REVUE DE MICROPALEONTOLOGIE最新文献

The study by Gheiasvand and Bartolini (2023) treated Balkhania balkhanica and Torinosuella peneropliformis as morphotypes of a single species, Balkhania balkhanica, leading to incorrect conclusions about its characteristics. Their analysis overlooked key aspects of the life cycle, morphotypes, ecological roles, and paleogeographical distribution of B. balkhanica due to a misunderstanding of foraminiferal systematics. Notably, its megalospheric forms can reach a maximal diameter of 5.2 mm, whereas its microspheric forms may reach up to 15 mm. Its stratigraphic range is limited to the Barremian-early Aptian interval. Although B. balkhanica and Choffatella decipiens share equivalent ecological niches, they are not found together in the same strata. Ch. decipiens has a much wider distribution, over most of the Tethys realm, whereas Balkhania balkhanica is primarily found in the northern Tethys platforms, with the notable exception of Lebanon in the southern Tethys platforms.

This paper describes a new monospecific polycystine radiolarian genus and its single species so far, Pirumosphaera armandae, found in the Southwest Pacific and Indian sectors of the Southern Ocean. The new spumellarian form is rarely found as a complete specimen, as only its first and second shells are commonly found. However, partially complete specimens suggest that the test of this species is made of four shells. The most diagnostic feature of the species is the peculiar shape of the first shell which protrudes through the second shell, a characteristic that does not conform to any other Quaternary spumellarian genus. Based on the distinct and unique relationship between the first and second shells, the species is assigned to the newly established Pirumosphaera genus.

To mitigate ecological and health risks, implementing a comprehensive multidisciplinary monitoring strategy is imperative. This approach aims to effectively identify and record potential declines in water quality and ecological conditions. Utilizing cost-effective and efficient monitoring tools is crucial, especially for developing nations. Despite the previously reported uMlalazi River's pristine status within a protected natural reserve at South Africa's eastern coast, our findings challenge the assumption of its cleanliness, emphasizing the need for ongoing proactive monitoring. Here we reassess the pollution levels and ecological status of aquatic life of the river, and use this to enhance the indicator value of microfauna in South Africa. We analysed 25 surface sediment samples from the uMlalazi estuary, covering a salinity range from oligohaline to euhaline, with a focus on marginal marine Ostracoda and Foraminifera as potential indicators. All samples contained Ostracoda and Foraminifera, with the exception of two. Among the identified ostracod species, there were 17 species belonging to 14 genera. Typical taxa are the brackish water species Perissocytheridea estuaria, Sulcostocythere knysnaenis, and Australoloxoconcha favornamentata. We identified 19 Foraminifera species from 16 genera, with dominant taxa such as Ammonia sp., Quinqueloculina sp., and Miliolinella sp. Three distinct assemblages were observed: A) Ammonia sp. and Quinqueloculina sp., with very low diversity and abundances in general, located along the river course at stations exceeding Pollution Load Index (PLI), which indicates deterioration of sites quality; B) Ammonia sp., Quinqueloculina sp., and Sulcostocythere knysnaenis associated with higher salinity and lower PLI; C) Ammonia sp., Quinqueloculina agglutinans, and Cribroelphidium articulatum located in mudflats with minimal PLI. Our findings align with the commonly observed diversity trend, which indicates reduced species diversity corresponding to elevated pollution levels. Notably, the examined samples revealed a range of Foraminiferal Abnormality Index (FAI) up to 23%, exhibiting anomalies such as multiple tests, changes in coiling, and abnormal chamber shapes. Geochemical analysis indicates that the catchment is subjected to substantial anthropogenic pressure, as evidenced by elevated concentrations of heavy metals, sulphur, and microplastic. Sugarcane farming, urban sewage, titanium mining, and fish farming are the primary sources of pollution in the catchment area. Ongoing investigations in South African estuaries are expanding our dataset and will contribute to a better understanding of the species-specific responses of Ostracoda and Foraminifera to anthropogenic pressure.

Choffatella singularis was described from the Hauterivian of the Paris Basin based on abundant isolated specimens and oriented thin-sections enabling a very detailed description. Although an alveolar wall-structure was mentioned in the original description, the new species was assigned to Choffatella Schlumberger that lacks this feature, instead displaying a fine and regular choffatellid subepidermal network. This feature instead would refer to Pseudocyclammina Yabe and Hanzawa that however has a different apertural type. To accommodate Ch. singularis into the current classification of agglutinated benthic foraminifera and its basic criteria, the new genus Magniezjanninius is established including the new combination M. singularis (Magniez-Jannin).

This study deals with the taphonomy of siliceous microfossils preserved in trace fossils. With this objective, we chose to study trace fossils (Tasselia ordamensis) from the Oligocene Okubo Mudstone Member of the Nishinoomote Formation (Kumage Group), exposed on Tanegashima Island, Kagoshima, southwest Japan. Specifically, we examined microfossil distribution patterns, their mode of occurrence, and state of preservation, within the infill of the trace fossil and as well as from the surrounding host mudstone. This has enabled us to establish that there is a significant siliceous microfossil preservation advantage within trace fossils in mudstones that have been subject to burial diagenesis. The following three conclusions can be made

(1) Relatively well-preserved radiolarian and diatom fossils are distributed unevenly within the trace fossil infills and most of them are interpreted to be derived from passive infilling sediment that was not affected by feeding and excretion activities of the trace maker. (2) Comparing preservation from inside and outside of the trace fossils, the radiolarians from inside the trace fossil are much better preserved than those from outside. (3) Microfossils that were transported into the trace fossil within infill sediment were protected from subsequent burial compaction and diagenesis by preferential cementation to produce a concretion of the trace fossil, and this has enabled the siliceous microfossils to be relatively well-preserved. These results support the idea that trace fossils offer significant microfossil preservation potential. Trace fossils may also be considered as natural archives of valuable micropaleontological records that would usually be lost during burial, compaction and diagenetic processes. Taphonomic analysis of siliceous microfossils within the infills of trace fossils, such as Tasselia ordamensis, has the potential to reveal significant new paleontological insight from sedimentary rocks throughout the fossil record.

Based on sediment traps moored in the southern Ionian Sea (Eastern Mediterranean), this paper documents nassellarian radiolarian occurrences (54 species). Several taxa are reported and illustrated for the first time for the Mediterranean Sea (i.e., Trisulcus triacanthus, Tricerapyris damaecornis, Archiperidium longispinum and Artostrobus joergenseni). Emphasis was placed on the documentation of various ontogenetic stages for some of the encountered species. We also provide a review of the biogeographical distribution for all the confidently identified species, in order to shed light on the provenance of radiolarian fauna in the eastern Mediterranean Sea. Interestingly, despite a majority of warm-water radiolarians, we frequently encountered temperate to cold-water radiolarian species, such as Artobotrys borealis, Artostrobus joergenseni and Archiperidium longispinum.

Sedimentary and paleontological records can be powerful means of reconstructing ecological and physical environmental changes, by using a variety of records extending proxies to extend chronologies beyond the reach of instrumental or manual records. Ostracods are often used as paleoenvironmental proxies. Estimating the population age structure could be a useful tool for assessing the influence of some environmental parameters on death assemblages and for determining the autochthoneity or allochthoneity of the species that make up the thanatocoenosis. In the literature, several methods based on population age structure have been proposed to distinguish autochthonous and allochthonous components of life/death ostracod assemblages.

The Adult:Juveniles ratio analysis of a rich and well-preserved ostracod assemblage from one site in the circalittoral zone of Pontine Archipelago, in the central-eastern Tyrrhenian Sea, is presented. The new Specific Population Stage Index (SPS) is proposed, built upon the measurements of all growth stages in the assemblage. The population structure using the new SPS Index on three different grain sizes is tested against a list of putative in situ and transported ostracod specimens. The analysis on the small grain size (maximum heigth >63 µm) proved the most effective in describing the putative life ostracod assemblage, whereas in the largest grain size (maximum height >180 µm) the young instars of the smaller species are under-represented. This includes species generally under-represented in the fossil record of the Mediterranean, probably due to sample processing bias and not to the rarity of the species itself. Assessing the autochthoneity of modern/fossil assemblages has great potential for acquiring baseline information on ecosystems before the onset of human activities, making this an extremely powerful approach essential to evaluating anthropogenic impacts. This approach seeks to identify the in situ life assemblages within an ostracod population to ensure that paleoenvironmental interpretations are not biased by transported allochthonous elements.

Orbitolina tibetica was described by Cotter in 1929 from the Lhasa terrane of the Tibetan Himalaya, presumably from the Langshan Fm. Since Schroeder (1963), this species has been mainly included in the synonymy of Palorbitolina lenticularis (Blumenbach, 1805). New and detailed images from the type material of O. tibetica reveal that the illustrated specimens in the original description are undiagnostic except one axial section showing the megalospheric embryo, designated herein as lectotype. This section shows that O. tibetica Cotter, 1929 is identical to Mesorbitolina parva (Douglass, 1960) thus becoming its senior synonym and reinstating the new combination Mesorbitolina tibetica (Cotter, 1929) introduced by Zhang (1982, 1994). Consequently, the type-level of M. tibetica (Cotter) cannot be late Barremian-early Aptian, but has to be late Aptian. Tibetella tibetica Zhang, 1994 from the Albian Langshan Fm. with its tripartite embryo is redescribed and also reassigned to Mesorbitolina Schroeder, 1962. As there is neither a junior nor a senior synoym for this new combination, Mesorbitolina zhangi nomen novum is proposed as a replacement name for Tibetella tibetica Zhang, 1994 to avoid a secondary homonymy with M. tibetica (Cotter, 1929).

This study is based on larger benthic foraminifera that dominate the Lower Miocene shelf carbonates of the Qamcheqai section, NW Iran. During the time of deposition, the investigated area was positioned on the Eurasian side of the Tethyan Seaway between the Eastern and Western Tethys. Seven porcelaneous and hyaline perforated species were determined, including Praebullalveolina curdica, Peneroplis evolutus, Androsina cf. diyarbakirensis, Sivasina egribucakensis, Miogypsina cf. intermedia, Operculina complanata, and Amphistegina bohdanowiczi. The presence of Miogypsina cf. intermedia, and Praebullalveolina curdica allowed to correlate the assemblage with SBZ 25 Zone, indicating a Burdigalian age. The results of this study extend the paleogeographic distribution of the endemic taxa Androsina and Sivasina eastwards as far as Central Iran.