oldest occurrence. As the characteristics of the Eocene Hokkaido fauna are similar to those of the modern-day fauna in the Seto Inland Sea, a contrast in species composition is observed between the Seto Inland Sea and Kyushu. This contrast is attributable to differences in sea temperature. Five species are described, including Robertsonites ashibetsuensis sp. nov.

Six ostracode species were discriminated from the latest Eocene-earliest Oligocene marine sediments in Kurashiki City, Okayama Prefecture along the Seto Inland Sea in southwestern Japan. The ostracode assemblage is characterized by Munseyella setouchiensis and Acanthocythereis kurashikiensis sp. nov. They inhabited the lower sublittoral zone, affected by ocean waters. The new record from the Kurashiki area indicates that the eastern area of the Seto Inland Sea was under a cooler marine climate than the Kyushu region from the late Middle Eocene to earliest Oligocene. All the species including a new species, Acanthocythereis kurashikiensis sp. nov., are described systematically.

The Paleogene Iojima Group is exposed in the Takashima coalfield of northwestern Kyushu, southwest Japan. The group is divided into four formations: the Okinoshima, Magome, Funazu, and Daimyoji formations (in ascending stratigraphic order). Among these strata, mudstone and muddy sandstone of the Okinoshima and Funazu formations contain a number of common age-diagnostic calcareous microfossils, nannofossils, and planktic foraminifers. Our biostratigraphic study of the Paleogene Iojima Group indicates that the Okinoshima Formation corresponds to calcareous nannofossil Zone CP14 and planktic foraminiferal Zones E10-E13; the Funazu Formation is assigned to Zones CP14-CP16. The Okinoshima and Funazu formations are assigned to the late middle Eocene and late middle Eocene to early Oligocene, respectively, suggesting that 1) the Okinoshiman molluscan Stage correlates with the middle Eocene, as proposed in previous studies; and 2) the Magome Formation, which includes coal-bearing strata, correlates with ...

Middle Eocene–early Oligocene ostracode faunal changes in northwestern Kyushu of southwestern Japan are identified in this study. Ostracodes occur from shelf deposits of five formations: the middle Eocene Okinoshima, the upper Eocene Funazu, the uppermost Eocene–lowermost Oligocene Kishima, the lowermost Oligocene Itanoura, and the lower Oligocene Waita Formations. The middle Eocene–earliest Oligocene ostracodes were characterized by warm-water genera, indicating tropical, subtropical and Tethyan genera, whereas the late early Oligocene ostracodes do not include warm-water taxa, consisting of temperate realm genera. The middle Eocene–earliest Oligocene ostracodes do not include remarkable changes of species composition, in contract with equatorial Pacific radiolarians and West Coast USA molluscs. Ostracodes suggest that distinct climatic cooling did not occur in the southwestern Japan during the middle Eocene–earliest Oligocene.

The genus Palmoconcha in the family Loxoconchidae of Ostracoda is found in Cenozoic sediments from the North Pacific. The genus Palmoconcha from the North Pacific is divided into two morphological groups: One is the P. parapontica characterized by having a prominent murus along a posterodorsal margin. Another is the P. laevimarginata group characterized by the nonprominent murus. Both the P. parapontica and P. laevimarginata groups contain six species including a new species and six species, respectively. The P. parapontica group is distributed in only northwestern Pacific, whereas the P. laevimarginata group occurs in both the western and eastern sides of the North Pacific. The assemblages occupied by the P. parapontica group, together with Acanthocythereis, Falsobuntonia, and Robertsonites occur from deposits of Japan during the middle Miocene and the early Oligocene climatic cooling. They associate with temperate molluscan faunas, and are considered to have appeared in shelf environments under...

The ostracode genus Bicornucythere (Ostracoda, Crustacea) is abundant in modern-day eutrophic marine bays, and is widely distributed in estuaries and inner bays throughout East Asia, including in China, Korea, Japan, and the Russian Far East. The evolutionary history of Bicornucythere is poorly understood. Here, we report on a new species of Bicornucythere (Bicornucythere concentrica sp. nov.) from the upper Eocene Yaw Formation in the Central Myanmar Basin. The oldest previously known Bicornucythere taxon, Bicornucythere secedens, was reported from lower Miocene strata in India, although a molecular phylogeny suggests that the genus first appeared in the Late Cretaceous. Bicornucythere concentrica sp. nov. is at least 10.9 million years older than the earliest known B. secedens. The new species occurs with Ammonia subgranulosa, a benthic foraminifer, an association that is representative of brackish water conditions in modern Asian bays. Our findings indicate that extant genera have inhabited Asian bays since the late Eocene. The paleobiogeography of Bicornucythere indicates that the taxon was dispersed onto Indian coasts during the collision between the Indian and Eurasian plates.

Eocene ostracodes are described from the Japanese Islands for the first time. These ostracodes, from the Iojima Group in southwestern Japan, are represented by cosmopolitan and low- to midlatitudinal paleobiogeographic groups as well as an endemic group. Based on the distributions of selected genera, the ostracode fauna of the Iojima Group has tropical to subtropical affinities, affirming links with the Tethys Sea. Six species are described as new: Cytheropteron liue, Eopaijenborchella kamiyai, Eopaijenborchella okinoshimaensis, Ambtonia? matsubarai, Paracypris? kuritai, and Trachyleberis? funatsuensis.

The ostracode fauna from the middle–upper Eocene Iwaya Formation on Awajishima Island, Hyogo Prefecture, southwestern Japan was studied to reveal a band of the Eocene ostracode faunal spectrum in the middle latitudes of the northwestern Pacific. Based on lithofacies and previously reported calcareous nannofossils, molluscs, and benthic foraminifers, the ostracodes were found to have inhabited inner shelf environments. The ostracodes entirely differ from the Eocene–earliest Oligocene faunas in Kyushu, southwestern Japan and the East China Sea, both in generic and specific composition. The difference is considered to be due to paleoclimatic and paleogeographic differences between Awajishima Island and more southern latitudes at that time. Described species include three new species, Munseyella setouchiensis sp. nov., Hanaiborchella reticularitriangularis sp. nov., and Trachyleberis awajiensis sp. nov.

At least thirty-three ostracode species are reported for the first time from the Oligocene Itanoura Formation, Nishisonogi Group. This is also the first report of Oligocene ostracodes from the Japanese Islands. Fifteen samples bearing fossil ostracodes were grouped into three biofacies (A to C). Three biofacies have characteristics as follows: Biofacies A is dominated by Acanthocythereis volubilis (Liu) and Eopaijenborchella sinensis (Liu); Biofacies B is dominated by Krithe sp. associated with Palmoconcha oujiangensis (Liu) and A. volubilis; Biofacies C dominantly includes P. oujiangensis. The lithofacies, fossil molluscan assemblages and planktonic/total foraminifers ratios suggest the following habitats for the ostracodes: all ostracode species from the formation inhabited a shelf influenced by coastal water; dominant species of Biofacies A flourished in environments shallower than those of Biofacies B. Fossil ostracode assemblages from the Itanoura Formation have lower numbers of species and ...

Integrated Ocean Drilling Program Expedition 342 was designed to recover Paleogene sedimentary sequences with unusually high deposition rates across a wide range of water depths (Sites U1403–U1411). The drilling area is positioned to capture sedimentary and geochemical records of ocean chemistry and overturning circulation beneath the flow of the Deep Western Boundary Current in the northwest Atlantic Ocean. In addition, two operational days were dedicated to a sea trial of the Motion Decoupled Hydraulic Delivery System developmental tool (Site U1402). The expedition was primarily targeted at reconstructing the Paleogene carbonate compensation depth (CCD) in the North Atlantic for reference to recently obtained high-fidelity records of the CCD in the equatorial Pacific. The site located in the deepest water (Site U1403) was at a paleodepth of ~4.5 km 50 m.y. ago, whereas the site located in the shallowest water (Site U1408) can be backtracked to a paleodepth of 2.5km at the same time. The combination of sites yields a record of the history of CCD change over a 2km depth range from the ocean abyss to middle range water depths. Notable findings include the discovery of intermittent calcareous sediments in the Cretaceous, Paleocene, and early to middle Eocene at 4.5 km paleodepth, suggesting a deep Atlantic CCD during these times. We find evidence of carbonate deposition events following the Cretaceous/Paleogene (K/Pg) boundary mass extinction, the Paleocene/Eocene Thermal Maximum, and the Eocene–Oligocene transition. These deposition events may reflect the rebalancing of ocean alkalinity after mass extinctions or abrupt global climate change. Intervals during which the CCD appears to have been markedly shallow in the North Atlantic include the Early Eocene Climatic Optimum, the late Eocene, and the middle Oligocene. A second major objective of Expedition 342 was to recover clay-rich sequences with well-preserved microfossils and high rates of accumulation in comparison to the modest rates of accumulation (~0.5–1 cm/k.y. in the Paleogene) typically encountered at pelagic sites. As anticipated, Expedition 342 recovered sequences with sedimentation rates of as much as 10 cm/k.y.—high enough to enable studies of the dynamics of past abrupt climate change, including both transitions into “greenhouse” and “icehouse” climate states, the full magnitudes of hyperthermal events, and rates of change in the CCD. We find that the thickest central parts of the various sediment drifts typically record similar depositional packages to those recovered in the thin “noses” and “tails” of these drifts, but these central parts are often massively expanded with clay, especially near the CCD. Times of rapid accumulation of drift deposits include the early Eocene to late middle Eocene, the late Eocene to early Oligocene, the late Oligocene and early Miocene, the later Miocene to probable late Pliocene, and the Pleistocene. Widespread hiatuses are present near the Paleocene/Eocene boundary into the middle early Eocene and the middle Oligocene. The Eocene/Oligocene boundary is a period of slow sedimentation at most sites but is expanded at Site U1411. A marked change in the geometry of drift formation is observed in the ?late Pliocene, as has been observed in drift deposits elsewhere.

The ostracode genus Bicornucythere (Ostracoda, Crustacea) is abundant in modern-day eutrophic marine bays, and is widely distributed in estuaries and inner bays throughout East Asia, including in China, Korea, Japan, and the Russian Far East. The evolutionary history of Bicornucythere is poorly understood. Here, we report on a new species of Bicornucythere (Bicornucythere concentrica sp. nov.) from the upper Eocene Yaw Formation in the Central Myanmar Basin. The oldest previously known Bicornucythere taxon, Bicornucythere secedens, was reported from lower Miocene strata in India, although a molecular phylogeny suggests that the genus first appeared in the Late Cretaceous. Bicornucythere concentrica sp. nov. is at least 10.9 million years older than the earliest known B. secedens. The new species occurs with Ammonia subgranulosa, a benthic foraminifer, an association that is representative of brackish water conditions in modern Asian bays. Our findings indicate that extant genera have inhabited Asian bays since the late Eocene. The paleobiogeography of Bicornucythere indicates that the taxon was dispersed onto Indian coasts during the collision between the Indian and Eurasian plates.

The following caption was omitted from Appendix 2. The existing caption should be replaced with: Appendix 2 —Comparison of the length, height, and height/length ratio of left and right valves between Cythere ikeyanoriyukii n. sp. and eight described Cythere species, using the Dunnett post-hoc …

47才女子の両側性手根管症候群を伴つた全身性進行性硬化症(以下PSSと略)の1例を報告した。患者は臨床的, 組織学的に, PSSおよびSjogren症候群と確認され, 理学所見上, 手根管症候群と診断した。手根管にステロイドの局注を施行したが, 両手指の正中神経領域の疼痛, 痺れは改善されず無効であつたので, 両側横手根管靱帯縦切術を施行し自他覚症状の著明な軽快をみた。肥厚した横手根幹靱帯は, 組織学的に膠原線維の増生がみられ, PSSによる変化と思われた。