Orals: Mon, 4 May, 14:00–18:00 | Room -2.93
Identifying the drivers of variation in extinction intensity and selectivity across Earth’s history is essential for explaining past biodiversity patterns and for predicting biological responses to environmental change. Here we investigate the role of coastline geometry and paleogeographic boundary conditions in shaping extinction risk for taxa over the past 540 million years. Paleogeography significantly influenced extinction risk for shallow-marine-restricted invertebrates over the Phanerozoic. Taxa with dispersal pathways that were disproportionately long compared to the latitudinal range traversed, as seen along east–west–oriented coastlines, islands, or inland seaways, consistently showed higher extinction risk compared to taxa whose dispersal pathways allowed more direct movement across latitudes. This information can be leveraged to study how marine invertebrates are responding to present-day climate change. We find evidence of differential dynamics for shallow marine invertebrates today that is dependent on geographic context.
How to cite: Saupe, E., Malanoski, C., Shipley, B., Blake, L., Huang, E., MacNiocaill, C., and Finnegan, S.: Determining the correlates of extinction for marine invertebrates, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5206, https://doi.org/10.5194/egusphere-egu26-5206, 2026.
River ecosystems have been highly altered and modified since the 1950s for water control, navigation, hydroelectricity, and agriculture, leading to hydro-sedimentary changes, vegetation shifts, and ecosystem degradation. In this context, secondary channels were particularly affected, as demonstrated by geomorphological and pollution studies (reduced inflow, accumulation of contaminated sediments). It is also clear that rapid changes in vegetation have taken place, but very few studies exist on this issue.
To address this gap, we propose to study and quantify macrofossils from sediment cores extracted from two side channels of the Rhône River, France. The goal is to reconstruct the history of riparian habitats and biodiversity since the 1950s, linking ecological trajectories to pollution trends (already published) and to engineering actions. This approach helps to provide insights into past human impacts at a high temporal resolution (one sample every two years) and to provide key features for future management strategies in alluvial wetlands.
Several sediment cores were extracted from two side channels, located 50 km south of Lyon (France), in an area heavily equipped (dams, dykes and groynes). Radionuclides (137Cs and 210Pb) and persistent organic pollutant trends were used to date the sediment accumulation. Fifty-two samples were analyzed at 2.5–4 cm resolution, corresponding to a temporal resolution of approximately two years. Plant and animal macrofossils (>400 µm) were recovered, identified, and standardized, with additional characterization of iron slags. Multivariate regression trees were used to highlight temporal succession patterns among taxa.
Macrofossils, especially forest and aquatic taxa, provide a history of habitats and biodiversity since 1950. Three major hydro-ecological phases were identifed and related to local river developments or management. The first phase, before 1977 (date of the dam construction), highlights a diversified riverine forest marked by black alder scales, strawberry seeds and numerous wood fragments. Abundant macrocharcoals and iron slags, correlated with magnetic susceptibility, suggest industrial inputs during this period. Then, the 1980s-1990s represent a second step with the rapid development of terrestrial vegetation with nettles, after dewatering. Finally, around 1999–2000, both sites returned to lentic conditions, with the expansion of wetland and aquatic taxa.
This research demonstrates the value of the macrofossil analysis in order to reconstruct the ecological history of river ecosystems at a high temporal resolution for the last 70 years. The study successfully linked macrofossil data to engineering and management actions, revealing an alternance of riparian dynamics and terrestrialization. These findings provide crucial feedback on the impacts of development, which can be helpful to define reference conditions and monitor long-term ecological changes.
How to cite: Dendievel, A.-M., Riquier, J., Mourier, B., and Winiarski, T.: Environmental shifts revealed by macrofossils and geochemistry in river sediment cores: a high temporal resolution study on the Rhône River (France), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5321, https://doi.org/10.5194/egusphere-egu26-5321, 2026.
The impacts of current and projected global change on fragile high-altitude mountain ecosystems highlight the need to understand how these systems responded to both past climatic variability and human activities in order to better interpret ongoing changes. Throughout the Holocene, a number of disturbances have produced significant impacts on ecosystem functionality. A paramount example is pastoralism in mountain environments, that may have induced modifications and long-term ecological changes. In the Pyrenees, the first and earliest evidence of unequivocal human landscape management has been identified through sedimentary ancient DNA (sedaDNA), revealing an anthropogenic landscape opening linked to the early presence of domestic animals at the lower subalpine belt (Tramacastilla, 1682 m a.s.l.) ca. 6 ka BP. In this research we present a new record of landscape evolution and human activity presence at the upper subalpine boundary of the Pyrenees by analyzing sedaDNA at Basa de la Mora lake (BSM, 1913 m a.s.l; central Pyrenees).
We recovered a new lacustrine sequence from BSM to reconstruct Holocene plants and animal communities using sedimentary ancient DNA (sedaDNA), together with additional proxies to infer fire activity and temperature variability. These results are compared with the Tramacastilla lacustrine record and its sedaDNA reconstruction in order to identify differences in human land-use practices across subalpine ecosystems at different elevations during the last 9 ka BP.
Our result proves two contrasting cases of landscape management and plant community responses to disturbance in high-altitude environments during the same chronological period: Tramacastilla primarily shaped by human management, where diversity patterns dramatically change with human activity, and Basa de la Mora, mainly responding to natural disturbances such as fire and temperature variability.
How to cite: Ramos Capon, C., González-Sampériz, P., Julián-Posada, I., Epp, L., Garcés Pastor, S., Bover, P., and Gil Romera, G.: The pastures were greener over there: Contrasting human management in Pyrenean subalpine ecosystems through sedaDNA , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11257, https://doi.org/10.5194/egusphere-egu26-11257, 2026.
Ecological and environmental estimates derived from paleontological data may be distorted due to taphonomic biases and time averaging. To assess how well fossils preserve ecological and environmental information, we compared multi-taxic macroinvertebrate benthic communities (135 species from 6 phyla) with sympatric skeletal accumulations (death assemblages; 150 species) for 52 coastal sites in North Carolina (USA). The series of resulting studies indicate that death assemblages have high informative value, and their fidelity relative to living communities is remarkably robust. First, the assessment of live-dead faunal composition captured community organization along an onshore-offshore depth gradient. In multivariate ordinations Axis 1 locality scores correlated significantly with locality water depth, and taxon scores were concordant with the observed occurrences of taxon depths. Moreover, the live and dead datasets yielded consistent habitat delineations in multivariate ordinations. This direct test across modern sites with known bathymetry supports the use of multivariate proxies derived from benthic marine death assemblages as a quantitative proxy for water depth. In addition, dead mollusks were an excellent proxy for all taxa when tracking depth gradients. Second, although community composition differed between the live and death assemblages, these differences were predictable with an overabundance of phyla and classes with robust skeletons in death assemblages. Third, compositional spatial heterogeneity (beta diversity) did not differ significantly between live and dead whether using all organisms, only mollusks, or only non-mollusks. These congruent estimates suggest that mollusks alone can also serve as reliable surrogate community proxies for beta diversity. Finally, high live-dead fidelity is also supported by congruence in quantitative indices of functional diversity (functional richness, redundancy, and vulnerability), biological traits, overlap in multidimensional functional space, and species distributions among functional groups. That is, despite the overabundance of mollusks and other skeletonized taxa, the live and dead estimates of functional diversity were concordant. Consistent with previous work in other study systems, these results indicate that shallow marine death assemblages can yield robust ecological estimates adequate for assessing the historical variability of ecosystems. Despite filters imposed by differential preservation and time averaging, the fossil record is likely reliable with respect to relative comparisons of biodiversity and ecology across shallow benthic marine assemblages. The high spatial fidelity of death assemblages supports the emerging paradigm of Conservation Paleobiology that paleontological data can quantify anthropogenic changes in marine ecosystems and advance our understanding of spatial and temporal aspects of biodiversity.
How to cite: Kowalewski, M. and Tyler, C.: High Ecological and Environmental Fidelity of Marine Benthic Fossil Assemblages, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1822, https://doi.org/10.5194/egusphere-egu26-1822, 2026.
Biominerals, such as marine macroinvertebrate shells, represent valuable archives for the reconstruction of recent and past environmental conditions. Brachiopod shells are among the most reliable high-resolution biomineral archives of climate and environmental change, as they resist diagenetic alteration due to their low-Mg calcite composition, are abundant and widespread in the fossil record, and precipitate shell material close to isotopic equilibrium with ambient seawater, with limited vital effects. Studying modern brachiopod shells is therefore key to assessing their potential as reliable archives to reconstruct past dynamics of species and ecosystem changes at different scales from decades to millions of years.
Previous research has focused extensively on the micro- and nanostructure of modern brachiopod shells, yet our understanding of their mesoscale structural patterns remains limited. Moreover, few studies have investigated the relationship between shell microstructure and geochemical variation, and existing results are often contradictory; in this context, mesoscale patterns may provide a means to assess potential microstructural control on geochemical signatures. This study examines the organization, arrangement, and thickness of different shell fabrics (i.e., primary dendritic, secondary fibrous, and tertiary columnar) to identify systematic patterns of variation at interspecific, intraspecific, and intra-shell levels and how these relate to geochemical variation. A microstructural analysis of several two- and three-layered modern brachiopod shells was performed using a scanning electron microscope (SEM). Specimens belong to eight terebratulid and rhynchonellid species from different settings and water depths.
Results reveal differences between the three-layered species: G. vitreus exhibit a more regular and well-organized microstructure, whereas L. neozelanica has frequent intercalations of fibrous and columnar fabrics. The two species differ in their posterior shell region, where G. vitreus is dominated by the tertiary layer, whereas L. neozelanica is composed almost entirely of fibers. In both species, the tertiary layer is thickest in the central portion of the shell and progressively thins toward the anterior margin, where it eventually disappears. These results suggest that microstructure does not exert a primary control on geochemistry, as similar isotopic patterns reported by Crippa et al. (2025) are observed in both species despite their microstructural differences. Two-layered species exhibit interspecific variation while maintaining the typical shell architecture composed of an external thin primary layer and an inner fibrous fabric. Although L. uva is typically classified as a two-layered species, small prism-like elements resembling tertiary columnar structures were observed intercalated with fibers, particularly toward the interior of the shell. Layers of calcitic pads were observed at the anterior margin of L. uva, forming when a rapid mantle retraction temporarily halted secretion, after which carbonate deposition resumed at new sites.
Future research should integrate these mesoscale structural patterns of modern brachiopod shells with high-resolution geochemical analyses to advance our understanding of brachiopod biomineralization and further assess their reliability as environmental proxy archives.
References:
Crippa, G. et al. (2025). Brachiopods as archives of intrannual, annual, and interannual environmental variations. Limnology and Oceanography Letters, 10(3), 390-402.
How to cite: Cervellieri, M., Crippa, G., and Angiolini, L.: Testing the biomineral archive: microstructural patterns of modern brachiopod shells, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13327, https://doi.org/10.5194/egusphere-egu26-13327, 2026.
Worldwide, coral reefs are declining due to a combination of local and global stressors. In the Red Sea, these pressures have affected hard coral cover, altered community composition, and reduced coral colony size. However, the lack of long-term historical data in this region makes it difficult to accurately quantify the extent of reef degradation. Establishing regional baselines that represent pre-anthropogenic, pristine reef conditions is therefore essential. Pleistocene reefs provide a unique opportunity in this regard, offering insights into reef community structure and composition in the absence of recent anthropogenic disturbance. In this study, we conduct, for the first time, a quantitative comparison between a Pleistocene (Marine Isotope Stage 5e; ~125,000 years ago) fossil reef and an adjacent modern reef in northern Egypt to assess the current state of the modern reef. Our results show that the fossil reef had larger colony size in four of the five most abundant genera and the overall community composition differed significantly between the fossil and modern reef. Our findings also suggest that massive corals may be more suitable than branching corals for comparisons of coral colony size distributions due to their better preservation potential in the fossil record. While some observed differences may stem from taphonomic processes, time-averaging and environmental differences, we argue that most of the disparity reflects genuine degradation in the modern reef.
How to cite: Zuschin, M., Ivkić, A., Jones, L. A., Kroh, A., Mansour, A., Osman, M., and Hassan, M.: Reconstructing ecosystem baselines using Pleistocene data: insights from an Egyptian coral reef, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20971, https://doi.org/10.5194/egusphere-egu26-20971, 2026.
The evolution of vegetation types (herbaceous vs. woody; C₃ vs. C₄ plants) on the Chinese Loess Plateau (CLP) is highly sensitive to regional climate variability and closely linked to changes in solar radiation and the intensity of the East Asian Summer Monsoon (EASM). However, drivers of vegetation change on the CLP, including the timing and nature of human activities as an ecological influence remain subjects of ongoing debate. Here, we reconstruct vegetation evolution over the past ~34 kyr BP using biomarker evidence from a lacustrine sedimentary sequence from Tianjiao Lake in the southern CLP. Multiple proxies, including total organic carbon (TOC), carbon isotopic composition of bulk organic matter (δ¹³Ctoc), n-alkane distribution indices (e.g. C₃₃/(C₂₇+C₃₃)), and carbon isotopes of n-alkanes (δ¹³Cₐₗₖ), are used to infer changes in plant functional types and photosynthetic pathways.
The results indicate that vegetation throughout the last 34 kyr consisted of a mixture of C₃ and C₄ plants, with C₃ herbs remaining dominant. Between 34 and 15 kyr BP, weaker solar radiation and reduced monsoon intensity produced relatively cold and dry conditions, limiting biomass production and suppressing C₄ plant abundance. After ~15 kyr BP, intensified solar radiation and monsoon strength led to warmer and more humid conditions, promoting vegetation expansion and an increased contribution of C₄ plants, although C₃ herbs continued to dominate. From ~2.7 kyr BP onward, signals of human activity increasingly overprint climatic controls, indicating that anthropogenic disturbance became the primary driver of vegetation change on the CLP.
These findings demonstrate the effectiveness of n-alkane biomarkers for reconstructing long-term vegetation dynamics on the Loess Plateau and highlight the increasing role of human activities in reshaping plant communities during the late Holocene. The results provide important context for understanding ecosystem responses to future climate change and anthropogenic pressures in this environmentally sensitive region.
How to cite: Pang, Y., Zhou, B., and Meadows, M.: Vegetation evolution and its driving mechanism on the Chinese Loess Plateau over the past 34 kyr, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9149, https://doi.org/10.5194/egusphere-egu26-9149, 2026.
Two generations of palaeolakes (Lipowo I, Lipowo II), associated with the termination of the Last Glacial, were documented in the Suwałki Lake District, northeastern Poland. Multiproxy analyses and radiocarbon (14C) and OSL dating were performed on lacustrine sediments. The older generation of basins developed among gradually melting dead-ice blocks and was eventually buried under mineral deposits at the end of the Allerød. The younger generation formed after the complete melting of dead-ice blocks and reflects environmental changes from the late Allerød to the Holocene. Observed changes in sedimentation style during the Late Glacial and early Holocene were linked to significant climatic shifts and their consequences. These changes were also recorded in palynological analyses, fossil Cladocera, geochemical data, and stable isotope results.
The vegetation composition during the Younger Dryas shows distinct regional features, including the strong development of Juniperus shrubs and herbaceous and grassy plants at the beginning of this stage, as well as the appearance of Picea abies in its later part. Northeastern Poland was more similar to northeastern Europe than to the rest of the Polish Lowlands, reflecting the paleoclimatic gradient that occurred in Poland during the Younger Dryas. The Holocene section of the Lipowo II profile also documents the first cold Holocene event at 11.4 ka.
Cladocera analysis for the studied lakes revealed remains of only 10 species in Lake “Lipowo I,” belonging to three families: Chydoridae, Bosminidae, and Daphniidae, with most remains attributed to Chydoridae. These species were mainly cold-water tolerant, and their frequency was low (max. 2200 ind./cm³). In Lipowo II, 25 Cladocera species were identified, representing various ecological zones, including open-water taxa requiring higher water temperatures. The number of individuals increased to a maximum of 6000 ind./cm³, indicating more favorable conditions for Cladocera development. Environmental changes recorded in vegetation and zooplankton are further supported by stable isotope analyses. Total organic carbon (TOC) and total nitrogen (TN) increased from approximately 2% to 53% and from 0% to 3.8%, respectively. Multiproxy analyses enabled the reconstruction of significant environmental changes associated with the transition from glacial to interglacial conditions in northeastern Poland.
How to cite: Niska, M., Rychel, J., Sokołowski, R., Miroslaw-Grabowska, J., Obremska, M., and Kramkowski, M.: Two generations of Late Glacial palaeolakes: insights from multiproxy analyses (Suwałki Lake District, Poland), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19067, https://doi.org/10.5194/egusphere-egu26-19067, 2026.
Mesopelagic ecosystems are vital to the ocean’s health yet face unprecedented threats due to accelerating climate change. Lanternfish (family Myctophidae) are key sentinels of midwater ecosystem health because they dominate mesopelagic fish biomass and mediate energy, nutrient, and carbon transfer across ocean layers. Despite their ecological importance, very little is known about their potential response to climate change stressors due to logistical challenges when studying mesopelagic ecosystems. We use thousands of fossil fish otoliths (calcium carbonate ear stones) recovered from marine surface sediments to reconstruct lanternfish growth, body size and energetic investment across contrasting oceanographic regimes. We compare assemblages from the highly productive, but oxygen-poor Tropical Eastern Pacific (TEP) and the oligotrophic, well-ventilated Caribbean, to test how oxygen availability and food supply shape mesopelagic fish energetics across the Isthmus of Panama. Otoliths from marine sediments serve as a cost-efficient, powerful archive to overcome methodological barriers and allow us to reconstruct long-term changes in lanternfish dynamics. We quantify energetic changes in lanternfish assemblages by reconstructing lanternfish body size estimates and mean per-capita biomass from otolith measurements and growth trajectories derived from increment biochronologies. Our results reveal anomalously small lanternfish in the TEP today, despite the region’s tendency to host larger fishes relative to the Caribbean, providing the first indication that mesopelagic fish size is potentially related to oxygen limitation. We then extend this approach to fossil otoliths to explore changes before the closure of the Isthmus of Panama using the Late Miocene/Pliocene as an analog system for warmer than modern conditions to test how mesopelagic ecosystems might respond to future climate change. We find that lanternfish dominated Panama’s ancient fish assemblages in the Caribbean but declined in relative abundance toward the Isthmus closure, while their mean per-capita biomass remained stable over the past 8 Ma. These results imply higher lanternfish biomass during periods of prolonged warming and lower biomass under less productive, better-oxygenated Caribbean conditions created by the Isthmus uplift. Yet in contrast to Panama’s geological past, our results suggest that oxygen availability exerts a dominant control on lanternfish energetics and production in the modern TEP. By integrating otolith archives from deep time to the recent past, we mapped shifts in lanternfish energetics in response to major environmental changes, revealing their sensitivity to oxygen availability and indicating that projected ocean deoxygenation might constrain the energetic capacity of the mesopelagic zone in a future ocean.
How to cite: Pallacks, S., Dillon, E., De Gracia, B., Mora, J., Leonhard, I., Godbold, A., Lueders-Dumont, J., Lin, C.-H., Finnegan, S., A. Klompmaker, A., and O’Dea, A.: Fossil otolith archives reveal changes in mesopelagic fish energetics across the Isthmus of Panama over the last 8 million years, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12480, https://doi.org/10.5194/egusphere-egu26-12480, 2026.
Fossil shells of marine bivalves such as giant Tridacna provide unique information on past environments with seasonal to daily resolutions. Changes in mean seasonal cycles and inter-annual variability can be reconstructed by sequentially analyzing the composition of the annual layers of calcium carbonate. We present a new calibration study of 5 modern Tridacna squamosa which have been collected in Belitung Island, Indonesia, on the path of the Karimata Strait during different years 2016-2025. At this locality, the seasonal cycle is characterized by a double seasonal peak in sea surface temperature due to the inversion of surface currents associated with the SE and NW monsoons. We analyzed both the stable isotope (del-18O, del-13C) and trace element profiles (Mg/Ca, Ba/Ca). The aim of this study was to demonstrate the reproducibility of the trace elements between samples collected on different dates in the same site. The lifespan of the specimen collected were 2 to 5 years long and geochemical profiles showed significant overlap between modern dead-collected specimen. The results show that Ba/Ca records are highly reproducible between samples exhibiting a single seasonal peak during the period May-June. Mg/Ca show a good reproducibility between samples exhibiting a double seasonal peak. We compared our records to local hydrology: sea surface temperature, rainfall and productivity. Mg/Ca shows a clear relationship with SST. Ba/Ca has previously been shown to reflect both productivity and/or riverine sources of Barium. At Belitung site there are 2 seasonal increases in productivity, and the shell Ba/Ca only increases during the may-june period highlighting a more complex relationship than previously observed
How to cite: Elliot, M., Boutreux, C., Cahyarini, S. Y., Vidal, L., La, C., and Lo, L.: Stable isotopes and trace element profiles of modern giant clams Tridacna squamosa from the Karimata Strait : a calibration study., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18799, https://doi.org/10.5194/egusphere-egu26-18799, 2026.
For more than 30 years, stable carbon and oxygen isotopic analyses of herbivore skeletal tissues have been widely used to reconstruct animal life history and behavior, including diet, physiology, mobility, and past climate and environmental conditions. Tooth enamel is particularly well-suited for such investigations because its high crystallinity and low organic content confer exceptional resistance to diagenetic alteration, preserving primary isotopic signals over geological timescales. Moreover, because enamel forms incrementally, it enables the extraction of isotopic time-series information that reflects the period of tooth mineralization.
Here, we explore the potential of stable isotope analysis to maximize paleoecological data retrieval from Paleolithic faunal assemblages, using the archaeological site complex of Melka Kunture (Upper Awash, Ethiopia) as a case study. Melka Kunture is a dense cluster of Pleistocene and Holocene sites located in the Ethiopian highlands at elevations of 2000-2200 m above sea level, and it is inscribed on the UNESCO World Heritage List. Its geoarchaeological sequence, dated between 2,000,000 and ~5,000 years ago, provides a rare opportunity to investigate high-elevation past ecosystems in the tropics, where collagen preservation is often poor and enamel-based approaches are particularly valuable. By combining bulk and intra-tooth isotope analyses of herbivore tooth enamel with faunal, pollen, and phytolith evidence, we assess the complementarity of proxies to detect climatic and environmental variability over time and its implications for human and mammalian evolution. The results demonstrate how stable isotope analysis can substantially enhance the interpretation of Paleolithic records, particularly in ecologically marginal settings. Finally, we highlight the value of integrated, multi-proxy approaches when reconstructing past ecosystems
How to cite: Briatico, G., Melis, R. T., Geraads, D., Mutri, G., Hailu, H., and Mussi, M.: High-elevation climatic and environmental variability during the early hominin occupations at Melka Kunture (Upper Awash, Ethiopia), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20354, https://doi.org/10.5194/egusphere-egu26-20354, 2026.
The palaeoanthropological site of Ruidera [1], discovered in 2018, provides a unique high-resolution window into the ecosystem dynamics of the Iberian Peninsula during the late Middle Pleistocene (ca. 300 kyr). Characterized by remarkable abundance and preservation of human and macro-mammal fossils, the assemblage includes a diverse suite of taxa, including European tahr, deer, horses, and a dense guild of carnivores such as lions, leopards, lynxes and wolves, as well as some mesofauna remains such as rabbits and birds. This study presents a preliminary palaeoecological reconstruction of the site through stable isotope analysis (δ13C, δ18O) of tooth enamel across six different taxa, including carnivores, herbivores and hominins.
This study’s purpose is to make a first approximation to the ecosystem present in Ruidera during this period, focusing on the hypothesis that it could present a Mediterranean landscape similar to the current one and typical of the Iberian Peninsula, but not discarding some potentially small variations in comparison to other Iberian records, given its more southern latitude. The isotopic data available from other Middle Pleistocene Iberian sites (Punta Lucero, northern Spain [2]; and Sierra de Atapuerca complex: Trinchera Dolina (TD10+TD11) [3], Sima de los Huesos [3,4] and Trinchera Galería (GII+GIII) [3]) will be compared to that obtained for Ruidera.
The Ruidera isotopic data infer a Mediterranean ecosystem defined by a degree of aridity previously unrecorded in the Iberian Middle Pleistocene, at least through stable isotope analysis. The significantly positive δ13C values suggest a water-stressed environment, likely representing one of the most xeric records for this chronology in the Iberian Peninsula. Furthermore, δ18O values align closely with those from the coastal site of Punta Lucero; yet diverge considerably from the more continental inland records of the Sierra de Atapuerca complex. This could suggest a distinct regional climatic pocket for Ruidera, influenced by both Mediterranean aridity and specific topographic effects.
Taphonomic analysis and the faunal list indicate an environment characterized by the ecological biases of mountainous terrain, with a strong signal of accumulation by carnivores. Within this framework, the trophic position of the Ruidera hominin was evaluated. The results indicate that the hominin occupied an isotopic niche closely similar to that of the leopard (Panthera pardus) at the same site. This suggests a specialized, high-protein diet consistent with other European Middle Pleistocene records [5].
In conclusion, the Ruidera site stands out as a unique climatic outlier within the Middle Pleistocene Iberian record. The inferred environment is one of a quite arid Mediterranean landscape where hominins habited within a carnivore-dominated community. These preliminary results underscore the environmental heterogeneity of the Iberian Peninsula and the capacity of Middle Pleistocene fauna and human populations to adapt to different paleoclimatic conditions.
References:
[1] García-Martínez et al. 2022. Cuaternario y Geomorfología. 36, 7–35. https://doi.org/10.17735/cyg.v36i1-2.90422
[2] Domingo et al. 2017. Quaternary Science Reviews. 169, 243–262. https://doi.org/10.1016/j.quascirev.2017.06.008
[3] García García et al. (2009). Journal of Archaeological Science. 36, 1142–1151. https://doi.org/10.1016/j.jas.2008.12.018
[4] García García et al. (2015). PLOS ONE. 10, e0142895. https://doi.org/10.1371/journal.pone.0142895
[5] Ecker et al. (2013). Journal of Human Evolution. 65, 363–373. https://doi.org/10.1016/j.jhevol.2013.06.013
How to cite: Sanz-Henche, P., García-Martínez, D., Pérez de los Ríos, M., Palancar, C. A., Díaz-Pérez, S., Aranbarri, J., Bermejo, L., Campaña Lozano, I., Cambra-Moo, Ó., Cifuentes-Alcobendas, G., Estalrrich, A., Rufà, A., and Fidalgo, D.: Preliminary palaeoecological reconstruction of the Ruidera site (Middle Pleistocene, Southern Iberian sub-plateau)., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19018, https://doi.org/10.5194/egusphere-egu26-19018, 2026.
Understanding the complex interactions between organisms and their environment is fundamental for palaeoenvironmental and palaeoclimatic reconstructions. Biotic and abiotic components evolve through time and leave imprints in the biosedimentary record, which can be unravelled to trace how ecosystems respond to palaeoenvironmental changes. In this study, we apply an integrated approach combining sedimentological and palaeoecological analyses to reconstruct the palaeoenvironmental evolution of the Rio Stramonte section (Lugagnano Val D’Arda, Emilia Romagna, Italy) within a key climatic interval, the Piacenzian, which is the most recent example of prolonged global warming in the deep time record and a possible analogue for the future climate conditions. The Rio Stramonte section is 54 m thick and is assigned to the Late Pliocene (Piacenzian) based on preliminary biostratigraphic analyses (molluscs, foraminifera and nannofossils). Twenty-eight mollusc samples were collected for palaeoecological analysis, and a total of 3147 specimens belonging to more than 120 taxa of bivalves and gastropods were identified and studied. The palaeoecological analysis shows that mollusc assemblages are composed of both infaunal and epifaunal taxa of infralittoral and circalittoral settings. The sedimentological analysis indicates a vertical succession of lithofacies suggesting an overall regressive trend from the bottom to the top of the section, with variations in water depth (from approximately 40–50 m to 5–10 m) and sedimentation rates. In the lower part of the section sandy beds are rich in molluscs. Bivalve specimens mainly occur with disarticulated valves, however without evidence of corrasion, thus reflecting a short-distance transport. In the middle part of the section, composed of fine-grained sediments deposited in a shelf setting, specimens are preserved in life position indicating low-energy muddy bottoms. Finally, the upper part of the section is rich in bivalve and gastropod fragments due to transport processes. Indeed, in this part of the section sedimentological features, as hummocky cross stratification, probably related to storm waves, indicate a shallower environment compared to the lower and middle part of the section, possibly affected by density flows directly related to river floods. Based on sedimentological and palaeoecological analyses, the Rio Stramonte section deposited in a shallow-water marine environment (infralittoral to shallow circalittoral) affected by episodes of salinity reduction due to river discharge. These results contribute to a better understanding and characterisation of the mollusc faunas of the Palaeo-Adriatic Basin during the warm climatic interval of the Piacenzian.
How to cite: Chiari, A., Felletti, F., Marino, M., Petrizzo, M. R., Raineri, G., and Crippa, G.: Integrated sedimentological and palaeoecological analysis of the Upper Pliocene Rio Stramonte section (Emilia-Romagna, Italy), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5535, https://doi.org/10.5194/egusphere-egu26-5535, 2026.
Understanding the relationship between palaeoenvironmental change and vertebrate evolution and ecology through deep time has historically been examined in the context of faunal responses to climate parameters estimated from lithologic, palaeobotanical and stable isotopic proxies. Conversely, recent advances in the application of ecometrics, trait-environmental relationship models rooted in functional factors such as mechanical performance and metabolic tolerance, provide taxon-free estimates of palaeoclimate that can be applied across multiple temporal and spatial scales. The Miocene sedimentary sequences of the Nyanza Rift in Western Kenya includes a temporally-constrained and dense vertebrate fossil record as well as climate proxies that can be combined to examine equatorial palaeoenvironments during globally warm intervals. We reconstructed body size distributions and quantified axial skeletal morphologies for fossil reptile communities at multiple localities to constrain minimum ambient temperatures necessary for efficient metabolism based on metabolic theory as well as infer palaeoprecipitation values based on locomotory modes reconstructed from skeletal morphometrics. Estimates based on the reptile record are consistent with values derived from local palaeobotanical data and demonstrate warmer, wetter climates in the Early Miocene, with shifts toward slightly drier climates by the early Middle Miocene. These results demonstrate the utility of the vertebrate fossil record for reconstructing palaeoclimates and provide new proxies for non-analog environments of the past.
How to cite: Head, J., McGuire, J., Manthi, F. K., Peppe, D., Cote, S., McNulty, K., and Lawing, A. M.: Combining phenotypic functional traits and metabolic theory to reconstruct Miocene equatorial palaeoclimates from the reptile fossil record., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15318, https://doi.org/10.5194/egusphere-egu26-15318, 2026.
The exact genesis and function of ammonite sutures have long been sought as a simple answer and debated fiercely for decades. While possible functions of the highly iterative septal fluting, particularly that seen in the Jurassic and Cretaceous, may be complex, multifaceted, and mutually inclusive, the true mechanism for the formation of ammonite sutures almost certainly contraindicates all other possible methods of generation, and as a result, has been particularly unsettled in paleobiological literature. Reasons for ammonite suture complexity have been discussed both formally and informally in the ammonoid community and include capillary maximization of cameral fluid, age-related wrinkling of the rear mantle, branching of soft tissues in the rear mantle that compare with dendronotid sea slugs, survival of bite force or increased water pressure as per the Westermann morphospace, and the famous “tie points” and “viscous fingering” models of the mid-twentieth century. Here, we present evidence of another impetus for high complexity in ammonite sutures: cold seawater. We examine the strengths of ammonite suture complexity as a standalone or auxiliary index of sea-surface temperature and paleoclimate data that follows the same patterns as δ18O ratios, particularly in cool conditions, such that ammonites whose isotopes indicate a cooler climate tend to have high fractal complexity in the adult (and sometimes juvenile) stages. Coldwater ammonite faunas exclusively exhibit septa with fractal dimensions in the highest possible ranges (Df > 1.6), such as the transition from temperate to cold conditions between the Campanian and Maastrichtian Stages on the Antarctic peninsula. Ammonite sutures also follow clear patterns of increasing fractal complexity descending thermoclines in a single locality, such as the Western Interior Seaway. Although it is impossible to standardize overall sea-surface temperature (SST) through stable isotope ratios, which require context-specific isotope examination, our results suggest that septal organogenesis of Late Mesozoic ammonites is deeply linked to climate-driven physiological inputs such that ammonites may be a functional tool for understanding Cretaceous ocean temperatures. Ammonite sutures simplify paleoclimate analyses in the Cretaceous because their fractal complexity seems to always follow a temperature-driven pattern, helping to reduce the noise around δ18O from locations with complicated isotopic contexts, such as the Western Interior Seaway. We intend to continue this work to further develop and understand the full implications of fractal analysis of ammonite sutures as a novel tool for reconstructing Cretaceous paleoclimate.
How to cite: Marriott, K., Tran, M., Zhang, E., Stormlance, O., Chen, A., and Guo, W.: Ammonite suture complexity as a paleoclimate indicator comparable to δ18O stable isotope ratios, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4310, https://doi.org/10.5194/egusphere-egu26-4310, 2026.
The phenomenon of polar amplification causes high-latitude warming to exceed the global mean and enhances seasonal variations in temperature and precipitation. As such, it complicates the understanding of both modern and past global warming impacts in polar regions. Characterizing the climate change in polar regions is further hampered by limited data coverage and persistent challenges in interpreting local paleoenvironmental archives.
To help address these knowledge gaps, we present bulk and seasonally resolved stable oxygen (δ¹⁸O) and clumped isotope (Δ₄₇) data from exceptionally well-preserved bivalves from the Early Jurassic North Pole (eastern Siberia), spanning the late Pliensbachian icehouse-Toarcian hothouse transition. Upper Pliensbachian Harpax specimens show pronounced seasonal δ¹⁸O variability of 1.5-6 ‰, corresponding to apparent temperature ranges of 6-26 °C assuming invariant seawater δ¹⁸O. In contrast, seasonally resolved clumped isotope data do not yield a statistically significant seasonal temperature difference (1.4 ± 1 °C). Together with a low mean Δ₄₇ temperature of ~3.5 ± 1 °C, this discrepancy implies that the large δ¹⁸O amplitude reflects strong seasonal variability in seawater δ¹⁸O, likely driven by enhanced precipitation, and/or meltwater input in a relatively proximal sedimentary setting with near-freezing mean annual temperatures.
By contrast, Toarcian Dacryomya jacutica specimens show reduced δ¹⁸O variability of 1-2 ‰ (~4-8 °C) and a larger, statistically significant seasonal Δ₄₇ temperature difference of 5.9 ± 1.3 °C, with a mean Δ₄₇ temperature of ~10.3 °C. The agreement between δ¹⁸O and Δ₄₇-derived seasonality indicates a limited contribution of seawater δ¹⁸O variability during the Toarcian and points to a shift toward more distal sedimentary conditions. Collectively, these results provide one of the first quantitative constraints on Arctic temperature seasonality under greenhouse climate conditions in deep time.
How to cite: Krizova, B., Letulle, T., Daëron, M., Vinçon-Laugier, A., Rogov, M. A., Lutikov, O. A., Donnadieu, Y., and Suan, G.: Polar temperature seasonality from the Early Jurassic, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18109, https://doi.org/10.5194/egusphere-egu26-18109, 2026.
A new book on the Carnian Pluvial Episode in Austria and the history of 150 years of scientific excavations is presented (Lukeneder A ed. 2026). It is nearly 40 years since Alastair H. Ruffel and Mike J. Simms stumbled upon the realisation that the Carnian Stage of the Late Triassic had experienced a dramatic episode of climate change that had profoundly affected the Global biota (Simms and Ruffell 1989; Simms et al. 1994).
Although the work of these authors more than 30 years ago recognized the widespread biotic changes seen through the Carnian Stage, they were unaware of an additional fascinating element of this interval, that of the Early Carnian Konservat-Lagerstätten (Lukeneder A and Lukeneder P 2021) described in this volume. Previous publications relating to these Lagerstätten occur scattered through literature spanning more than a century, but by bringing together a diverse range of geoscientists to address multiple aspects of this particular example at a key time during Earth history, this volume can substantially increase awareness of it. Given the importance of the CPE in Earth history, the Austrian Triassic Konservat-Lagerstätten must now rank alongside others with a higher profile and long history of research: Ediacara and counterparts at other sites around the world, the Burgess Shale, and the Solnhofen Limestone.
The chapters in this new multi-author volume fall into three broad categories: documentary, covering the history of research here and an exploration of techniques; paleontological; and stratigraphic, encompassing paleontology, mineralogy and geochemistry. The depth and diversity of the contributions in this volume add greatly to the knowledge of the CPE and how it developed.
How to cite: Lukeneder, A.: Late Triassic Konservat-Lagerstätten within the Carnian Pluvial Episode in Austria, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1483, https://doi.org/10.5194/egusphere-egu26-1483, 2026.
Abstract: The End-Triassic Mass Extinction (ETE) exerted a profound impact on marine ecosystems. It is widely accepted that the primary trigger was the massive volcanic eruptions of the Central Atlantic Magmatic Province (CAMP). While environmental perturbations during this event have been extensively documented in the Western Tethys, high-resolution studies in the Eastern Tethys remain limited. This study presents a continuous Triassic-Jurassic marine succession from the Qiangtang Basin in Tibet, China. A high-precision geochronological framework was established by integrating U-Pb zircon dating with cyclostratigraphic tuning. Based on boron isotope analysis of brachiopod fossils, we reconstructed the seawater pH, which revealed a prominent negative excursion synchronous with the carbon isotope shift, providing robust evidence for ocean acidification during the ETE. Furthermore, uranium isotope data exhibit a negative excursion with a longer duration than that of boron isotopes, suggesting that marine anoxia persisted far beyond the interval of acidification. Our findings indicate that both ocean acidification and anoxia were direct drivers of the mass extinction; however, they played distinct roles: acidification primarily triggered the initial biotic crisis, whereas prolonged anoxia hindered the subsequent biotic recovery. The recurrence of coupled ocean acidification and anoxia, linked to global carbon cycle perturbations, represents a recurring mechanism for catastrophic ecological impacts throughout Earth's history.
How to cite: Wen, T., Fu, X., and Lu, T.: Ocean Acidification and Prolonged Anoxia during the End-Triassic Mass Extinction: Insights from the Qiangtang Basin, Eastern Tethys, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8933, https://doi.org/10.5194/egusphere-egu26-8933, 2026.
Tetrapod tracks record not only the morphological features of autopods but also critical insights into locomotion, behavior, and paleoecology. Since the behavior of extinct trackmakers cannot be observed directly, neoichnological experiments using extant analogues are essential for interpreting the fossil record.
In this study, we investigate the relationship between gait, substrate conditions, and track morphology, employing the red-eared slider (Trachemys scripta elegans) as a model organism. Controlled experiments were conducted across three size classes of trackmakers on various substrates with differing grain sizes and moisture levels. Tracks and trackways produced during distinct behaviors—including steady locomotion, pausing, climbing, and paddling—were documented and analyzed via high-resolution 3D digitization to extract quantitative morphological parameters.
Our results demonstrate that substrate moisture is the primary determinant of overall track morphology and preservation potential, with preservation quality exhibiting a hump-shaped relationship with increasing moisture content. While grain size primarily influences the resolution of fine anatomical details (e.g., digit and claw marks), dry or near-saturated substrates are prone to collapse or flow, resulting in shallow, poorly defined impressions. In contrast, moderately moist, fine-grained, and cohesive substrates are optimal for preserving clear outlines. Notably, very high-moisture or subaqueous tracks may partially recover detail upon drying. While track size correlates positively with body size on similar substrates, preservation quality is not strictly size-dependent: larger individuals produce clearer tracks on firm ground but may yield inconsistent results on loose sediments. Furthermore, behavioral variations induce distinct morphological signatures even under identical substrate conditions.
Comparison with fossil records suggests that Chelonipus parvus is inconsistent with turtle locomotion and should likely be reassigned to a non-turtle trackmaker, whereas Chelonipus liui shows greater affinity with Emydhipus. These findings provide experimental benchmarks for identifying turtle tracks and underscore the utility of neoichnological experiments in reconstructing ancient environments and vertebrate communities.
How to cite: Yin, H. and Xing, L.: Turtle tracks morphology: A neoichnological approach to fossil interpretation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17160, https://doi.org/10.5194/egusphere-egu26-17160, 2026.
Most natural paleoclimate archives are accretionary material presenting periodic structures that bear environmental and chronological information. Growth patterns of shells of marine bivalves also known as sclerochronology reflect changes in both biological and environmental factors and can potentially provide unique daily-resolved records of past environmental variability. Traditional methods of analyzing growth bands are time consuming and often face challenges in terms of accuracy and efficiency. To address these limitations, we introduce StripesCounter, an open access Python software designed for semi-automated banding detection and measurement. To test its effectiveness and determine whether shells of marine bivalves (Tridacna gigas) respond to rapid climate change, we analyzed daily growth variations in a modern specimen from Papua New Guinea (Hu-04-MT7), which experienced three major ENSO events during the 20th century. By using a laser scanning confocal microscope (LSCM) and the StripesCounter software, we counted and measured daily increments of shell growth. The results demonstrate a high degree of reproducibility and consistency compare to traditional manual counting methods. We used several detrending methods to subtract biological trends. Results show that, shell growth is sensitive to seasonal climatic variability caused by ENSO in this region. This can be observed in the semi-annual variability of the growth rate through a disturbance that can be attributed to a disruption in the semi-annual cycle of sea surface productivity and temperature. Our findings not only validate the method’s reliability for high temporal resolution studies but also enable the detection of subtle growth variations linked to environmental changes. This automated growth increment analysis can be extended to other archives with cyclic structures, including tree rings, corals, and other biogenic or abiotic laminated materials. StripesCounter offers a powerful and accessible tool for generating long high-resolution, temporally explicit datasets, opening new perspectives for investigating rapid environmental changes across diverse ecosystems and geological timescales.
How to cite: Brockmann, P., Boutreux, C., Elliot, M., Carré, M., and Gosselin, M.: StripesCounter: A new image software for increment measurement in paleoclimate archives , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21825, https://doi.org/10.5194/egusphere-egu26-21825, 2026.
Naturally acidified marine systems, such as volcanic vents, provide natural laboratories for examining ecological and taphonomy processes under conditions analogous to future ocean acidification. The Bottaro hydrothermal vent field off Panarea island in the Aeolian Archipelago (Italy) generates a short, meter-scale pH gradient in shallow waters (8–12 m; Goffredo et al., 2014). This study system provides a suitable setting for assessing how carbonate undersaturation affects macrobenthic community structure, shell production, and post-mortem preservation. We compared live-collected and associated dead-collected assemblages across four stations (four replicates per station) along the pH gradient. In total, ~3200 specimens representing 88 species were collected using a uniform sampling methodology. Diversity patterns were broadly concordant between live and dead assemblages. In both live and dead datasets, species richness declined toward lower pH (e.g., for dead-collected specimens, sample-standardized (n = 80) species richness was 20.9 species (CI 19.0-22.8) at the control site, and 11.9 (CI 6.7-11.7) at the vent site). Beta diversity, measured using the Betapart R package (Baselga & Orme, 2012), was primarily driven by species turnover (e.g., live dataset, β-bal = 0.55) rather than nestedness (β-gra = 0.32), consistent with changes in habitat structure, benthic vegetation cover, and pH decrease along the transect. Indeed, the most acidified station (pH ≤ 7.7) hosted a distinct, acid-tolerant community dominated by Alvania acida. Shell size, based on 50 randomly selected specimens, decreased significantly along the transect (e.g., dead shell median size 5.00 vs 1.75 mm in the control and most impacted site, respectively; Wilcoxon test < 0.01). This trend is consistent with dwarfism and shortened life spans under low-pH conditions. Multivariate taphonomy revealed intensified dissolution and a lack of encrustation at low-pH sites, and this pattern also affected living specimens, suggesting a very rapid rate of taphonomic processes. In addition, shell density and dead-live shell ratios both declined toward the vent indicating an increase in the rate of shell destruction in low-pH conditions. These results imply rapid carbonate loss and extremely short shell residence times, leading to high dead-live fidelity (i.e., high concordance in faunal composition and body size between live and dead assemblages). By integrating ecological and paleoecological evidence, this study illustrates how ocean acidification can reshape nearshore molluscan communities, alter their preservation pathways (hampering the reconstruction of baselines from paleoecological data), and reduce nearshore carbonate storage.
References:
Baselga, A. and Orme, D. 2012 Betapart: an R package for the study of beta diversity, Methods Ecol. Evol., 3, 808–812
Goffredo, S. et al. 2014. Biomineralization control related to population density under ocean acidification. Nature Climate Change 4, 593-597
How to cite: Scarponi, D., dos Santos, V., Mancuso, A., Goffredo, S., and Kowalewski, M.: Shells from Panarea vents (Italy): Acidification-driven carbonate loss reshapes benthic communities and the incipient fossil record, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10238, https://doi.org/10.5194/egusphere-egu26-10238, 2026.
Some biological organisms preserved in the sedimentary record are high-resolution archives that document environmental and ecological changes over time scales ranging from decades to millennia. Microcrustaceans, such as ostracods (Crustacea), are particularly notable in this context for their ability to preserve paleoecological information sensitive to environmental variations through their shells. The present study investigates the potential of ostracods as geoarchives in a small lagoon in southern Brazil, evaluating the processes that favor or limit their preservation in this environment. This research is based on analyzing seasonal collections of bottom sediments and sediment cores collected at six fixed points in the lagoon. Bottom collections were performed with a Van Veen dredge, and sediment cores were collected in 75-mm-diameter PVC tubes. So far, no preserved shells have been found in the core analyzed, which covers the first 40 cm. However, the ostracod species Cyprideis riograndensis and Perissocytheridea krummelbeini were found in bottom samples from this location. Nevertheless, previous studies from 1984 indicate that C. riograndensis was alive at the same point analyzed in this study. This raises questions because the results of ²¹⁰Pb dating suggest that the initial 40 cm of sediment dates back to the 1920s. This suggests that the species documented in the 1970s was not preserved in the sedimentary record despite its prior documentation. The absence of carapaces may be associated with dissolution caused by increased freshwater input, given that this evidence is closer to the river system. This phenomenon underscores how taphonomic processes can compromise fossil preservation and constitute a type of shifting baseline syndrome. Although the data obtained are partial, they reinforce the importance of taphonomy in paleobiology conservation studies and the integration of the fossil record, modern biota, chronological and sedimentary indicators, and historical data to understand past ecosystem dynamics.
How to cite: Soares de Moura, F. R. and do Nascimento Ritter, M.: How the differential preservation of ostracods (Crustacea) can obliterate records in conservation paleobiology studies, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4067, https://doi.org/10.5194/egusphere-egu26-4067, 2026.
Parasitism is one of the most successful life strategies among animals. The study of these interactions in the fossil record examines relationships between organisms and their environments, revealing how they are integrated into ecosystems and how they respond to climatic shifts and geological events. The late Quaternary is marked by pronounced climatic and ecological changes, and parasitism traces provide a means to investigate how these changes have influenced parasite-host interactions. The fossil record of parasites indicates an increase in occurrence and prevalence throughout the Phanerozoic, reaching its highest values in the Quaternary. In this context, studying such traces is essential for reconstructing parasite-host interactions in the fossil record. Despite its relevance and considerable interpretive potential, research on this interaction in the fossil record predominantly focuses on the Northern Hemisphere. This leaves a knowledge gap in the Southern Hemisphere, where quantitative studies integrating parasitism traces into their environmental context are scarce. The southern portion of the Coastal Plain of Rio Grande do Sul is one of the least-impacted coastal regions in Brazil, retaining near-pristine conditions. This area provides a valuable analogue for developing baseline scenarios. This study aims to assess the prevalence of parasitism using traces preserved in bivalves collected along the northern coast of Rio Grande do Sul, Brazil. To this end, we analyzed 744 mollusk shells collected from the foreshore, grouped into 27 samples and representing 15 bivalve species. Donax hanleyanus exhibited the highest relative frequency (88.7%) and was the only species bearing traces of a trematode parasite. The sampling universe for D. hanleyanus consists of at least 436 individuals, of which 261 display parasitic traces. The overall prevalence of parasitism in D. hanleyanus was 0.599 (CI 0.55–0.64), with a range of 0.238-0.800 across samples. The mean trace abundance per valve across samples was also estimated, ranging from 0.250 to 8.375. This overall prevalence is high compared with estimates for the nearshore setting of the highly anthropized Adriatic Sea coastal system (Italy), but it derives from a coastal sector that retains near-pristine conditions. Therefore, our estimates should be considered a baseline prevalence and trace-abundance range under low human impact. These results provide a quantitative basis for future comparisons to detect environmental degradation driven by coastal change, climate forcing, or increasing anthropogenic pressure, as indicated by shifts in parasite–host dynamics.
How to cite: Silva dos Santos, V., Scarponi, D., and do Nascimento Ritter, M.: Prevalence of trematode-induced traces in Donax hanleyanus from a near-pristine coastal region in southern Brazil, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19030, https://doi.org/10.5194/egusphere-egu26-19030, 2026.
Oceans absorb atmospheric CO2 depending on physicochemical exchanges and can act as sink or source for the atmospheric CO2. On a global scale, these source and sink zones vary both spatially and temporally. In the Pacific Ocean, the tropical zone is a strong source of CO2, whereas north and south subtropical zones are strong sinks. Atmospheric δ13C values (δ13Catm) have decreased over the last decades in response to the increase of the anthropogenic CO2 influx, also known as the Suess effect. The temporal reduction in δ13Catm has also been observed in dissolved inorganic carbon (δ13CDIC) due to the oceanic pump activity. Corals record environmental conditions by incorporating the ambient water trace elements and isotopes such as the δ13CDIC. Therefore, coral δ13C (δ13CC) can be used as an indicator of the past oceanic pump activity. In this study, we used previous temporal records of δ13CC Porites spp. corals, distributed across eighteen locations spread over subtropical and tropical areas of the Pacific Ocean. We added to this dataset a new record of δ13CC from Clipperton Island, a zone observed as a source zone. We created composite δ13CC record at Clipperton Island. We focused on long-term variability and investigated trends. Long-term trends are compared with the long-term trends of the sea-air CO2 fluxes from instrumental data period and with the long-term trend of reconstructed δ13Catm record from ice cores. General trends observed in all our selected records seems to follow the δ13Catm decreasing trend observed from ice core record. Meanwhile, we distinguished time breakpoint on each of our composites with different slopes at different timing. Time breakpoints seem to occur earlier, in records located within actual sink zones, whereas the change in slope occurred more recently in records originating from source zones. This study provides new insights into the spatial and temporal variability of the past oceanic pump activity.
How to cite: Raufauore, A., Malaizé, B., Hédouin, L., and Dassié, É. P.: Stacking coral δ13C records: spatial and temporal variability of the Pacific ocean’s carbon pump along the Anthropocene, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13535, https://doi.org/10.5194/egusphere-egu26-13535, 2026.
Shallow-marine shellfish communities in coastal regions are increasingly facing threats posed by ongoing environmental change, largely as a result of anthropogenic activities. The near-time geohistorical record offers opportunities to identify how these communities have responded in the past to episodes of environmental change that may have been triggered by similar ecological stressors, albeit of non-anthropogenic origin, thus providing longer term context to understanding the ecological health of modern ecosystems.
Shellbeds, high-density accumulations of shell remains, in a sedimentary sequence often represent perturbations of the “usual” environmental conditions under which sediments accumulated. Shellbeds can vary in thickness, spatial geometry, species composition, internal structure, and fidelity of shell preservation reflecting the complex processes that are often involved in their formation, for example via sedimentological processes including storm events and current winnowing. Alternatively, shellbeds can form as in situ biogenic accumulations. Identifying the processes responsible for the formation of shellbeds offers insight into the local ecological, physical, and environmental conditions at the time of their formation.
The results of a study of Holocene, (~9-3kyr) shellbeds that occur in the subsurface of Galway Bay, Western Ireland are presented. X-ray imaging of the cores indicates the spatial extent of the shellbeds extends across most of Galway Bay, ~450km2. Regional-scale observations suggest a variation in the shellbed biofacies from easterly bivalve-dominated shellbeds to westerly near mono-specific Turritella-dominated shellbeds. A chronostratigraphic framework using radiocarbon dating reveals the bivalve-dominated shellbeds predate the Turritella-dominated shellbeds by ~1500 years, with formation of the Turritella-dominated shellbeds occurring ~7-4kyr. Vertical stacking of the latter on the former locally is consistent with this and is attributed as a response to a Holocene transgression in Galway Bay.
The bivalve-dominated shellbeds are similar in composition and taphonomy to extant populations identifiable from samples currently collected from Galway Bay. Various taphonomic criteria identify the Turritella-dominated shellbeds as in situ communities, contemporaneous across Galway Bay, for which no modern analogue has been identified in the bay. These near monospecific populations represent a widespread event lasting ~3000 years, that developed rapidly and simultaneously across Galway Bay for a sustained period before terminating abruptly. This event was followed by re-establishment of the bivalve-dominated communities typical of nearshore modern Galway Bay.
Holocene in age Turritella-dominated shellbeds in NE Europe have been attributed as a response to the 8.2kyr event. Their being younger excludes this origin for the Galway Bay Turritella shellbeds suggesting they are an ecological response to a different episode of environmental change. Formation of these Turritella shellbeds is attributed to a set of environmental conditions that favoured development of an opportunistic community during the very Late Holocene transgression of Galway Bay.
Future lipid biomarker and trace element analysis will elucidate these subtle changes in environmental conditions under which the shellbeds formed . This will confirm the potential of shellbeds as an indicator of the sensitivity of these shallow-marine ecosystems to environmental variations, and a predictor of the future for these shell communities as their ecosystems continue to come under increasing environmental stress from anthropogenic activities.
How to cite: Healy, R., Orr, P., Benetti, S., Haughton, P., O'Beirn, F., Healy, L., and Holmes, A.: Condensed shellbeds record drastic ecological shifts during the late Holocene; A multiproxy study from Galway Bay, Western Ireland. , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19458, https://doi.org/10.5194/egusphere-egu26-19458, 2026.
Marine fossil assemblages typically include remains of non-contemporaneous organisms that accumulated over time or were subsequently mixed by bioturbation or reworking. The resulting time averaging (temporal mixing) imposes the fundamental limit on the temporal resolution of paleontological samples and thus restricts the range of processes that can be studied in the fossil record. Over the last decades, numerous case studies have estimated time averaging based on post-mortem age distributions of individually-dated skeletal remains preserved in late Quaternary sediments. However, the limited scope of previous studies constrains our understanding of the variation in temporal resolution of paleontological samples across different taxa and depositional settings, and factors controlling it.
Here, we present a global compilation of data from multiple projects focused on age-dating of marine invertebrate remains sampled from present-day seabeds and Quaternary sediment cores. The dataset aggregates radiocarbon and amino-acid racemization ages of skeletal elements and links them to a broad range of standardized variables describing sampling methodology, intrinsic characteristics of skeletal producers, as well as stratigraphic, sedimentary and environmental context. Currently, the dataset includes postmortem age estimates for over 7,500 specimens representing 383 monospecific collections of 10 or more individually dated specimens coming from 291 sampling units (core increments, grabs, dredges, hand collections or suction samples). The sampling locations range from nearshore to continental slope settings in seven warm-temperate, subtropical, and tropical regions.
Preliminary analyses suggest that the majority of the analyzed samples underwent multi-centennial to supra-millennial time averaging, although a significant portion of them (14-23% depending on the age dispersion measure) was time-averaged to less than 100 years. The dataset is strongly dominated by aragonitic bivalves (>80% of samples and dated specimens), with much more limited data available for other mollusk taxa, brachiopods and echinoids. Outer shelf and slope environments are also poorly represented with only 7% of the sampling sites coming from water depths below 100 m. Our compilation highlights the lack or relative paucity of quantitative time-averaging estimates from deep-water and high-latitude settings, as well as for taxa with low durability or multi-elemental skeletons (such as echinoderms and arthropods). Increasing the taxonomic and environmental coverage of the data is thus crucial for improving our current understanding of the temporal resolution of the fossil record.
How to cite: Nawrot, R., Kowalewski, M., Tomašových, A., Scarponi, D., Zuschin, M., and Kosnik, M. A.: Quantifying the limits of paleontological resolution using a global compilation of individually-dated skeletal remains, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-23018, https://doi.org/10.5194/egusphere-egu26-23018, 2026.
Late Quaternary megafaunal extinctions in North America represent a major loss of large-bodied mammals, yet the ecological processes underlying species-specific decline remain unclear. In particular, the role of short-term habitat changes during the last deglaciation has received less attention than climatic or anthropogenic explanations. Palaeoecological studies indicate that mid-latitude North America experienced extensive but short-lived wetland expansion during the Bølling–Allerød interstadial (~14.6–12.8 ka), driven by meltwater discharge from the retreating Laurentide Ice Sheet, followed by rapid wetland contraction around the onset of the Younger Dryas. In this study, we examine how these wetland changes as major habitats are reflected in megafaunal distribution patterns across the Bølling–Allerød to Younger Dryas transition. We compile genus-level fossil occurrence data from publicly available databases and integrate them with spatial reconstructions of deglacial wetland extent. Using time-sliced analyses between approximately 15 and 11 ka, we explore changes in geographic range, spatial clustering, and distributional fragmentation of megafaunal taxa. Our analyses focus on wetland-associated taxa such as Mammut (mastodon), Castoroides (giant beaver), and Cervalces (stag-moose), and compare their spatiotemporal distribution patterns with those of non-wetland-associated megafauna. Preliminary results show that wetland-associated taxa tend to display more spatially clustered and persistent distributions during the Bølling–Allerød, when wetland extent was greatest. Following the onset of the Younger Dryas, these taxa exhibit increased fragmentation and range contraction. In contrast, non-wetland-associated taxa show weaker and less consistent changes through time. These results suggest that transient wetland landscapes were closely linked to short-term distributional stability in certain megafauna prior to rapid decline, and motivate further analyses to better evaluate habitat-related mechanisms during the last deglaciation.
How to cite: Choe, Y. and Byun, E.: Potential Impacts of Transitional Wetland Habitats on Megafaunal Distributions in North America during the Last Deglaciation , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8869, https://doi.org/10.5194/egusphere-egu26-8869, 2026.
Most studies evaluating shifts in community composition in response to environmental change focus on taxonomic diversity, while functional diversity remains underexplored, particularly in marine ecosystems, despite its relevance to ecosystem functioning. We evaluated shifts in the functional diversity of molluscan nearshore communities in the Adriatic Sea (Italy) in response to late Quaternary climate change. We applied biological traits analysis (BTA) based on a broad range of life history, behavioral, and morphological characteristics to assess these changes.
Previous research by Scarponi et al. (2022) has shown that molluscan nearshore metacommunities in the northern and central Adriatic exhibited a resilient response to large-scale climatic and sea-level fluctuations of the late Quaternary. Taxonomic composition was very similar between the last (Thyrrenian) and the present interglacial (Holocene) but shifted to a different state during the last glacial. We studied the same dataset to test whether glacial assemblages also exhibited distinct functional composition compared to their interglacial counterparts. For this purpose, we applied fuzzy correspondence analysis (FCA, Chevenet et al., 1994). Differences in functional composition were further explored using functional beta diversity (Villéger et al., 2013) between assemblages of the different time intervals. Furthermore, we evaluated changes in functional alpha diversity based on multidimensional functional space (Laliberté & Legendre, 2010).
The results of FCA and beta diversity analysis demonstrate that functional composition was different during the last glacial, whereas it was similar for the two interglacials. Traits that differ most strongly between the glacial and interglacials are attachment type and feeding guild. In addition to differences in composition, functional diversity was higher during the last glacial, when accounted for sample size, which confirms expectations based on the higher taxonomic diversity during that time documented by Scarponi et al. (2022). Our results provide valuable insights into the natural range of variability in functional diversity of nearshore communities in the Adriatic Sea during major shifts in climate and sea level, demonstrating that taxonomic turnover also affected functional composition of assemblages.
References
Chevenet, Fran., Doléadec, S., & Chessel, D. (1994). A fuzzy coding approach for the analysis of long-term ecological data. Freshwater Biology, 31(3), 295–309. DOI: 10.1111/j.1365-2427.1994.tb01742.x
Laliberté, E., & Legendre, P. (2010). A distance‐based framework for measuring functional diversity from multiple traits. Ecology, 91(1), 299–305. DOI: 10.1890/08-2244.1
Scarponi, D., Nawrot, R., Azzarone, M., Pellegrini, C., Gamberi, F., Trincardi, F., & Kowalewski, M. (2022). Resilient biotic response to long-term climate change in the Adriatic Sea. Global Change Biology, 28(13), 4041–4053. DOI: 10.1111/gcb.16168
Villéger, S., Grenouillet, G., & Brosse, S. (2013). Decomposing functional β-diversity reveals that low functional β-diversity is driven by low functional turnover in European fish assemblages: Decomposing functional β-diversity. Global Ecology and Biogeography, 22(6), 671–681. DOI: 10.1111/geb.12021
How to cite: Schweigl, L., Nawrot, R., Kowalewski, M., Pittala, V., and Scarponi, D.: Effects of long-term climate change on the functional diversity of molluscan assemblages in the Adriatic Sea, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4962, https://doi.org/10.5194/egusphere-egu26-4962, 2026.
The Mediterranean Sea is a semi-enclosed basin hosting more than 7% of global marine biodiversity. It is among the areas most exposed to human pressure and climate change. The study of the pristine status of ecosystems and marine shallow habitats can be used as a reference for evaluating current human-derived impacts. The Last Interglacial (LIG, ~129 to 116 ka ago) was a warm time interval that could be considered a modern analogue lacking an anthropogenic fingerprint and represents a useful scenario for future climate change. It can be used to reconstruct key environmental variables sustaining non-anthropically modified Mediterranean shallow-water ecosystems under warm climate. Traces of past climatic features are indeed recorded in some biotic archives, whose geochemical properties record seawater parameters. For instance, the bivalve Pinna nobilis (Linnaeus, 1758) and the coral Cladocora caespitosa (Linnaeus, 1767) are endemic to the Mediterranean Sea and their stable oxygen isotope and trace element compositions are useful proxies to reconstruct the paleoclimate, potentially tracing the history of the Mediterranean Sea from the Pliocene to the present. In this study, we investigated climatic proxies in fossil specimens of C. caespitosa and P. nobilis from Last Interglacial (LIG) marine-terrace deposits in the Taranto area (Puglia, Italy), in order to reconstruct paleo–seawater temperatures during the organisms’ lifetimes. We performed X-ray imaging on the coral to investigate the alternation of annual density bands. The annual growth pattern was used as a guide to cut corallites with a dental drill, allowing the preparation of samples at sub-annual resolution for geochemical analyses. A drill was used to collect calcite powder sub-samples from fossils of P. nobilis at ~1 mm resolution following the correct growth sequence. Subsequently, geochemical analyses were carried out on trace elements in the C. caespitosa aragonite and on the oxygen stable isotope ratio (δ18O) in the P. nobilis calcite. The aim of this work was to reconstruct paleotemperatures of the Last Interglacial period with an annual or sub-annual resolution, comparing our results with present-day temperature records to better define a LIG climate scenario.
How to cite: Logrieco, A., Regattieri, E., Cornacchia, I., Montagna, P., Douville, E., Causio, S., Caldara, M. A., Chimienti, G., and De Santis, V.: Cladocora caespitosa and Pinna nobilis: useful climatic archives to reconstruct Last Interglacial paleotemperatures, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19836, https://doi.org/10.5194/egusphere-egu26-19836, 2026.
The Middle Pleistocene locality of Ponte Molle is one of the most important sites of Rome in terms of the number of fossil remains (Iannucci et al., 2023). The locality was exploited for gravel quarrying activities from the 1800s to the early 1900s, resulting in the recovery of a diverse and abundant collection of fossil mammals. Stratigraphic and historical evidence agree in interpreting the Ponte Molle fauna as having been recovered from the lower gravelly level of the Valle Giulia Formation (MIS 13, ca. 500 ka) (Mecozzi et al., 2021). The faunal assemblage includes numerous remains of common species such as Palaeoloxodon antiquus, Bos primigenius, and Cervus elaphus, as well as documenting the presence of more elusive taxa in the early Middle Pleistocene of Europe, such as Sus scrofa, Castor fiber, and Crocuta crocuta (Mecozzi et al., 2021).
This study applies stable isotope analysis (δ¹³C and δ¹⁸O) to the enamel of 29 teeth (12 equids, Equus mosbachensis and 17 cervids, Cervus elaphus and Dama clactoniana), part of the historical collection from Ponte Molle, in order to reconstruct dietary patterns and infer local habitat variability. Carbon isotope ratios (δ¹³C) range from –14.55‰ to –11.61‰ (VPDB), indicating a diet dominated by C3 vegetation and suggesting temperate woodland to open forest environments. The values obtained for cervids indicate a large interspecific overlap, while differences emerge with respect to equids. Equids exhibit slightly higher mean δ¹³C values (–11.06‰; SD = 0.4) than cervids (Cervus elaphus –12.08‰, SD = 1.3; Dama clactoniana –11.69‰, SD = 1.2), consistent with more open foraging areas; the difference between the mean values of Equus mosbachensis and Cervus elaphus is statistically significant (p<0.05). Oxygen isotope values (δ¹⁸O) range from –6.51‰ and –4.01‰ (VPDB), suggesting variability in water sources. In this case, the difference between mean values is not statistically significant suggesting that the relatively wide range of oxygen isotope values may be related to local hydrological conditions. These results contribute to refining palaeoecological models for central Italy during MIS 13 and highlight the potential of herbivore isotopic signatures as proxies for reconstructing Middle Pleistocene ecosystems. This work has been supported by the Italian Ministry of University and Research, PRIN 2022 scorrimento – Prot. 2022JWFEKE “The evolution of mammals in changing ecosystems of the Middle Pleistocene of Italy”.
References
Iannucci A., Conti J., Curcio F., Iurini D.A., Mancini M., Mecozzi B., Strani F., Sardella R. (2023). Middle Pleistocene mammal faunas of the area of Rome: recent results and ongoing work on the MUST collection. Journal of Mediterranean Earth Sciences 15, 19–37.
Mecozzi B., Iannucci A., Mancini M., Sardella R. (2021). Redefining Ponte Molle (Rome, central Italy): an important locality for Middle Pleistocene mammal assemblages of Europe. Alpine and Mediterranean Quaternary, 34, 131–154.
How to cite: Giustini, F., Brilli, M., Iannucci, A., and Sardella, R.: Stable isotope analysis of cervids and equids teeth enamel as a proxy for paleoenvironmental reconstruction at the early Middle Pleistocene site of Ponte Molle (Rome, central Italy), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13051, https://doi.org/10.5194/egusphere-egu26-13051, 2026.
Mass extinctions have played a crucial role in shaping the biogeographic structure of the marine biota throughout the Phanerozoic. Multiple clades exhibited pronounced cosmopolitanism following the Permian-Triassic (P/T) and Triassic-Jurassic (T/J) mass extinctions, characterized by sharp increases in biogeographic connectedness (BC). Here, we analyze global occurrence data of bivalves to examine their biogeographic dynamics across the Cretaceous-Paleogene (K/Pg) mass extinction boundary. In striking contrast to the patterns observed during the P/T and the T/J events, BC declines significantly from the Maastrichtian (0.049 ± 0.002) to the Danian (0.024 ± 0.002), signaling a shift toward heightened provincialism. Although geographically widespread genera exhibited selective survival through the K/Pg crisis, these survivors underwent substantial range contraction across the boundary, resulting in a fragmented post-extinction bivalve biogeography dominated by geographically narrow-ranging taxa. Quantitative comparisons across the P/T, T/J, and the K/Pg mass extinctions indicate that Maastrichtian genera possessed markedly lower within-genus species richness across the localities, compared to pre-P/T (Changhsingian) or pre-T/J (Rhaetian) levels, which might had limited species-level buffering of geographic ranges of genera, preventing the cosmopolitanism events seen after earlier events. Our findings highlight how taxonomic structure within clades influences biogeographic resilience, with implications for understanding macroevolutionary consequences of mass extinctions.
How to cite: Mukhopadhyay, A. and Paul, S.: Provincialism of bivalves across the K/Pg mass extinction boundary, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10494, https://doi.org/10.5194/egusphere-egu26-10494, 2026.
The size structure of macrobenthic assemblages exhibits a major shift across the Pliensbachian/Toarcian boundary event on the NW European shelf, with the appearance of common micromorphic brachiopods (Koninckella community). This community type then abruptly disappears near the base of the main negative carbon isotope excursion associated with the Toarcian Oceanic Anoxic Event. Several studies documented that micromorphic brachiopods become common already in the Spinatum Zone in the NW Algeria (Traras Mountains) or in Tunisia (Jebel Zaghouan), indicating that the community shift took place earlier on the southern Tethyan margin. Therefore, to assess temporal changes in the composition and size structure of macrofaunal community on the southern Tethyan margin, we investigated a Pliensbachian-Toarcian succession in the Beni Snassen Mountains. New chemostratigraphic data document the presence of the initial negative carbon isotope excursion at the Pliensbachian/Toarcian boundary, with δ13C declining from -24.5 to‰ -26‰ just at the base of a marl that overlies the Beni Hammad Formation. δ13C values decline to -23.5‰ in the middle part of the Beni Amyir Formation, and abruptly decline to -26‰ and -27‰ just in the uppermost part of the Beni Amyir Formation, documenting the onset of the main negative carbon isotope excursion. We find that koninckinid brachiopods and Nannirhynchia become common and appear already in the Spinatum Zone where they co-occur with larger brachiopods (Prionorhynchia, Phymatothyris, Cisnerospira), similarly as in Algeria and Tunisia. Interestingly, in the lowermost Toarcian (Polymorphum Zone), the assemblage of micromorphic brachiopods is more diverse than in the Lusitanian Basin. With the exception of Nannirhynchia, all micromorphic genera went extinct near the onset of the main carbon isotope excursion. This work was supported by the Slovak Research and Development Agency (APVV22-0523).
How to cite: Tomašových, A., Boudchiche, L., Chennouf, R., Sadki, D., and Schlögl, J.: Evaluating the decline in size of brachiopod assemblages during the Pliensbachian/Toarcian boundary event (Eastern Morocco), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13784, https://doi.org/10.5194/egusphere-egu26-13784, 2026.
The preservation of soft tissue–like structures in fossil vertebrate bones has been increasingly reported over the past two decades, yet their origin and preservation mechanisms remain debated. In this study, we investigated a fragment of theropod dinosaur bone using a multi-method microscopic and analytical approach to assess the nature, composition, and taphonomic context of structures morphologically resembling original soft tissues.
Optical microscopy and scanning electron microscopy (SEM) revealed abundant vessel-like structures characterized by tubular morphologies and fibrous wall architectures, as well as osteocyte-shaped lacunae with preserved canalicular networks. Energy-dispersive X-ray spectroscopy (EDS) demonstrated that many of these structures are permineralized predominantly by iron oxides, consistent with models proposing iron-mediated stabilization of organic substrates through early diagenetic mineral coatings. In addition, localized calcium fluoride mineralization was identified within some vascular casts, indicating chemically heterogeneous microenvironments and suggesting post-depositional fluid interactions. The occurrence of framboidal pyrite further points to transient anoxic conditions associated with organic-rich microdomains during early fossilization.
Histochemical staining revealed the presence of fungal hyphae and spores within some amorphous, gelatinous structures, indicating secondary microbial colonization of the bone. Two distinct fungal morphotypes were observed; however, not all translucent and elastic structures exhibited fungal staining. Importantly, confocal laser scanning microscopy combined with protein-specific fluorescent probes detected proteinaceous material selectively associated with vessel-like structures, while fungal elements showed distinct staining patterns. This spatially resolved signal supports the presence of endogenous protein remnants, likely representing degraded collagen or collagen-derived compounds, rather than purely microbial biofilms.
Together, these results demonstrate that fossil bone can preserve a complex assemblage of original biological residues, diagenetic mineral phases, and later microbial overprints. Iron-rich mineralization appears to play a critical role in the long-term stabilization of soft tissue–derived structures, while localized geochemical conditions govern the diversity of preservation pathways. Our findings contribute to a growing framework of molecular taphonomy and highlight the importance of integrated morphological, chemical, and biochemical analyses in evaluating claims of soft tissue preservation in deep time.
How to cite: Staniek, A. and Surmik, D.: Iron-mediated mineralization and microbial overprints in soft tissue–like structures from a theropod dinosaur bone, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14592, https://doi.org/10.5194/egusphere-egu26-14592, 2026.
Posters virtual: Tue, 5 May, 14:00–18:00 | vPoster spot 3
EGU26-12124 | Posters virtual | VPS26
Seasonal variability at the onset of the Late Palaeozoic Ice Age: insights from Gigantoproductus shellsTue, 05 May, 14:36–14:39 (CEST) vPoster spot 3
Understanding transformations of the climate system in the geological past is essential for predicting and mitigating the effects of global climate change in the next future. The geological record provides a unique archive that documents long-term fluctuations of environmental variables, including seasonality. Seasonality appears to have played a crucial role in extreme climate transitions, highlighting the importance of constraining its variability in the past. Increased seasonality is often associated with colder conditions and the development of ice accumulations, making it a key parameter for understanding and forecasting climate change.
Species of the brachiopod Gigantoproductus are giants within the Palaeozoic sedentary benthos, characterised by exceptional size and thick shells, reaching over 30 cm in width and more than 1 cm in shell thickness. These features make them unparalleled bioarchives for palaeoecological and palaeoclimatic reconstructions, enabling the investigation of long-term changes during key intervals of past climate change.
In this study, specimens of Gigantoproductus semiglobosus from upper Visean (Mississippian, Carboniferous) successions of western Ireland (Aran Islands and the Burren) were subjected to detailed diagenetic screening and subsequently analysed using a sclerochemical approach (δ18O, δ13C). These analyses were used to reconstruct seasonal variability and to provide additional evidence for the timing of Mississippian phases of the Late Palaeozoic Ice Age (LPIA).
Our results show that δ18O profiles from well-preserved shells record high seasonal variations (Δδ18O = 0.9 to 1.9 ‰ corresponding to a ΔT = 4 to 11 °C) for palaeoequatorial settings, as also observed in coeval species of Gigantoproductus from the UK (Angiolini et al., 2019). This seasonal variation is much higher than that recorded in comparable shallow water, low latitude environments both nowadays and in the distant past. The pronounced seasonality recorded by several species of Gigantoproductus from western Ireland and the UK at low palaeolatitudes supports the onset of a sustained Gondwanan glaciation in the late Visean. Also, the palaeogeographic distribution of the species of Gigantoproductus and the geochemical composition of their shells indicate that low-latitude Mississippian ocean waters did not experience a temperature decrease at the onset of the Gondwanan glaciation, but rather a marked increase in seasonal variability.
Overall, this study highlights the importance of resolving long-term changes in seasonality, using fossil carbonate shells as palaeoclimatic archives during different intervals of climate change, in both the recent and distant past, to better understand and predict long-term transformations of the climate system.
References
Angiolini et al. (2019). The giants of the phylum Brachiopoda: a matter of diet? Palaeontology, Vol. 62, Part 6, pp. 889–917
How to cite: Crippa, G., Angiolini, L., Azmy, K., Cannaò, E., Doyle, E., Della Porta, G., Murray, J., O’Connell, M., Viaretti, M., and Harper, D. A. T.: Seasonal variability at the onset of the Late Palaeozoic Ice Age: insights from Gigantoproductus shells, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12124, https://doi.org/10.5194/egusphere-egu26-12124, 2026.
EGU26-455 | ECS | Posters virtual | VPS26
Ecological and hydrological reconstruction of the western Indian coastal ocean during the Early Miocene (Burdigalian) based on the oxygen and carbon isotopes of multiple ostracod species.Tue, 05 May, 15:00–15:03 (CEST) vPoster spot 3
Calcareous valves of various ostracod species from the Miocene (Burdigalian) Quilon Formation, Kerala Basin, southwest India, were separated and identified up to the species level. The 15 most abundant species were selected to determine the carbon and oxygen isotope composition, with 2 to 5 replicates to assess the variation among individual valves within each species. The δ¹³C ratios range from 0.56 to -4.65‰ VPDB with a standard deviation range between 0.08 to 0.53‰. The δ¹⁸O ratios varied between -2.57 to -4.25‰ VPDB with a standard deviation between 0.12‰ and 0.46‰. The seawater δ¹⁸O values were calculated using the empirical equation by Kim and Neil (1997), and they range between -3.08‰ to -0.01‰ (VSMOW), with an average of -1.85‰ (VSMOW). This study also tries to categorise the species into distinct habitat groups, namely the open ocean, mixed estuarine and shallow-marine environment with significant coastal upwelling influence, based on their isotopic composition. The results were compared with the habitats of their extant relatives at the family and genus levels, as well as information derived from valve ornamentations. Ostracods, namely Phlyctenophora meridionalis, Paranesidea cf. gajensis, Bairdoppilata sp., and Krithe autochthona inhabited a range of settings from shallow to deeper marine environments. The species Aurila singhi, Paractinocythereis gujaratensis, Stigmatocythere sp., Actinocythereis sp., Trachyleberis sp., Neocyprideis murudensis, Pokornyella chaasraensis, and Tenedocythere keralaensis are identified to inhabit an estuarine or shallow-marine environment influenced by freshwater influx. Whereas Paijenborchellina prona, Cytherelloidea sp., and Loxoconcha confinis show an indication of a shallow-marine environment with significant coastal upwelling influence.
How to cite: m s, A., kannan, P., and V Kapur, V.: Ecological and hydrological reconstruction of the western Indian coastal ocean during the Early Miocene (Burdigalian) based on the oxygen and carbon isotopes of multiple ostracod species., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-455, https://doi.org/10.5194/egusphere-egu26-455, 2026.
