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Although the role of Earth’s orbital variations in driving global climate cycles has long been recognized, their effect on evolution is hitherto unknown. The fossil remains of coccolithophores, a key calcifying phytoplankton group, enable a detailed assessment of the effect of cyclic orbital-scale climate changes on evolution because of their abundance in marine sediments and the preservation of their morphological adaptation to the changing environment 1 , 2 . Evolutionary genetic analyses have linked broad changes in Pleistocene fossil coccolith morphology to species radiation events 3 . Here, using high-resolution coccolith data, we show that during the last 2.8 million years the morphological evolution of coccolithophores was forced by Earth’s orbital eccentricity with rhythms of around 100,000 years and 405,000 years—a distinct spectral signature to that of coeval global climate cycles 4 . Simulations with an Earth System Model 5 coupled with an ocean biogeochemical model 6 show a strong eccentricity modulation of the seasonal cycle, which we suggest directly affects the diversity of ecological niches that occur over the annual cycle in the tropical ocean. Reduced seasonality in surface ocean conditions favours species with mid-size coccoliths, increasing coccolith carbonate export and burial; whereas enhanced seasonality favours a larger range of coccolith sizes and reduced carbonate export. We posit that eccentricity pacing of phytoplankton evolution contributed to the strong 405,000-year cyclicity that is seen in global carbon cycle records. .Morphometric analysis of coccolith assemblages spanning the last 2,800,000 years suggests that the evolution of coccolithophores is linked to seasonality changes, paced by Earth’s orbital eccentricity with implications for the carbon cycle.

Paleontology is a natural science discipline based on the observation of fossils. Therefore, paleontology education requires extensive training, and thus significant time, dedicated to observing and describing fossils. In the classroom, teachers often lack sufficient time to showcase the vast majority of key and basic fossil diversity typically encountered in the field. Moreover, students cannot spend enough time in class to properly study each sample. This challenge becomes even more critical in remote learning settings where access to fossils is limited. To address these limitations, we present a remote class dedicated to invertebrate paleontology bachelor’s students, based on a collection of 3D fossils. These models are reconstructed using photogrammetry and hosted online on the Sketchfab web platform. We present a comprehensive Moodle remote course, so-called VirtualPal, that seamlessly integrates instructional videos, interactive 3D fossil models, specific lessons, and formative and summative quizzes. The VirtualPal model can be easily adapted to other observational disciplines such as micropaleontology or petrology but still requires a proper evaluation of its effectiveness using educational science methodologies. La paléontologie est une discipline des sciences naturelles fondée sur l’observation des fossiles. Son enseignement exige donc une formation approfondie, et par conséquent un temps significatif, consacré à l’observation et à la description des fossiles. En salle de classe, les enseignants manquent souvent de temps pour présenter la majorité des fossiles clés et fondamentaux, généralement rencontrés sur le terrain. De plus, les étudiants ne peuvent pas consacrer suffisamment de temps en cours pour étudier chaque échantillon de manière adéquate. Ce défi devient encore plus crucial dans le cadre de l’enseignement à distance, où l’accès aux fossiles est limité. Pour répondre à ces contraintes, nous avons créé un cours à distance de paléontologie des invertébrés dédié aux étudiants en licence, basé sur une collection de fossiles en 3D. Ces modèles sont reconstruits par photogrammétrie et hébergés en ligne sur la plateforme Sketchfab. Dans le detail, le cours complet designé sur Moodle, nommé VirtualPal, intègre de manière fluide des vidéos pédagogiques, des modèles interactifs de fossiles en 3D, des leçons spécifiques, ainsi que des quiz formatifs et sommatifs. Le modèle VirtualPal peut être facilement adapté à d’autres disciplines observationnelles, telles que la micropaléontologie ou la pétrologie, mais nécessite encore une évaluation rigoureuse de son efficacité à l’aide de méthodologies issues des sciences de l’éducation.

Obtaining accurate chronostratigraphic constraints on continental deposits is challenging, necessitating innovative dating approaches. Here, we investigate the feasibility of Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) U–Pb dating of dinosaur eggshell fragments from the Late Cretaceous of Provence, France. Preliminary optical, Scanning Electron Microscopy (SEM), and cathodoluminescence (CL) analyses were critical for identifying zones of optimal preservation and mitigating potential diagenetic contamination. Results from two samples attributed to Megaloolithus mamillare and Cairanoolithus dughii yielded ages of 67.4 ± 4.4 Ma (2s, n = 60 ) and 69.5 ± 9.9 (2s, n = 50 ), respectively, broadly consistent with regional stratigraphic markers. Element mapping reveals significant spatial variation in U and Pb concentrations within individual eggshells, with zones of high contamination contrasting with well-preserved cores. The data highlight the crucial role of diagenesis and organic matter in influencing U–Pb system behavior, although it appears to be limited to early diagenesis. While LA-ICP-MS U–Pb dating of dinosaur eggshells presents substantial challenges, this study demonstrates its potential with careful sample selection and nuanced interpretation, paving the way for further refinement and broader application.

Coccoliths are major contributors to the particulate inorganic carbon in the ocean that is a key part of the carbon cycle. The coccoliths are a few micrometres in length and weigh a few picogrammes. Their birefringence characteristics in polarized optical microscopy have been used to estimate their mass. This method is rapid and precise because camera sensors produce excellent measurements of light. However, the current method is limited because it requires a precise and replicable set-up and calibration of the light in the optical equipment. More precisely, the light intensity, the diaphragm opening, the position of the condenser and the exposure time of the camera have to be strictly identical during the calibration and the analysis of calcite crystal. Here we present a new method that is universal in the sense that the thickness estimations are independent from a calibration but result from a simple equation. It can be used with different cameras and microscope brands. Moreover, the light intensity used in the microscope does not have to be strictly and precisely controlled. This method permits the measurement of crystal thickness up to 1.7 µm. It is based on the use of one left circular polarizer and one right circular polarizer with a monochromatic light source using the following equation: d=λπΔnarctanILRILL, where d is the thickness, λ the wavelength of the light used, Δn the birefringence, and ILR and ILL the light intensity measured with a right and a left circular polarizer. Because of the alternative and rotational motion of the quarter-wave plate of the circular polarizer, we coined the name of this method “bidirectional circular polarization” (BCP).

New sedimentological, biostratigraphical and geochemical data recording the Toarcian Oceanic Anoxic Event (T-OAE) are reported from a marginal marine succession in southern Beaujolais, France. The serpentinum and bifrons ammonite zones record black shales with high (1–10 wt%) total organic carbon contents (TOC) and dysoxia-tolerant benthic fauna typical of the ‘Schistes Carton’ facies well documented in contemporaneous nearby basins. The base of the serpentinum ammonite zone, however, differs from coeval strata of most adjacent basinal series in that it presents several massive storm beds particularly enriched in juvenile ammonites and the dysoxia-tolerant, miniaturized gastropod Coelodiscus. This storm-dominated interval records a marked negative 5‰ carbonate and organic carbon isotope excursion being time-equivalent with that recording storm- and mass flow-deposits in sections of the Lusitanian Basin, Portugal, pointing to the existence of a major tempestite/turbidite event over tropical areas during the T-OAE. Although several explanations remain possible at present, we favour climatically induced changes in platform morphology and storm activity as the main drivers of these sedimentological features. In addition, we show that recent weathering, most probably due to infiltration of O2-rich meteoric water, resulted in the preferential removal of 12C-enriched organic carbon, dramatic TOC loss and total destruction of the lamination of the black shale sequence over most of the studied exposure. These latter observations imply that extreme caution should be applied when interpreting the palaeoenvironmental significance of sediments lacking TOC enrichment and lamination from outcrops with limited surface exposures.

Nannoconus (∼ 5–20 µm) was a major planktonic producer in the Early Cretaceous seas (∼ 150–120 Ma). The heavy calcitic skeletons (micaliths; ∼ 200–1400 picogram) of this extinct nannoplankton genus have contributed to massive carbonate accumulations for over ∼ 30 million years. The micalith microstructure is characterized by an interlocking arrangement of calcitic lamellae spanned around a central canal. The biomineralization process involved in producing the sophisticated micalith is investigated for the first time. Ptychography X-ray computed tomography (PXCT) with synchrotron radiation is applied to an isolated micalith, to obtain a 3D set of tomographic images with ∼ 40 nm spatial resolution. This 3D set was processed to virtually segment the individual calcitic lamella and reconstruct the full micalith through constraining different lengths and angles. The lamellae are repetitively stacked in two distinct inclinations, one following the other, and producing segments combined to form the entire micalith. Individual lamellae were calcified in a “template” of organic layer containing amino acid(s)/biomolecule(s), responsible for creating the interlocking arrangement. Our study of Nannoconus provides a simple yet potent approach to the analysis of biomineralized microstructures characterized by the repetitive arrangement of calcitic units as commonly seen in the calcareous nannoplankton.

The latest Aalenian—early Bajocian time interval (ca. 171-169 Ma) is marked by a global reorganization of oceanic plates with the Central Atlantic opening and the formation of the Pacific plate. This time interval is also marked by a global geochemical perturbation of δ13C with a negative excursion at the Aalenian/Bajocian boundary and a positive excursion during the early Bajocian. Evolutionary diversifications of marine invertebrate taxa, namely ammonites, radiolarians, and coccolithophorids, are recorded at that time. Concerning coccolithophorids, this interval witnesses the diversification and expansion of the most successful Mesozoic genus: Watznaueria. In this study, we explore the potential environmental, ecological, and biological forcing at the origin of Watznaueria diversification and its effect on the coccolith assemblages through quantification of the absolute and relative abundances of calcareous nannofossils in two Middle Jurassic key sections: Cabo Mondego (Portugal) and Chaudon-Norante (France). In both sections, we find an increase in nannofossil absolute abundance and flux at the beginning of the lower Bajocian, coeval with an increase in absolute and relative abundances of Watznaueria spp., followed by a plateau in the middle and upper part of the lower Bajocian. The increase of Watznaueria spp. is synchronous with a decrease in relative abundance of other major coccolith taxa, whereas the absolute abundance of these species did not decrease. During the climatically driven early Bajocian eutrophication event, Watznaueria spp. integrated into the calcareous nannoplankton community in two successive evolutionary steps involving first W. contracta and W. colaccicchii, and second W. britannica and W. aff. manivitiae. Step 1 was driven by an increase in niche carrying capacities linked to the early Bajocian eutrophication. Step 2 was driven by specific adaptation of the newly evolved Watznaueria species to bloom in nutrient-rich environments not exploited before. These evolutionary events have initiated the 100-Myr reign of Watznaueria over the calcareous nannoplankton community.

The rise of calcareous nannoplankton in Mesozoic oceans has deeply impacted ocean chemistry and contributed to shaping modern oceans. Nevertheless, the calcareous nannoplankton colonization of past marine environments remains poorly understood. Based on an extensive compilation of published and unpublished data, we show that their accumulation rates in sediments increased from the Early Jurassic (∼200 Ma) to the Early Cretaceous (∼120 Ma), although these algae diversified up to the end of the Mesozoic (66 Ma). After the middle Eocene (∼45 Ma), a decoupling occurred between accumulation rates, diversity and coccolith size. The time series analyzed points toward a three-phase evolutionary dynamic. An invasion phase of the open-ocean realms was followed by a specialization phase occurring along with taxonomic diversification, ended by an establishment phase where a few small-sized species dominated. The current hegemony of calcareous nannoplankton in the world ocean results from a long-term and complex evolutionary history shaped by ecological interactions and abiotic forcing.

The Early Bajocian, about 172 Ma ago, was a period of tectonic changes, a global carbon-isotope positive excursion, and biological diversification of marine invertebrates (e.g. ammonites, radiolarians and coccolithophores). Unfortunately, both the duration of the Early Bajocian and the associated palaeoenvironmental changes are still poorly constrained. We propose here an estimate of the duration of this sub-stage based on a cyclostratigraphic analysis of the carbonate content from the Chaudon-Norante section, French Subalpine Basin, France. The Chaudon-Norante succession has been correlated with Les Dourbes section using greyscale variations to detect possible local hiatuses. The duration estimated here for the entire Early Bajocian is 4.082 Ma. Two intervals were identified in the positive δ13C excursion: an increase of carbon isotope values lasting 1.36 Ma and climax isotope values lasting for 2.72 Ma. A cooling at high latitudes and warming at low latitudes may have enhanced the Earth's temperature gradient leading to an increase in humidity, which in turn triggered ocean eutrophication at the origin of the δ13C positive excursion.