Ostracod Species Research Articles

Temporal constraints on the terrestrial biota from the Yingzuilazi Formation (Baishan Basin), northeast China

The biota from the Yingzuilazi Formation in the Baishan Basin yields a diverse fossil assemblage (including a new described ostracod species Cypridea horni sp. nov. Wang), which provides a valuable opportunity to investigate the evolution of major terrestrial plants and animals. However, the age of this biota is still controversial. To address this, we report a new SIMS zircon U–Pb age of 128.5 ± 1.0 Ma for the uppermost part of the Yingzuilazi Formation. This age, combined with our new ostracod biostratigraphic age from the Yingzuilazi Formation, indicate that the age of biota from the Yingzuilazi Formation is mainly Barremian (∼129 Ma to ∼127 Ma). It seems that the biota from the Yingzuilazi Formation temporal coincides with Jehol Biota sensu stricto stage I, but it is closely related to Jehol Biota sensu stricto stage II in terms of comprehensive biostratigraphic and paleontoloical materials. Therefore, this biota shows the significances not only in understanding the spatiotemporal evolution of the Early Cretaceous terrestrial biotas in East Asia, but also in exploring the possible relationship between the terrestrial life evolution and the destruction processes of the North China Craton.

High‐resolution environmental changes recorded in ostracod and mollusc fauna from the Holsteinian palaeolake at Ortel Królewski II, eastern Poland

To better understand the environmental variability during the Holsteinian interglacial, fauna of the palaeolake deposits at Ortel Królewski II, eastern Poland was investigated. The analysis covered the uppermost part of the profile, representing the so‐called pre‐optimal part of the Holsteinian interglacial (MIS 11c), namely the Taxus and Pinus‐Larix pollen zones. Variability within the structure and composition of the faunal assemblage enabled a high‐resolution palaeoecological reconstruction – lake level and temperature fluctuations, its trophy and energy of the environment. During the Taxus pollen zone the lake was relatively deep and characterized by medium trophy conditions, which is indicated by a low abundance of molluscs of temporary water bodies and low numbers of Metacypris cordata and Scottia tumida. The temperature was rather stable with only small fluctuations during the transition between the Taxus and Pinus‐Larix zones. The occurrence of some cold‐loving ostracod species within the beginning of the Pinus‐Larix pollen zone indicates some deterioration of thermal conditions, which was additionally confirmed by using the mutual ostracod temperature range (MOTR) method. Lake level drop and expansion of reed zones within the Pinus‐Larix pollen zone are inferred from the increased abundance of shallow water ostracod and mollusc species as well as from an increased Bithynia‐index (BIN). The short cooling event documented early in the Pinus‐Larix zone in the studied profile might be an equivalent to the mid‐MIS 11c cooling, the so‐called Older Holsteinian Oscillation. Thus, the improved knowledge about the climate dynamics recorded within the sediments from this site contributes to a better understanding of the spatial extent and pattern of the climatic changes within the Holsteinian interglacial across Europe.

Two new species of non-marine Ostracoda (Crustacea) of the genera Vestalenula Rossetti amp; Martens, 1998 (Darwinuloidea) and Microloxoconcha Hartmann, 1954 (Cytheroidea) from Tsushima, Japan, and a summary of the non-marine ostracod fauna of the island.

The archipelago of Tsushima is located in the Korea Strait, at the southern end of the Sea of Japan (East Sea), and lies almost equidistant from Korea and Japan. Its non-marine ostracod fauna was previously unknown, although potentially of (palaeo-) zoogeographical interest considering its position. Preliminary surveys of freshwater and brackish habitats on the island in August/September and November/December 2019, revealed a total of 31 species in five families and three superfamilies. Two species are described as new. Vestalenula gravata sp. nov. is a small representative of the family Darwinulidae, characterized by a very long keel on the right valve and the absence of a pigmented eye. This species was found in very shallow streams with poorly sorted substrates in forests. Microloxoconcha semicircularis sp. nov., an interstitial Cytheroidea, was recovered from the tidal part of a small river, the first time this genus has been found in this type of habitat. Two other undescribed species are figured, but left in open nomenclature due to insufficient number of individuals: Vestalenula sp. and Cobanocythere sp. The antennule and antenna of Vestalenula sp. are most similar to those of three species from Brazil.

A modern snapshot of the isotopic composition of lacustrine biogenic carbonates – records of seasonal water temperature variability

Abstract. Carbonate shells and encrustations from lacustrine organisms provide proxy records of past environmental and climatic changes. The carbon isotopic composition (δ13C) of such carbonates depends on the δ13C of dissolved inorganic carbon (DIC). Their oxygen isotopic composition (δ18O) is controlled by the δ18O of the lake water and by water temperature during carbonate precipitation. Lake water δ18O, in turn, reflects the δ18O of atmospheric precipitation in the catchment area, water residence time and mixing, and evaporation. A paleoclimatic interpretation of carbonate isotope records requires a site-specific calibration based on an understanding of these local conditions. For this study, samples of different biogenic carbonate components and water were collected in the littoral zone of Lake Locknesjön, central Sweden (62.99∘ N, 14.85∘ E, 328 ma.s.l.) along a water depth gradient from 1 to 8 m. Carbonate samples of living organisms and subfossil remains in surface sediments were taken from the calcifying alga Chara hispida, from bivalve mollusks of the genus Pisidium, and from adult and juvenile instars of two ostracod species, Candona candida and Candona neglecta. Our results show that neither the isotopic composition of carbonates nor the δ18O of water vary significantly with water depth, indicating a well-mixed epilimnion. The mean δ13C of Chara hispida encrustations is 4 ‰ higher than the other carbonates. This is due to fractionation related to photosynthesis, which preferentially incorporates 12C into the organic matter and increases the δ13C of the encrustations. A small effect of photosynthetic 13C enrichment in DIC is seen in contemporaneously formed valves of juvenile ostracods. The largest differences in the mean carbonate δ18O between species are caused by vital offsets, i.e., the species-specific deviations from the δ18O of inorganic carbonate which would have been precipitated in isotopic equilibrium with the water. After subtraction of these offsets, the remaining differences in the mean carbonate δ18O between species can mainly be attributed to seasonal water temperature changes. The lowest δ18O values are observed in Chara hispida encrustations, which form during the summer months when photosynthesis is most intense. Adult ostracods, which calcify their valves during the cold season, display the highest δ18O values. The seasonal and interannual variability in lake water δ18O is small (∼ 0.5 ‰) due to the long water residence time in the lake. Seasonal changes in the temperature-dependent fractionation are therefore the dominant cause of carbonate δ18O differences between species when vital offsets are corrected. Temperature reconstructions based on paleotemperature equations for equilibrium carbonate precipitation using the mean δ18O of each species and the mean δ18O of lake water are well in agreement with the observed seasonal water temperature range. The high carbonate δ18O variability of samples within a species, on the other hand, leads to a large scatter in the reconstructed temperatures based on individual samples. This implies that care must be taken to obtain a representative sample size for paleotemperature reconstructions.

Distribution pattern of different phenotypes of Limnocythere inopinata (an ostracod) from lakes in the Badain Jaran Desert, northern China

Limnocythere inopinata (Baird, 1843) is a widely distributed ostracod in modern non-marine waters and Quaternary sediments. Based on its morphological variation (the number and position of its nodes), different phenotypes have been identified. However, the factors controlling its morphological variation are currently open to debate, which hinders palaeoecological reconstructions based on this species. In this study, ostracod distribution and hydrochemical analyses of the ambient environment of 21 lakes in the Badain Jaran Desert were carried out. Three ostracod species belonging to two genera are identified as Limnocyhtere inopinata, Cypris cf. granulate and Cypris sp. with the dominant species L. inopinata represented by six phenotypes. The distribution features of these ostracods in the lakes and related ecological information are reported. In addition, the factors controlling the morphological variations of L. inopinata were analysed. Our data indicate that the noded individuals of L. inopinata prefer water with appropriate Ca2+ content (30–40 mg L−1) and low salinities (below 4.60 g L−1). The percentage of noded individuals of L. inopinata increases with increasing salinity only within a certain salinity range. Hence, caution should be exercised in reconstructions of palaeosalinity based on the morphological variability of L. inopinata.

Early Cretaceous non-marine ostracods from the Recôncavo Basin, Northeast of Brazil

The Early Cretaceous chronostratigraphic positioning of the northeast Brazilian basins is mainly based on ostracod distribution, including a biozoning proposal of local stages. The ostracod species were recovered from shales and siltstones samples along Gameleira, Manguinhos and Praia da Falha outcrops of the Maracangalha Formation (Recôncavo Basin). In the analyzed samples, six genera were recognized, out of a total of 1036 specimens. The non-marine ostracod fauna consists of the species Cypridea lunula Krömmelbein, 1962, Cypridea ellipsoidea Krömmelbein and Weber, 1971, Cypridea aff. C. vulgaris Krömmelbein, 1962, Cypridea sp. 1, Cypridea sp. 2, Cypridea sp. 3, Cypridea spp., Reconcavona? polita Viana, 1966, Reconcavona sp., Ilhasina amphotera Krömmelbein, 1963, Ilhasina sp. aff. I. remanei cuneiformis Krömmelbein, 1963, Ilhasina sp., Candona? condensa Krömmelbein, 1962, Brasacypris sp. and Alicenula sp. The biochronostratigraphic position of the Manguinhos outcrop in the Rio da Serra Stage (Berriasian–Valanginian) was possible through the identification of the guide species Reconcavona? polita, index in subzone RT-004.2. In the Praia da Falha outcrop the faunal association suggests an age range between the late Rio da Serra to Aratu Stage (Valanginian-Hauterivian), through the recording of the species Ilhasina amphotera and Cypridea lunula.

Ostracod assemblages from the Golubaya (Rybatskaya) Bay area on the outer northeastern Black Sea shelf over the last 300 years

A multi-proxy study of core Ash-2012-02 from the outer shelf of the northeastern Black Sea allowed us to define recent environmental changes, on a seven-year period resolution for the last 300 years. The age model of the core Ash-2012-02 based on radionuclide (210 Pb, 137 Cs, 241 Am) measurements suggests an average sedimentation rate of 1.4 mm/y and, consequently, a sedimentary record from end of the Little Ice Age to present. We subdivided the core section into five intervals mainly based on changes in relationships between ostracod species and their total abundance. Besides, the modern ostracod distribution on the northeastern Black Sea shelf was studied. Six main habitats with a specific ostracod species composition and environmental conditions have been investigated, as well as information on the temperature and salinity preferences for some ostracod species was provided. The ostracod species composition of assemblages remained similar throughout the core, but there were significant variations in the main ostracod species and the foraminiferal abundance. The hydrodynamic variations caused by climatic changes in the region are responsible for oxygen content in the bottom waters and affect the structure of the faunal assemblages. During the second half of the 20th century, an increasing trend of TOC and CaCO3 as well as considerable reduction in the ostracod diversity and the ostracod and foraminifera abundance are recorded in the muddy habitats, likely associated with unfavorable oxygen conditions and increased anthropogenic pressure.

Biodiversity of Non-Marine Ostracoda (Crustacea) of Botswana: An Annotated Checklist with Notes on Distribution

Botswana constitutes a major gap in our knowledge of the distribution of Ostracoda in the region of Southern Africa, restraining thorough biogeographic interpretations. We combine records from previously published surveys along with our own field collections to provide a collation of living and fossil (Late Pleistocene to Holocene) Ostracoda recorded in Botswana. Our survey yielded 17 species, of which nine species have not been recorded before in the country. Including the present update, 54 species (45 living and nine fossil or subfossil) belonging to 22 genera of five families (with 76% species belonging to the family Cyprididae) are currently reported from Botswana. Yet, 23 taxa are left in open nomenclature, indicating the urgent need for sound systematic studies on harmonizing taxonomy of Southern African ostracods, especially of those inhabiting small temporary waterbodies, considered as threatened with extinction before being properly described or discovered. This updated checklist provides detailed information about the distribution and habitat of each recorded species. Species richness, distribution patterns, and diversity of ostracod species regionally and in different freshwater ecoregions are also discussed. We found low alpha (site) diversity (mean 3.3 species per site) and a significant difference in species composition and beta diversity of the Okavango ecoregion versus the Kalahari and Zambezian Lowveld ecoregions.

Three new species of non-marine ostracods (Crustacea, Ostracoda) from small water bodies of northern China.

Three new species, Pseudocandonacheni sp. nov., Cyclocyprispangi sp. nov., and Tonnacyprisrectangularis sp. nov., collected from northern China, are described in this study. Pseudocandonacheni, of the compressa group, is difficult to be distinguished from other members of the same group by carapace morphology alone, but can be readily recognised by the structure of the hemipenis comprised of a long lobe a, distally inflated lobe h, and exteriorly pointed lobe b, as well as thick trunks of the male fifth limb endopodites. Cyclocyprispangi, despite its similarity in carapace morphology to its congeners, can be identified based on the morphology of the hemipenis, which bears a slender, slightly curved lobe h, and an S-shaped process accompanying lobe b, in addition to the rectangular trunk of the male fifth limb endopodite. On the other hand, Tonnacyprisrectangularis, described on the basis of females only, can be distinguished from other Tonnacypris Diebel & Pietrzeniuk, 1975 representatives by its distinct sub-rectangular carapace alone. Other differences include the length of the swimming setae, the length of the distal claws on the second antennae, and the morphology of the pincer organ on the seventh limb. This study contributes to the poorly known extant non-marine ostracod fauna of Inner Mongolia and Beijing, and generally to the central-eastern Palaearctic region. In addition, the known distribution range of Tonnacypris is extended eastwardly by T.rectangularis. The valve-morphology data are useful for identifying fossil/sub-fossil representatives.

Taxonomy and distribution of deep benthos collected in and around the Southern Ocean during the 30th Anniversary expeditions of R/V Hakuho Maru: Annelida, Mollusca, Ostracoda, Decapoda, and Echinodermata

The Southern Ocean is widely recognized for its unique benthic ecosystems, but benthic sampling has been largely restricted to shallower continental zones and much remains to be learned about the biodiversity in the bathyal and abyssal zones. In this study, we collected and investigated the deep-sea benthic habitat using geological dredges, a multiple corer, and a bait trap on-board the R/V Hakuho Maru in bathyal to abyssal depths between the latitude of 39°38.16′S–66°36.03′S and the longitude of 62°19.55′W–67°37.95′E in the Southern Ocean and the surrounding subantarctic region, focusing on West Antarctica. We carried out 20 geological dredges, 14 multiple corers, and a bait trap survey. Here, we present the taxonomic and distributional records of 180 species of Annelida, Mollusca, Ostracoda, Decapoda, and Echinodermata identified from our samples, including species-level identifications and detailed occurrence information where possible. Although West Antarctica is a highly investigated area for benthic biodiversity around Antarctica, our collection includes the annelid Flabelligena hakuhoae Jimi et al. 2020 which was new to science at the time of collection, and other potentially undescribed species of Annelida, Ostracoda, Asteroidea, and Holothuroidea. Several specimens collected updated the distribution ranges of their species.

Systematic and ecological study of recent Ostracoda from Al-Faw town, south of Iraq

Three boreholes were taken from Al-Faw town, Basrah, South Iraq; at a depth of about 29m, from an area in the flood plain of Shatt Al-Arab River. The cores were constituted essentially of silty clay and clayey silt which predominates the recent sediments. They are characterized by gray dark thin layer of silty clay between 16-17 m. The results indicated the disappearance of fossils in this thin layer due to the absence of water circulation. Twenty-six species of Ostracoda were identified, twelve taxa were recorded for the first time in the study area, these are Macrocyprina decora, Candona magnacauda, Cytherelloidea pracipua, Aurila cf. sp., Loxoconcha certinata, Loxocorniculum cf. sp., L. lilljeborg, Stigymatocythere indica, Neocytheromorpha reticulata, Cypridopsis sp., Cyprideis sp., Hemicytheridea sp., Krith sp. as well as three eco-facies: Fresh water, brackish water and shallow marine Ostracoda.

A Permian mixohaline ostracod association of the Teresina Formation, Paraná Basin, Brazil

New ostracod species are described for Middle to Upper Permian (Guadalupian) rocks of the Teresina Formation, Paraná Basin, from two localities in the São Paulo State, southwestern Brazil: Xavante Dam and Pau Preto Quarry. Paranacythere nigripallus gen. nov. and sp. nov., Velatomorpha xavante sp. nov., and Velatomorpha pseudoaltilis sp. nov. are herein described. The association Velatomorpha–Paranacythere is proposed as typical of Permian mixohaline environments of the Teresina Formation, and is the most abundant in the two studied localities. Paranacythere nigripallus gen. nov. and sp. nov. is proposed to accommodate a very abundant species with typically cytheroidean characteristics, and tentatively ascribed to the family Cytheruridae. Some ecological remarks are presented based on ostracod population age structure, biostratinomy and taxonomic composition of assemblages. The diagnosis of Velatomorpha Tibert & Dewey is emended. Keywords: evolution, marginal marine environments, paleoecology, Teresina Formation, taxonomy.

QUATERNARY-RECENT OSTRACODS (PODOCOPIDA, PLATYCOPIDA) OF THE TYRRHENIAN SEA (ITALY)

The article provides the systematic description of eight species of ostracods described by Dykan (2018, 2020), belonging to the genera Bythocypris, Pontocypris, Pterygocythereis, Bosquetina, Acantocythereis and Cytherella, as well as eleven species in open nomenclature (sp., cf., ex gr.) of the genera Argilloecia, Loxoconcha, Sarsicytheridea, Pontocytheroma, Echinocythereis, Paleoblitacythereis, Pseudobosquetina and Bythoceratina. The ostracods derive from Upper Quaternary, Holocene and modern deposits of the southwestern part of the Tyrrhenian Sea. Sampling stations cover shelf, continental slope and deep water basin in 65-3500 m water depth. The systematic section provides synonymy, detailed descriptions, ecology, geographical and stratigraphical distribution of species. SEM-images of external and internal structures of the carapace like hinge, normal pore canals, macro- and mesosculpture are provided. The documented species belong to North Atlantic, West Atlantic, South Antarctic and Mediterranean zoogeographic groups according to the zoogeographical classification developed for the ostracods of the Tyrrhenian Sea.

Taxonomy and natural history of Cavernocypris hokkaiensis sp. nov., the first ostracod reported from alpine streams in Japan

We describe the cypridoidean ostracod Cavernocypris hokkaiensis sp. nov. from riverbed sediments in an alpine stream at an elevation of ca. 1850 m in the Taisetsu Mountains, Hokkaido, Japan. This species differs from congeners in having (1) the outer surface of the carapace smooth, with sparse, tiny setae, but without shallow pits; (2) the carapace elongate rather than triangular in lateral view; (3) the antennula consisting of seven podomeres; (4) first palpal podomere of maxillula with five dorsodistal and one ventro-subdistal setae; (5) the fifth limb lacking setae b and d; and (6) the fifth limb lacking a vibratory plate. We provided the key to the Cavernocypris species. We determined partial sequences for the cytochrome c oxidase subunit I (COI; cox1) and 18S rRNA (18S) genes in C. hokkaiensis. Our sample contained only females, and we obtained a partial 16S rRNA sequence for the endosymbiotic bacterium Cardinium from C. hokkaiensis, indicating the possibility that this ostracod species reproduces parthenogenetically. Our field survey and observations of captive individuals suggested that C. hokkaiensis may be endemic to the Taisetsu Mountains, with a low population density, narrow distributional range, and slow maturation to sexual maturity.

Neotropical ostracode oxygen and carbon isotope signatures: implications for calcification conditions

Calcitic valves of non-marine ostracodes are important geochemical archives. Investigations of the relationship between the ranges of oxygen and carbon isotope values of modern ostracode populations and their host water provide important information on local or regional conditions and influences. Here we present the first δ18Oostracode and δ13C of the freshwater ostracode species Cytheridella ilosvayi along with the isotopic composition of the waters in which the ostracodes calcified, δDwater, δ18Owater, δ13CDIC values—covering a large geographical range (Florida to Brazil). With this data we extended a newly developed approach based on the estimation of δ18O values of monthly equilibrium calcites as references for the interpretation of δ18Oostracode values. The expected apparent oxygen isotope fractionation between CaCO3 and H2O is correlated with temperature with smaller values occurring at higher temperatures as valid at isotope equilibrium (δ18Ocalcite_eq). Uncertainties about the expected equilibrium calcites derive from incomplete knowledge of high-frequency variations of the water bodies caused by interplay of mixing, evaporation, and temperature. Coincidence between δ18Oostracode and δ18Ocalcite_eq is restricted to few months indicating a seasonal calcification of Cytheridella. There is a characteristic pattern in its difference between mean δ18Oostracode and δ18Ocalcite_eq which implies that Cytheridella provides a synchronous life cycle in its geographical range with two calcification periods in spring (May, June) and autumn (October). This ubiquitous life cycle of Cytheridella in the entire study area is considered to be phylogenetically inherited. It might have originally been adapted to environmental conditions but has been conserved during the migration and radiation of the group over the Neotropical realm.

Application of ostracod-based carbonate clumped-isotope thermometry to paleo-elevation reconstruction in a hydrologically complex setting: A case study from the northern Tibetan Plateau

Paleo-elevation estimates based on the oxygen and hydrogen isotopes of meteoric waters are commonly unreliable in hydrologically complex settings such as the northern Tibetan Plateau (TP), an area of confluence of the East Asian monsoon and mid-latitude Westerlies. Here, we explore a novel application of carbonate clumped-isotope thermometry for estimation of paleo-elevations based on a robust correlation of altitude with modern summer lake-surface temperatures that is independent of moisture sources and recycling processes. Using shallow-lake ostracod species, we estimate a summer lake-surface temperature of ∼ 20 ℃ for the Late Miocene Qaidam Basin of the northern TP. Paleo-elevation calculations yield basin floor estimates of ∼ 3475 m (for ∼ 11 Ma, based on a conventional geochronology model) or ∼ 3375 m (for ∼ 7.0 Ma, based on a revised geochronology model), each with an uncertainty of ±∼950 m, yielding elevations that are close to or slightly higher than the present-day elevation of the study site (∼3200 m). This study highlights the potential of ostracod-based carbonate clumped-isotope thermometry to reconstruct paleo- elevations in hydrologically complex areas of the TP and other montane systems.

Ostracod response to monsoon and OMZ variability over the past 1.2 Myr

We present the first continuous middle through late Pleistocene record of fossil ostracods from the Maldives in the northern Indian Ocean, derived from sediment cores taken at Site U1467 by Expedition 359 of the International Ocean Discovery Program (IODP). Site U1467 lies at 487 m water depth in the Inner Sea of the Maldives archipelago, an ideal place for studying the effects of the South Asian Monsoon (SAM) system on primary productivity, intermediate depth ocean circulation, and the regional oxygen minimum zone (OMZ). The Inner Sea acts as a natural sediment trap that has undergone continuous sedimentation for millions of years with minor terrestrial influence. Our record spans from Marine Isotope Stage (MIS) 35 to the present, covering the mid-Pleistocene transition (1.2–0.6 Ma) and the Mid-Brunhes Event (MBE, at ~480 ka) the time when ice age cycles transitioned from occurring every 40,000 years to 100,000 years. The ostracod data is interpreted alongside the existing datasets from the same site of sedimentological (grain-size) and XRF-elemental analyses, and new organic biomarker data also from Site U1467. These datasets support the paleoenvironmental interpretation of the ostracod assemblages. Ostracods are abundant and diverse, displaying a prominent change in faunal composition at the MBE related to the increase in the amplitude of glacial-interglacial cycles, which deeply affected the monsoon system and thereby the past oceanographic conditions of the Maldives Inner Sea. Furthermore, ostracods exhibit distinctly different assemblages across glacial-interglacial cycles, particularly after the MBE, and these changes convincingly correspond to variability of the OMZ. Glacial periods are characterized by ostracod indicators of well‑oxygenated bottom water due to the intensification of the winter monsoon and the contraction of the OMZ. Abundant psychrospheric ostracods during glacials suggests that a southern sourced water mass, such as Antarctic Intermediate Water (AAIW) and/or Subantarctic Mode water, bathed the Maldives Inner Sea during glacial periods. In contrast, interglacial stages are characterized by ostracod species and biomarker data that indicate low-oxygen conditions and sluggish bottom water circulation pointing to an expansion of the regional OMZ due to the strengthening of the summer monsoon. Our results highlight the sensitivity of ostracods to oceanographic and climate variability.

Freshwater ostracods from an alpine wetland in south-central Anatolia, Turkey

Alpine lakes and wetlands in Turkey remain largely untapped sources of information in terms of both neo- and paleolimnological studies. Such ecosystems experience harsh climate conditions during almost half the year. They are characterized mainly by oligotrophic, freshwater conditions in the absence of direct anthropogenic impacts. This study tracked the distribution of ostracods at a very shallow wetland that is hydrologically connected to the Lake Karagöl (altitude: 2600 m asl) through its outlet, in the Bolkar Mountains, south central Anatolia, Turkey. Four podocopid ostracod species were recorded: Potamocypris fallax Fox, 1967, Stenocypria fischeri (Lilljeborg, 1883), Heterocypris incongruens (Ramdohr, 1808), and Neglecandona sp. Krstić, 2006 throughout a short core from the alpine wetland. Ostracods were especially abundant in the uppermost 4.5 cm of the short core, with Neglecandona sp. most abundant in the uppermost 1 cm. This study shows that populations of H. incongruens and Neglecandona sp. develop at around 15–17 °C mean temperature for the warmest month (August) in the alpine wetland, which is totally frozen during the winter. Potamocypris fallax and Stenocypria fischeri also tolerate these same conditions. Trace metals (Pb, Zn, Cd, Cu, and Ni) were measured, and displayed low concentrations, with only slight fluctuations in Pb and Cu concentrations. Atmospheric contamination does not yet appear to be an environmental threat at this remote site.

Ostracod Response to a Major Middle Jurassic Sea-Level Fall: A Case Study from Southern Tunisia (North Gondwana) with Implications on Regional Stratigraphy and Palaeoenvironmental Reconstruction

Marginal-marine to non-marine ostracod assemblages from the Bajocian (Mid-Jurassic) of southern Tunisia, precisely from the Krachoua Formation at the Kef El Anneba section near the Beni Kheddache area, are here described and tested for their utility to improve the stratigraphic accuracy and palaeoenvironmental reconstructions. This particular microfauna consists of 11 species belonging to 6 genera and represents 2 distinct types of species-rich assemblages from this time interval, allowing the interpretation of the depositional setting of the fossiliferous horizon from which the samples derive. The first ostracod assemblage is mainly composed of the brackish to shallow marine species Fastigatocythere sp. Mette, 1995; Vernoniella aff. V. bajociana Bate, 1965b; Paracypris sp. A, Paracypris sp. B, Fabanella sarda Malz et al., 1985; Marslatourella aff. M. bathonica Andreu, 1999; and Fabanella aff. F. bathonica Oertli, 1957. This ostracod biofacies reflects marginal marine (shallow platform, restricted lagoon) conditions in the studied area. In contrast, the second ostracod assemblage is exclusively dominated by the non-marine limnic species Alicenula sp., Theriosynoecum pusilla Rohr, 1976; Theriosynoecum aff. T. aveyronensis Rohr, 1976; and Theriosynoecum sp. Such ostracod biofacies reflects the establishment of (a) permanent freshwater lake(s) in the studied area, triggered by the total emersion of the Bajocian Krachoua platform, presumably as response to the short-term sea-level fall event JBj3 of Haq (2017). The recognized ostracod species from the upper part of the Krachoua Formation at Kef El Anneba section (Medenine area) are particularly similar to those already described from the neighbouring sections of Kezzani (Dhaher area) and Krachoua (Tataouine area), facilitating a stratigraphic calibration of the Krachoua Formation, as well as regional correlations of the respective Bajocian continental event within the southern Tunisian palaeogeographic domain. Moreover, the biogeography of the studied ostracod microfauna from the Mid-Jurassic of southern Tunisia provides further arguments to support the hypothesis of significant biological exchanges between Laurasian and Gondwanan islands, as recently demonstrated by means of a charophyte microflora, indicating that Peri-Tethyan biogeography remained relatively uniform during that time interval and challenging the previous assumption of their endemism.

First record of the latest Devonian ostracods from Xainza region, Tibet, China: implications on palaeoenvironment and palaeobiogeography

Ostracods of the Devonian–Carboniferous transitional interval in the Lhasa Block are described for the first time at the stratotype section of the Chaguoluoma Formation, Xainza, Tibet. Fifty-three ostracod species of 19 genera are identified and figured including a new species Bairdiacypris xainzaensis n. sp. The ostracod fauna in the Chaguoluoma section may represent an age close to the Devonian–Carboniferous boundary. The benthic ostracods from the Chaguoluoma section belong to the Podocopid association (i.e., Eifelian Mega-Assemblage), which implies an offshore environment. Additionally, ostracods from the Chaguoluoma Formation show a high similarity to the Devonian taxa from South China, suggesting a close biogeographic affinity between the Lhasa Block and South China Plate. They are also compared to the ostracod faunas from Laurentia–Baltica, Gondwana, and Kazakhstan plates, which implies that ostracods could probably benefit from oceanic circulations and sea-level changes to experience faunal exchanges between peri-Gondwana and Laurentia–Baltica during the latest Devonian.