Recently, an international research team including Prof. CAI Chenyang (Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences) and Erik Tihelka (joint-training PhD student, University of Cambridge), together with collaborators from the United States, Spain and other countries, reported a new stem‑group insect, Chosha praecursor Tihelka, Engel & Cai, 2026 (Fig. 1), from the Late Mississippian (~324 Ma) of Texas, USA. The team also investigated enigmatic stem‑insect material from the Early Devonian chert biota of Britain and the Late Carboniferous Mazon Creek biota of the United States (Fig. 2). These insect fossils fill critical gaps in early insect evolution, revise long‑standing interpretations of insect body-plan transformation and pancrustacean terrestrialization, and furnish key empirical evidence for the gradual aquatic‑to‑terrestrial evolutionary transition of insects. The findings were published online 26 August 2026 in Nature.The establishment of complex terrestrial ecosystems represents a milestone innovation in the evolutionary history of life on Earth. It marks the definitive release of organisms from marine constraints and inaugurates a brand-new phase for the diversification of terrestrial biota. Evidence from molecular‑clock estimates, trace fossils and exceptional‑preservation biotas indicates that the terrestrialization of arthropods stretches back to the Cambrian‑Ordovician, far earlier than inferred from conventional body-fossil records. As the most species‑rich animal group on our planet, insects have long posed major gaps in research regarding their early origins and the evolutionary transition to land.Paleontology has long grappled with the well-known hexapod gap. Molecular‑clock reconstructions suggest that hexapods diverged from marine crustacean relatives and initiated terrestrial adaptation as early as the Cambrian‑Ordovician. However, globally undisputed hexapod body fossils are only documented from the Early Devonian Rhynie Chert (ca. 405 Ma), and unambiguous insect fossils do not occur in abundance until the Late Carboniferous. This creates an 80-million-year gap in the fossil record. Moreover, direct fossil evidence documenting how early insects gradually adapted to terrestrial habitats from aquatic and semi‑aquatic settings, as well as the transformation of their body plans, has remained scarce. Consequently, evolutionary pathways, morphological innovations and ecological adaptive mechanisms underlying insect terrestrialization have remained poorly constrained.Recently, an international research team including Prof. CAI Chenyang (Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences) and Erik Tihelka (joint-training PhD student, University of Cambridge), together with collaborators from the United States, Spain and other countries, reported a new stem‑group insect, Chosha praecursor Tihelka, Engel & Cai, 2026 (Fig. 1), from the Late Mississippian (~324 Ma) of Texas, USA. The team also investigated enigmatic stem‑insect material from the Early Devonian chert biota of Britain and the Late Carboniferous Mazon Creek biota of the United States (Fig. 2). These insect fossils fill critical gaps in early insect evolution, revise long‑standing interpretations of insect body-plan transformation and pancrustacean terrestrialization, and furnish key empirical evidence for the gradual aquatic‑to‑terrestrial evolutionary transition of insects. The findings were published online 26 August 2026 in Nature.Fossils of Chosha praecursor derive from calcareous claystone concretions within the Tesnus Formation of the Marathon Uplift, western Texas, and exhibit exquisite, well‑preserved anatomical details. Using cross-polarized light imaging, the team resolved its distinctive morphological traits and corrected long‑standing misinterpretations that these specimens represented crustacean larvae. The studied material corresponds to adult females with a body length of 32.09 mm; a median caudal filament plus two cerci extend the total length to 49.66 mm. The fusiform body displays derived traits diagnostic of hexapods and insects, while retaining plesiomorphic ancestral features (Fig. 1).Systematic analyses demonstrate that Chosha praecursor possesses hallmark insect structures including an ovipositor and terminal caudal filament. Its thorax bears a segmented trunk and six walking legs, conforming to the canonical insect body plan. Most strikingly, however, segments 1‑9 of the abdomen bear segmented appendages; posterior abdominal limbs are modified into paddle‑like structures — a morphology unknown among extant crown‑group insects (Fig. 1). Palaeoenvironmental reconstructions indicate that the host strata represent near‑shore shallow‑water delta‑coastal settings, confirming that this early stem‑insect led a semi‑aquatic, amphibious lifestyle, occupying humid microhabitats across aquatic‑terrestrial interfaces.Based on detailed comparative morphology and phylogenetic analyses, the researchers re‑evaluated three enigmatic Palaeozoic hexapod fossils: Leverhulmia from the Early Devonian of Scotland, and an unnamed hexapod from the Mazon Creek biota, USA. Phylogenetic results recover Chosha praecursor together with these taxa as a primitive insect stem clade. Representing the oldest documented insect assemblage globally, this clade substantially connects the evolutionary genealogy of early insects (Fig. 3).This study delivers paradigm-shifting scientific advances that reshape our framework for understanding insect terrestrial evolution. First, it fills the long‑persistent 80‑million‑year hexapod gap. Reliable evidence for insect origins and early diversification is pushed back from the Late Carboniferous into the Early Devonian, reconciling to some degree discrepancies between molecular‑clock estimates and the body-fossil record. Prior models assumed that insects evolved fully terrestrial body plans immediately following land colonization. The paddle‑shaped abdominal appendages and amphibious habit demonstrated here prove that insect terrestrialization was not an abrupt leap, but unfolded via a prolonged semi-aquatic amphibious transitional phase (Fig. 4).Second, the fossils illuminate pivotal transformations in the insect body plan. Extant hexapods retain only six thoracic legs; abdominal appendages are almost entirely lost. By contrast, Palaeozoic stem-insects commonly preserve segmented abdominal limbs. This confirms that reduction of abdominal appendages constituted a key evolutionary innovation for terrestrial adaptation. These structures were progressively simplified and lost from the swimming appendages of crustacean ancestors, ultimately yielding the body organization seen in modern insects. The findings clarify the morphological transition from pancrustacean ancestors to hexapod insects (Figs 1, 4). Furthermore, the plesiomorphic ovipositor preserved in Chosha praecursor demonstrates that early insects already possessed diverse oviposition adaptations, providing the structural foundation for subsequent colonization of heterogeneous terrestrial microhabitats and later insect radiations.In addition, the research reconstructs ecological scenarios for early insects. Stem-group insects combined aquatic locomotor and respiratory adaptations with terrestrial body architectures. Their diets likely included humus, plant detritus and fungal spores. Early insects thus fulfilled multifunctional ecological roles as decomposers and consumers within aquatic‑terrestrial ecotones, acting as pivotal components driving the maturation of Palaeozoic terrestrial ecosystems (Figs 2, 4).Fossils of Chosha praecursor and related Palaeozoic stem-insects reconstruct the early terrestrialization trajectory of Earth’s most species‑rich animal group, revising interpretations of body-size evolution, ecological adaptation and co‑evolution with terrestrial ecosystems. Terrestrial colonization by insects was a gradual process; retention, remodelling and reduction of ancestral aquatic structures permeated their early evolutionary history. An amphibious transitional phase formed the critical evolutionary bedrock enabling insects to conquer land. These results supply invaluable fossil evidence for deciphering hexapod origins and body‑plan evolution, and offer fresh perspectives on the origin and early diversification of complex terrestrial ecosystems on Earth.This research was supported by the National Key Research and Development Program of China and the National Natural Science Foundation of China. Mr. Chao Tan prepared the palaeoecological reconstructions.Reference: Tihelka E., Vásquez C., Engel M.S., Schram F.R., Lozano‑Fernandez J., Cai C., 2026. Amphibious stem‑insect sheds light on colonization of land. Nature. https://doi.org/10.1038/s41586‑026‑10961‑2. Fig. 1 The stem-group insect Chosha praecursor Tihelka, Engel & Cai, 2026 from the Carboniferous Tesnus Formation (ca. 324 Ma), Texas, USA.Fig. 2 Comparative anatomical details of stem-insects and extant apterygote insects.Fig. 3 Phylogeny of early hexapods and the evolution of key morphological traits.Fig. 4 Palaeoecological reconstruction of the Carboniferous stem-insect Chosha praecursor.
Recently, XUE Yan, a PhD candidate at the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), working under the supervision of Professors ZHENG Daran and LI Gang and collaborating with Professor JING Zhenhua from the Chengdu University of Technology, conducted a multi-proxy geochemical investigation on the Jiufengshan Formation at the Shiyoukuangtun section in the Dayangshu Basin, eastern Inner Mongolia. Along with systematic paleontological and comprehensive stratigraphical work, this study integrated stable organic carbon isotope analyses, Rock-Eval pyrolysis, iron speciation, and redox-sensitive trace-element geochemistry to reconstruct the lake ecosystem and bottom-water conditions that prevailed when the Jehol Biota inhabited the basin. It further examined the relationship between organic-matter enrichment and fossil preservation. The results were published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology.The Jehol Biota is one of the most representative Cretaceous terrestrial biotas, and provides an important window into the evolution of terrestrial ecosystems. Previous paleoenvironmental reconstructions on the Jehol Biota have focused mainly on its core distribution region in northern Hebei and western Liaoning, while non-core distribution regions remain poorly studied. The organic-rich shales of the Lower Cretaceous Jiufengshan Formation in the northern Great Xing’an Range yield abundant fossils, providing a valuable archive for elucidating the palaeoenvironmental mechanisms that promoted the flourishing and preservation of the Jehol Biota, as well as the evolution of Early Cretaceous lacustrine ecosystems.Recently, XUE Yan, a PhD candidate at the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), working under the supervision of Professors ZHENG Daran and LI Gang and collaborating with Professor JING Zhenhua from the Chengdu University of Technology, conducted a multi-proxy geochemical investigation on the Jiufengshan Formation at the Shiyoukuangtun section in the Dayangshu Basin, eastern Inner Mongolia. Along with systematic paleontological and comprehensive stratigraphical work, this study integrated stable organic carbon isotope analyses, Rock-Eval pyrolysis, iron speciation, and redox-sensitive trace-element geochemistry to reconstruct the lake ecosystem and bottom-water conditions that prevailed when the Jehol Biota inhabited the basin. It further examined the relationship between organic-matter enrichment and fossil preservation. The results were published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology.The Jiufengshan Formation is a classic unit for studying the Jehol Biota, containing the characteristic Eosestheria-Ephemeropsis trisetalis-Lycoptera davidi (“EEL”) assemblage. This study first reports the clam shrimp genus Diestheria in this formation, and assigns the clam shrimp to the Eosestheria-Diestheria assemblage. Together with isotopic age constraints, the paleontological evidence supports the correlation of the Jiufengshan Formation with the Yixian and lower Jiufotang formations in western Liaoning. This indicates that the Dayangshu Basin hosted a lacustrine ecosystem rich in the Jehol Biota, comparable to the basins in the core area.The Jehol Biota in the Jiufengshan Formation is concentrated mainly in the organic-rich shales, which have an average total organic carbon (TOC) content of approximately 7.75% and thus exhibit good hydrocarbon-generating potential. Rock-Eval results show that the organic matter in these shales is dominated by hydrogen-rich Type I kerogen, indicating that lacustrine algae were an important source. This interpretation is consistent with the C/N ratios and relatively negative δ13Corg values. Iron speciation data and redox-sensitive trace elements further reveal distinctive bottom-water chemistry during intervals of organic-matter enrichment: bottom waters were predominantly anoxic and ferruginous during organic-shale deposition, but oxic to suboxic during mudstone deposition.On this basis, the research team proposed a “productivity-preservation coupling” model for the Jehol Biota in the Jiufengshan Formation of the Dayangshu Basin. High algal primary productivity sustained thriving lacustrine communities of fishes, insects, and clam shrimps, while delivering large amounts of organic matter to the lake floor and creating favorable conditions for organic-shale generation. Continued microbial degradation of organic matter consumed dissolved oxygen in the bottom waters and promoted the development of anoxia. With limited sulfide availability, ferruginous bottom waters were characterized by the accumulation of Fe2+. This oxygen-depleted setting inhibited aerobic degradation of organic matter and benthic bioturbation, while reactive iron may have further enhanced preservation through organic-matter stabilization and early mineralization.The above study proposes that high algal productivity supplies organic matter for the ecosystem, whereas ferruginous-anoxic bottom waters promote fossil preservation. Together, these processes generated the organic-rich, fossil-rich lacustrine deposits of the Jiufengshan Formation. This study provides a new geochemical perspective on the expansion, ecological evolution, and exceptional preservation of the Jehol Biota during the Early Cretaceous.This research was supported by the National Natural Science Foundation of China and the Strategic Priority Research Program of the Chinese Academy of Sciences (Category B).Reference: Xue, Y., Jing, Z.H.*, Teng, X., Zhang, X., Liu, P.H., Song, S.Y., Fang, R., Li, G., Zheng, D.R.*, 2026. Biodiversity and paleoenvironmental reconstruction of the Jehol Biota in the Jiufengshan Formation of eastern Inner Mongolia, northeastern China. Palaeogeography, Palaeoclimatology, Palaeoecology, 700, 114111.https://doi.org/10.1016/j.palaeo.2026.114111.Fig.1 Conceptual model for flourishing and preservation of Jehol Biota in Jiufengshan Formation of Shiyoukuangtun section.Fig.2 Fossil clam shrimp from Jiufengshan Formation of Shiyoukuangtun section.Fig.3 Changes in water-column redox conditions recorded in Jiufengshan Formation of Shiyoukuangtun section.
In a study published in the prestigious international journal Proceedings of the National Academy of Sciences (PNAS) on Aug. 11, researchers led by Associate Professor YAO Le from the Nanjing Institute of Geology and Paleontology of the Chinese Academy of Sciences (NIGPAS), together with colleaguesat domestic and international institutions, revealed the process and mechanism of a hyperthermal event during the Earth’s penultimate icehouse, known as the Late Paleozoic Ice Age (LPIA).In a study published in the prestigious international journal Proceedings of the National Academy of Sciences (PNAS) on Aug. 11, researchers led by Associate Professor YAO Le from the Nanjing Institute of Geology and Paleontology of the Chinese Academy of Sciences (NIGPAS), together with colleaguesat domestic and international institutions, revealed the process and mechanism of a hyperthermal event during the Earth’s penultimate icehouse, known as the Late Paleozoic Ice Age (LPIA).This study documents that the Earth experienced a transient global warming event triggered by volcanic activity and orbital pacing during an icehouse climate condition about 300 million years ago. This transient warming event was marked by a ~7.5 ℃ rise in global mean surface temperature (GMST) and an increase in atmospheric CO2 concentrations (pCO2) from ~300 to ~700 ppm.The modern world is experiencing unprecedented warming within an icehouse climate state, resulting in ocean acidification and deoxygenation and widespread deterioration of marine ecosystems. During geological times, multiple hyperthermal events occurred, however, reported hyperthermals during greenhouse climate states are inadequate as an alogues for modern climate warming given their dissimilar boundary conditions (i.e., occurrence during a greenhouse instead of an icehouse climate state).The LPIA is the only deep-time icehouse interval known to have atmospheric pCO2 levels comparable to those of the Quaternary (∼300 ppm). Conodont and brachiopod oxygen isotope (δ18O) recordsfrom North America and the Donets Basin indicate climate warming near the Kasimovian-Gzhelian Boundary (KGB) during the LPIA. However, due to low resolution of the available datasets, the magnitude and temporal expression of these δ18O excursions are inconsistent.The research team conducted secondary ion mass spectrometry (SIMS) oxygen isotopeanalysis (δ18Oapatite) of conodonts from the Naqing and Narao sections in South China and the Usolka section in the southern Urals of Russia. Large negative δ18Oapatite shifts at the KGB record a pronounced warming event, herein named the Kasimovian-Gzhelian Thermal Maximum (KGTM).The KGTM consists of two warming phases, the initial and main warming phases, which were characterized by sea-surface temperature (SST) rises of ~2.0 ℃ and ~3.5 ℃, respectively. Cyclostratigraphy at Naqing constrains the duration of the initial and main phases to~60 kyr and ~35 kyr, respectively. Comparison of SSTs from Usolka with Community Earth System Model (CESM) simulations of pCO2 indicates a rise of atmospheric pCO2 from~300 to ~700 ppm. These results reveal that the KGTM spans the modern climatic state (~300 to 400 ppm), although present-day rates of temperature rise are far higher (~10-15 ℃/kyr) than estimates for the KGTM (~0.04 to ~0.10 ℃/kyr).Mercury isotoperecords (∆199Hg and δ202Hg) indicate the development of photic-zone euxinia (PZE) during the main phase of the KGTM. Marine ecosystems changed at that time, as reflected in decreases in conodont size and diversity and shifts from metazoanto macroalgal reef ecosystems. The coherence of ∆199Hg values (0 to +0.04‰) during the initial phase of the KGTM across South China and the southern Urals indicates a contemporaneous increase in local to regional volcanic activity, which triggered the initial climatic warming. On the other hand, a distinct negative shift in ∆199Hg valuesduring the main phase implies no volcanic activity during that interval.The KGB was marked by coupled and rhythmic variations in the δ18Oapatite and Δ13C (=δ13Ccarb – δ13Corg) records of the Naqing section that conform to 405-kyr long-eccentricity cycles, supporting regulation of atmospheric pCO2 by orbital forcing. During the KGTM event, the initial and main warming phases coincided with maxima of the 100-kyr short-eccentricity cycle and high values of the 405-kyr long-eccentricity cycle.In conclusion, YAO and his colleagues inferred that the KGTM was initiated by volcanic activity with superimposed orbital forcing, which induced carbon emissions and rapid temperature increases. Based on atmospheric CO2 accumulation during the initial phase, sustained orbital forcing is inferred to have triggered positive climate-carbon cycle feedbacks across a critical climatic tipping point, leading to massive carbon release and abrupt large-scale warming during the main phase of the KGTM.A major implication of this study is that humanity needs to pay attention to modest warming events during the modern icehouse climate, which have the potential to lead to accelerated melting of high-latitude icesheets and carbon emissions from permafrost. Through positive climate-carboncycle feedbacks, the Earth system could potentially cross a climatic tipping pointand trigger massive carbon release and abrupt large-scale warming, leading to a major expansion of oceanic anoxia and biodiversity collapse.This study was funded by the National Natural Science Foundation of China, the Youth Innovation Promotion Association of the CAS, and the State Key Laboratory of Paleobiology and Stratigraphy of Nanjing Institute of Geology and Paleontology, CAS.Reference: Le Yao*, Thomas J. Algeo, Qiulai Wang*, Wang Zheng, Qiang Wei*, Yu-ping Qi, Guzel M. Sungatullina, Genming Luo, Ganqing Jiang, Guoqiang Tang, Jian Zhang, Hui Wang, Yaqiu Zhao, Xing Huang, Qiu-Li Li, Xiang-dong Wang, Shucheng Xie, and Xian-Hua Li, 2026. A transient global warming event during Earth’s penultimate icehouse. Proceedings of the National Academy of Sciences of the United States of America. https://doi.org/10.1073/pnas.2601643123.Fig.1 Schematic diagram shows the process and mechanism of the Kasimovian-Gzhelian Thermal Maximum (KGTM) event during the Pennsylvanian Subperiod.Fig. 2 Isotopic and biotic records from the Kasimovian-Gzhelian carbonate successions at the Naqing and Narao sections in South China, and the Usolkasection in southern Urals.The light orange and dark pink bars indicate the initial and main phases of the Kasimovian-Gzhelian Thermal Maximum (KGTM), respectively.Fig.3 Mercury isotope and concentration records from the Kasimovian-Gzhelian carbonate successions at the Naqing, Narao and Usolkasections.The light orange and dark pink bars represent the initial and main phases of the KGTM, respectively.Fig.4 Geochemical, biotic and orbital records for the Kasimovian-Gzheliantransitionat Naqing. The light pink and light blue bars indicate warming and cooling stages of the background interval during the Kasimovian-Gzhelian transition, respectively. The light orange and dark pinkbars represent the initial and main phases of the KGTM, respectively.Fig.5 Comparison of sea-surface temperature (SST) obtained from conodont SIMS oxygen isotopes (δ18Oapatite) and the CESM simulations, andglobal distribution of SST under various atmospheric pCO2 conditions.
The Early Jurassic Toarcian Oceanic Anoxic Event (T-OAE, ~183 Ma) represents a major deep-time hyperthermal in the Phanerozoic, characterized by the rapid injection of isotopically light carbon into the ocean-atmosphere system and a prominent negative carbon-isotope excursion (NCIE), accompanied by global warming and widespread marine anoxia. Traditionally, enhanced silicate weathering and massive marine organic carbon burial during hyperthermals are considered the two primary pathways for drawing down atmospheric CO2 and driving the Earth system toward a cooling recovery. Following this logic, massive carbon burial should have resulted in significant cooling. However, geological records indicate that global high temperatures persisted even after the T-OAE carbon burial phase. As potent greenhouse gases with global warming potentials far exceeding that of CO2, methane (CH4) and nitrous oxide (N2O) emitted from terrestrial lacustrine systems play a pivotal role in perturbing the carbon cycle and exacerbating climate warming. Yet, the emission fluxes of lacustrine N2O and their feedback mechanisms on global climate during deep-time hyperthermals remain poorly constrained.Recently, a collaborative research team led by Dr. HAN Zhong (Nanjing Institute of Geology and Palaeontology, CAS), Dr. GE Yuzhu (Chengdu University of Technology), and Prof. HU Xiumian (Nanjing University), in collaboration with scholars from multiple domestic and international research institutions, conducted high-resolution sedimentary and geochemical analyses on lacustrine records from the Da'anzhai Member in the Sichuan Basin (Fig. 1). By integrating these data with a nitrogen-cycle mass-balance model, the study unveils a climate feedback mechanism wherein a giant terrestrial freshwater lake sustained global high temperatures by emitting massive amounts of N2O during the hyperthermal. These findings were recently published online in the top-tier geoscience journal Geology.The research team focused on the expansive Early Jurassic Sichuan mega-lake, which covered an area of over 230,000 square kilometers (roughly equivalent to 10% of the total surface area of modern global lakes). Analyses of drill-core samples revealed a significant increase in total organic carbon (TOC) within the lacustrine sediments during the T-OAE NCIE interval, accompanied by severe bottom-water anoxia. Crucially, the strata record a pronounced positive excursion in bulk nitrogen isotopes (δ15Nbulk), reaching up to +6.2‰ (Fig. 2). This isotopic signature indicates a substantial intensification of water-column denitrification under anoxic conditions.To decipher why enhanced denitrification led to greenhouse gas emissions, the team delved into the role of trace elements. During denitrification, the reduction of N2O to harmless dinitrogen gas (N2) relies on copper (Cu) as a vital enzymatic catalyst. However, the severe water-column anoxia and organic-rich sedimentation in the Sichuan mega-lake during the T-OAE promoted the extensive complexation of bioavailable dissolved Cu with sulfides and organic matter. Consequently, Cu was firmly sequestered in the sediments, leaving the water column severely depleted in bioavailable Cu for bacterial utilization. This "Cu limitation" effect effectively blocked the final step of the denitrification pathway, forcing the lacustrine system to emit massive amounts of nitrogen into the atmosphere in the form of the greenhouse gas N2O.By constructing an isotopic mass-balance model for the nitrogen cycle, the team conservatively estimated that the Sichuan mega-lake alone released approximately 0.9 to 1.8 Gt (gigatonnes) of N2O into the atmosphere during the T-OAE. Given that the global warming potential of N₂O is 265 to 298 times greater than that of CO2, the greenhouse effect generated by these N2O emissions was sufficient to completely offset the potential cooling effect driven by the massive burial of organic carbon (~460 Gt) within the lake.This study is the first to reveal the positive feedback role of giant terrestrial lakes during deep-time hyperthermals from the unique perspective of "trace-element limitation on lacustrine nitrogen cycling." These findings not only provide a novel mechanistic framework explaining why global warming persisted during and after the T-OAE NCIE, but also offer critical deep-time geological insights into the ecological and environmental risks of increasing greenhouse gas emissions from modern lakes under the current backdrop of global warming, eutrophication, and deoxygenation.This research was jointly supported by the National Key R&D Program of China, the National Natural Science Foundation of China, the Strategic Priority Research Program (B) of the Chinese Academy of Sciences, the National Science and Technology Major Project, and the International Geoscience Programme (IGCP 739).Reference: Ge, Y., Han, Z., Uveges, B.T., Jenkyns, H.C., Kemp, D.B., Cui, Y., Yang, T., Zhang, S., Tian, H., Hu, X., 2026. Intensified lacustrine nitrous oxide emissions linked to global climate warming during the Toarcian Oceanic Anoxic Event. Geology, https://doi.org/10.1130/G54763.1.Fig.1 Early Toarcian paleogeography of the Sichuan Basin and integrated stratigraphy of the LA core.Fig.2 Integrated geochemical, paleontological, and paleotemperature records across the Toarcian hyperthermal. The correlation illustrates the coupling among water-column anoxia, copper (Cu) depletion, and the positive bulk nitrogen-isotope (δ15Nbulk) excursion in the Sichuan megalake, set against the backdrop of global warming and Large Igneous Province (LIP) during the T-OAE NCIE.Fig.3 Mechanistic model and simulation results of hyperthermal-driven lacustrine greenhouse gas (N2O) emissions. (Left) Conceptual model illustrating the physicochemical mechanism wherein water-column anoxia triggers a Cu limitation effect, which inhibits complete denitrification and leads to massive emissions of the potent greenhouse gas N2O. (Right) Nitrogen-cycle mass-balance model quantitatively confirming the marked surge in lacustrine denitrification fluxes during the hyperthermal.
To investigate the total quantity and sources of oxidants required for DOC oxidation during the Shuram event, Dr. ZHANG Yinggang, a postdoctoral fellow at the Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences (NIGPAS), under the supervision of Prof. ZHU Maoyan, conducted quantitative Earth system modeling in close collaboration with Prof. Benjamin Mills and Dr. Fred Bowyer from the University of Leeds. The findings were recently published in Communications Earth & Environment.During the Neoproterozoic–Cambrian transition, seawater carbon isotopic composition experienced multiple dramatic fluctuations. Among them, the negative excursion of carbonate carbon isotopes (with δ13C dropping from ~+5‰ to a minimum of ≤-12‰) during the mid-Ediacaran represents the largest seawater carbon isotope anomaly in Earth’s history. Widely recorded across global continents, it is known as the Shuram (or DOUNCE) event. The Shuram event is widely regarded as a global marine oxygenation event and is thought to be closely linked to the rapid radiation and evolution of early complex life (Fig. 1).However, the driving mechanism behind the extremely negative seawater carbon isotope signal of the Shuram event remains a topic of intense debate. The most widely accepted hypothesis suggests that the event was driven by the oxidation of a massive “dissolved organic carbon (DOC) pool” in the ancient ocean. The oxidation of DOC delivered a vast amount of light carbon isotopes, resulting in the extreme negative shift of seawater dissolved inorganic carbon isotope composition. Yet, this raises a crucial scientific question: oxidizing such a large DOC pool would require consuming immense quantities of oxidants. Given that atmospheric oxygen levels at the time were likely only 1%–10% of modern levels, oxygen alone was far from enough to sustain such large-scale DOC oxidation. Therefore, the source and budget of these oxidants have become one of the core bottlenecks in validating the DOC oxidation hypothesis.To investigate the total quantity and sources of oxidants required for DOC oxidation during the Shuram event, Dr. ZHANG Yinggang, a postdoctoral fellow at the Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences (NIGPAS), under the supervision of Prof. ZHU Maoyan, conducted quantitative Earth system modeling in close collaboration with Prof. Benjamin Mills and Dr. Fred Bowyer from the University of Leeds. The findings were recently published in Communications Earth & Environment.In 2019, a joint Sino-UK research team co-led by Prof. Maoyan ZHU proposed that a massive flux of terrestrial evaporites (sulfate) could have provided sufficient oxidants to fuel DOC oxidation and constrained the potential oxidant flux through forward approach using the COPSE model. However, that model relied on a carbon isotope curve derived solely from Oman, which could not fully represent the global trend. To address this limitation, the team first constructed a global seawater carbon isotope evolution curve based on the global carbonate carbon isotope database coupled with previously published age constraints (Fig.1). Subsequently, using the SCION Earth system evolution model coupled with Monte Carlo inversion techniques, the team quantitatively modeled the DOC oxidation flux and total oxidant demand required to drive this carbon isotope evolution trajectory (Fig.1).The results show that DOC oxidation can successfully explain the severe negative shift in seawater carbon isotopes; however, during the recovery phase of the event, merely “ceasing DOC oxidation” is insufficient to meet the requirement for a rapid rebound in carbon isotopes (Fig. 2). Quantitative modeling demonstrates that a rapid recovery of seawater carbon isotopes can be achieved through the additional effects of enhanced primary productivity and increased organic carbon burial flux (Fig. 2). The Monte Carlo inversion quantitatively calculated that the upper limit of total oxidants required for the Shuram event is approximately 9.3 × 1019 mol. Although this value far exceeds the combined reservoirs of atmospheric oxygen and seawater sulfate at the time, it is well matched by the flux of sulfate that could be supplied by terrestrial evaporites during that period (Fig. 3).This study provides quantitative Earth system evolution modeling evidence confirming that terrestrial sulfate supply was sufficient to meet the oxidant budget required for the Shuram event, offering quantitative constraints for validating the DOC oxidation hypothesis and understanding carbon cycle evolution during this critical transition.This work was jointly funded by the National Key R&D Program of China, the National Natural Science Foundation of China (NSFC), the Jiangsu Excellent Postdoctoral Program, and UK Research and Innovation (UKRI).Reference: Zhang, Y.*, Zhu, M.*, Bowyer, F. T., & Mills, B. J. W. (2026). Revisiting the oxidant budget of the DOUNCE event. Communications Earth & Environment. https://doi.org/10.1038/s43247-026-03855-8.Shields, G. A., Mills, B. J. W., Zhu, M.*, Raub, T. D., Daines, S. J., & Lenton, T. M. (2019). Unique Neoproterozoic carbon isotope excursions sustained by coupled evaporite dissolution and pyrite burial. Nature Geoscience, 12. https://doi.org/10.1038/s41561-019-0434-3.Zhang, Y., Zhu, M.* (2025). Meta-analysis of the DOUNCE event (Shuram/Wonoka excursion): pattern, variation, causal mechanism, and global correlation. Earth-Science Reviews, 261. https://doi.org/10.1016/j.earscirev.2024.105000.Fig.1 Major macroevolutionary events, a reconstructed global seawater δ13C curve, and an inverse modeling strategy within the SCION earth system evolution model.Fig.2 Modeled seawater δ13C variations, their offsets from the reconstructed seawater δ13C curve, and required DOC oxidation rates under baseline and elevated phosphorus-input scenarios.Fig.3 Comparison of required DOC and potential oxidant supply under the DOC-oxidation hypothesis.
Recently, Dr. PAN Bing, an assistant researcher in Professor ZHU Maoyan’s group at the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), in collaboration with a team of researchers from China, the UK, and the USA led by Prof. Guo Junfeng (Chang'an University, China), conducted research on small shelly fossils from South China. Fortunately, among the numerous small shelly fossils from the Shuijingtuo Formation (c. 520 Ma), they discovered the earliest siphuncle-bearing cephalopod, Eoceras shaanxiense, and systematically analyzed 32 specimens of this new species. The scientific results were recently published in Nature.Modern cephalopods are unique among molluscs for their relatively high intelligence. Most extant cephalopods (Coleoidea, represented by squids and octopuses) lack a mineralized external shell; instead, they bear an internal hard or soft shell, or even lack a shell entirely. However, ancestral cephalopods (Nautiloidea) are characterized by heavily mineralized shells with internal structures—such as the siphuncle, chambers, septa, and septal necks—that regulate buoyancy. The siphuncle represents one of the critical innovations in cephalopods evolving from the stem mollusk group. Unfortunately, owing to the lack of a continuous fossil record, the detailed evolutionary pathway of the siphuncle remains unclear. The earliest accepted cephalopod, Plectronoceras cambria, dates from the late Cambrian, which is several tens of millions of years later than the divergence time of cephalopods estimated by molecular clocks during Cambrian Explosion (early Cambrian). However, the abundant, multi-phylum microfossils known as 'small shelly fossils' that occur worldwide in the early Cambrian may offer great potential for discovering the earliest cephalopods.Recently, Dr. PAN Bing, an assistant researcher in Professor ZHU Maoyan’s group at the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), in collaboration with a team of researchers from China, the UK, and the USA led by Prof. Guo Junfeng (Chang'an University, China), conducted research on small shelly fossils from South China. Fortunately, among the numerous small shelly fossils from the Shuijingtuo Formation (c. 520 Ma), they discovered the earliest siphuncle-bearing cephalopod, Eoceras shaanxiense, and systematically analyzed 32 specimens of this new species. The scientific results were recently published in Nature.Based on observations of specimens preserved through different types of phosphatization, using scanning electron microscopy (SEM) and micro-computed tomography (micro-CT) (Fig. 1), the researchers revealed the overall external morphology and internal anatomy of Eoceras. Eoceras is millimeter-sized, with an orthoconic shell, an oblique apertural margin, multiple septa, and a ventrally situated segmented tube that appears to bridge the septa via minute canals (Fig. 2). Through comprehensive comparison with the internal structures of typical siphuncle-bearing cephalopods, the segmented tube of Eoceras is interpreted as a siphuncle. Therefore, they argue that Eoceras is likely a very early cephalopod—more specifically, an intermediate evolutionary stage between earlier chambered shells and later species with more developed buoyancy systems.They also outline a general early evolutionary pathway for cephalopods: firstly, early cephalopods originated from a taxon with orthoconic shells and multiple septa; secondly, they evolved a sealed, segmented siphuncle within the orthoconic shell; and thirdly, they formed a true siphuncle with septal necks and connecting rings. Considering its primitive and simple system for regulating buoyancy, Eoceras may have had a mostly benthic mode of life. However, the fossil lacks several features seen in later cephalopods, and its soft-body anatomy remains uncertain. Future discoveries and further studies of similar Cambrian fossils may help clarify the earliest evolutionary history of cephalopods and the origins of their distinctive shell architecture.This research was supported by the National Natural Science Foundation of China (NSFC), the National Key Research and Development Program of China, and the Opening Foundation of the State Key Laboratory of Continental Evolution and Early Life.References: Song, Z.C., Pan B., Guo, J.F.*, Vinther, J.*, Li, G.X., Han, J., Van Iten, H., Zhao, X.F., Pei, X.Z., Peng, J.X., Qiang, Y.Q., Zhang, B.Y., Wen, H.J.*, 2026. Earliest siphuncle-bearing cephalopod from the early Cambrian. Nature. https://doi.org/10.1038/s41586-026-10868-y.Fig. 1 Preservation types of Eoceras gen. nov. from the Cambrian Shuijingtuo Formation, South ChinaFig. 2 Overall out morphology and inner anatomy of the shell of EocerasFig. 3 Hypothesized phylogenetic position and life reconstruction of Eoceras gen. nov.
Associate Professor HAN Zhong from the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), in collaboration with researchers from domestic and international research institutions,extracted and analyzed the silicate fractions (acid-insoluble residues) hosted in Early Jurassic low-latitude shallow-marine carbonate platforms. By integrating their magnesium isotope (δ26Mg) variations with an Earth System Model, the team revealed the amplifying effect of extreme hydroclimate on continental weathering during the hyperthermal event. These findings were published online on July 24 in the premier international geoscience journal, Geology.Continental silicate weathering serves as a critical negative feedback mechanism regulating the global carbon cycle and climate over geological timescales. The Toarcian Oceanic Anoxic Event (T-OAE, ~183 Ma) in the Early Jurassic was a prominent global warming episode accompanied by widespread marine anoxia and an intensified hydrological cycle, representing a classic deep-time hyperthermal. As a hub for global climate regulation, low-latitude silicate weathering is highly sensitive to climatic shifts. However, limited by the spatial heterogeneity of geological records and the scarcity of quantitative proxies, the response processes and dynamic mechanisms of low-latitude chemical weathering to Toarcian warming have remained poorly understood.To address this issue, Associate Professor HAN Zhong from the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), in collaboration with researchers from domestic and international research institutions,extracted and analyzed the silicate fractions (acid-insoluble residues) hosted in Early Jurassic low-latitude shallow-marine carbonate platforms. By integrating their magnesium isotope (δ26Mg) variations with an Earth System Model, the team revealed the amplifying effect of extreme hydroclimate on continental weathering during the hyperthermal event. These findings were published online on July 24 in the premier international geoscience journal, Geology.The research team conducted Mg-isotope analyses on two low-latitude profiles from the Early Jurassic Toarcian, located in the then-Southern Hemisphere (Kioto Carbonate Platform, Tibet) and Northern Hemisphere (Apennine Carbonate Platform, Italy) (Fig. 1). The results show that following the Pliensbachian-Toarcian (Pl-To) boundary (~184 Ma, corresponding to the Karoo Large Igneous Province activity), both sections recorded a significant positive excursion in Mg isotopes. This trend coincides with the initial rise in paleoseawater temperatures, indicating a gradual intensification of continental chemical weathering. Interestingly, this enhanced weathering signal continued to rise, reaching its maximum during the onset interval of the T-OAE negative carbon-isotope excursion (NCIE) (corresponding to the Ferrar Large Igneous Province activity) (Fig. 2), demonstrating a distinct delayed temporal response. The study suggests that early carbon emissions at the Pl-To boundary did not immediately trigger significant changes in the global weathering system. Instead, cumulative atmospheric carbon needed to surpass a critical tipping point to trigger the severe climatic and environmental crises during the T-OAE NCIE, thereby pushing silicate weathering to its peak.To explore the physical mechanisms behind this weathering enhancement, the team conducted paleoclimate simulations using the Community Earth System Model (CESM). The simulations indicate that in tectonically quiescent low-latitude regions, thick soil mantles acted as a shielding layer, preventing contact between the underlying bedrock and fluids. Simple temperature increases alone (i.e., the Arrhenius effect) were insufficient to drive the observed weathering surge (Fig. 3). However, the hyperthermal event triggered extreme hydroclimatic volatility (e.g., tropical cyclones, intense precipitation, and flash floods). Such extreme precipitation and surface runoff stripped the surface soil cover, directly exposing the underlying unweathered bedrock and thereby drastically amplifying the intensity of chemical weathering.By utilizing the Mg isotopes of carbonate-hosted acid-insoluble residues, this study confirms the weathering response of low-latitude regions during an extreme greenhouse period. From the perspective of "soil stripping–weathering coupling," it elucidates the role of extreme hydroclimatic events in accelerating Earth's climate self-regulation (weathering carbon sink). This research provides crucial theoretical support for understanding the non-linear coupling between the climate system and biogeochemical cycles during deep-time hyperthermals.This research was jointly funded by the National Key R&D Program of China, the National Natural Science Foundation of China (NSFC), the Research Fund for International Scientists (NSFC), the Italian Ministry of University and Research, and the International Geoscience Programme (IGCP 739).Reference: Han, Z.*, Hu, Z., Guo, J., Parente, M., Kemp, D.B., Remírez, M.N., Yuan, S., Li, X., Hu, Y., Jenkyns, H.C., Chen, X., Franceschi, M., Hu, X.*, 2026. Magnesium isotopes reveal hydroclimatically amplified low-latitude weathering during the early Toarcian. Geology, https://doi.org/10.1130/G54555.1.Fig. 1. Early Toarcian paleogeographic map. The map shows the locations of the two low-latitude study sections (Nianduo, Tibet, and Mercato San Severino, Italy), along with the distributions of the Karoo and Ferrar Large Igneous Provinces (LIPs) and storm deposit records (yellow dots).Fig. 2. Integrated Early Jurassic stratigraphic and geochemical correlation chart. It displays the positive excursion trend of magnesium isotopes (δ26Mg) in the studied sections and its relationship with carbon isotopes (δ13C), storm deposit records, paleotemperature changes, and the activity of Large Igneous Provinces (Karoo and Ferrar).Fig. 3. Climate simulation results and conceptual model of continental weathering evolution. The upper panels (A-D) show the spatial distribution changes in global annual mean surface temperature and precipitation simulated by the CESM under different atmospheric CO2 concentrations. The lower panels (E-F) illustrate the physical mechanism by which climate change drives enhanced continental weathering, wherein extreme hydroclimatic events (e.g., tropical cyclones and intense precipitation-induced runoff) strip the surface soil layer, exposing the underlying unweathered bedrock, thereby intensifying chemical weathering and leading to the observed Mg-isotope excursion coupling.
Recently, LI Yanda, a PhD student at the University of Bristol, together with Professor CAI Chenyang from the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), and co-authors described a distinctive new genus of lampyroid beetles from mid-Cretaceous Kachin amber of Myanmar. Phylogenetic analyses indicate that the new genus, Icaroramus, likely belongs to the extinct family Cretophengodidae. The fossil specimen preserves elaborate antennae alongside fully intact abdominal light-emitting organs. The co-occurrence of these two diagnostic traits in a single fossil individual provides pivotal evidence for reconstructing the early evolution of sensory and signalling systems in fireflies and their close relatives. This research was published in Proceedings of the Royal Society B.The capacity of insects to perceive environmental cues and transmit information constitutes a critical foundation for their remarkable evolutionary success and extraordinary taxonomic diversity on Earth. Over their long evolutionary history, insects have evolved sophisticated sensory organs and diverse signal communication strategies, relying on chemical odours, acoustic signals, colour patterns and bioluminescence for interindividual signalling. Nevertheless, direct fossil evidence documenting the origin and evolutionary trajectories of these intricate sensory and communication systems, as well as the interplay between distinct signalling modalities, remains scarce, given the extremely low preservation potential of soft tissues and delicate microstructures.Recently, LI Yanda, a PhD student at the University of Bristol, together with Professor CAI Chenyang from the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), and co-authors described a distinctive new genus of lampyroid beetles from mid-Cretaceous Kachin amber of Myanmar. Phylogenetic analyses indicate that the new genus, Icaroramus, likely belongs to the extinct family Cretophengodidae. The fossil specimen preserves elaborate antennae alongside fully intact abdominal light-emitting organs. The co-occurrence of these two diagnostic traits in a single fossil individual provides pivotal evidence for reconstructing the early evolution of sensory and signalling systems in fireflies and their close relatives. This research was published in Proceedings of the Royal Society B.The most striking morphological trait of Icaroramus lies in its unique antennae. The antennae consist of twelve segments; antennomeres 4 to 11 each bear two pairs of lateral rami with disparate morphologies. The proximal pair of rami at the base of each antennomere is elongated with dilated apices and coarse setae, whereas the medial pair near the segment midpoint is shorter, slender and covered only with fine hairs. Such heteroramose antennae—characterised by two morphologically distinct pairs of lateral branches on a single antennomere—are unprecedented across the entire Coleoptera order. From a developmental evolutionary perspective, this specialised antennal morphology may arise from partial reactivation of the antennal segmentation programme within individual antennomeres, generating extra branching outgrowths.Numerous extant insect lineages that locate mates via chemical communication possess well-developed branched antennae to enhance detection of trace airborne pheromones. The highly complex ramified antennae of Icaroramus imply that this extinct lampyroid probably relied heavily on pheromonal cues during mate searching. Furthermore, the clear morphological differentiation between the two sets of antennal rami may reflect functional partitioning of olfactory sensilla, enabling the beetle to discriminate between distinct chemical signals. Such highly specialised chemosensory capacity demonstrates that Cretaceous lampyroids had evolved sophisticated ecological adaptations.By contrast, the exact biological function of the abdominal photic organs cannot be definitively resolved solely from fossil material. Extant firefly clades that use light signals for courtship generally exhibit simplified antennae, yet Icaroramus combines elaborate light organs with highly branched antennae—a trait combination inconsistent with most modern fireflies dependent on luminous mating signals. Accordingly, the bioluminescent organs of Icaroramus most likely functioned for aposematic anti-predator defence, though a supplementary role in mate attraction cannot be entirely ruled out.Collectively, Icaroramus reveals that lampyroid beetles already possessed both highly specialised sensory structures and functional bioluminescence by the Cretaceous (~100 Ma), offering novel fossil insights into the evolutionary origins of the complex signalling machinery of fireflies.This work was supported by the National Key Research and Development Program of China. Reconstruction illustrations were created by illustrator Dinghua Yang.Reference: Li, Y.-D., Kundrata, R., Huang, D., Tin Aung Myint & Cai, C. (2026) A firefly relative that smelled and glowed: evidence for complex signalling systems in Cretaceous lampyroids. Proceedings of the Royal Society B, 293, 20260295. https://doi.org/10.1098/rspb.2026.0295.Fig.1 Icaroramus perisi and its unique heteroramose antennaeFig.2 Phylogenetic tree showing the systematic placement of the genus IcaroramusFig.3 Ecological reconstruction illustrating luminous Icaroramus in a Cretaceous forest
Recently, SHI Kaiyan, a master’s student at the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), under the supervision of Prof. HUANG Bin and in collaboration with Prof. RONG Jiayu and Prof. ZHAN Renbin, reported for the first time an EC Fauna from the Wulipo Bed in Meitan, Guizhou Province. The result was published in Palaeoworld.The Edgewood–Cathay (EC) brachiopod fauna, typified by Cathaysiorthis, is an important fossil assemblage for recognizing the survival to early recovery interval following the Late Ordovician mass extinction (LOME). It records the persistence of surviving “Ordovician-type” groups, the emergence of new taxa, and the reorganization of benthic communities after the disappearance of the Hirnantia Fauna. It is therefore of considerable significance for understanding brachiopod macroevolution and palaeobiogeographical patterns across the Ordovician–Silurian transition.Recently, SHI Kaiyan, a master’s student at the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), under the supervision of Prof. HUANG Bin and in collaboration with Prof. RONG Jiayu and Prof. ZHAN Renbin, reported for the first time an EC Fauna from the Wulipo Bed in Meitan, Guizhou Province. The result was published in Palaeoworld.A total of 1,224 brachiopod specimens were obtained, representing 13 species in 13 genera. The fauna is dominated by Eospirigerina, Hindella, and Cathaysiorthis (Fig. 1). Non-metric Multidimensional Scaling (NMDS) and network analyses show that the northern Guizhou EC Fauna is closely related to the typical EC faunas of eastern China but is clearly distinct from the Hirnantia Fauna (Fig. 2). This discovery extends the known distribution of the early EC Fauna to the southwestern margin of the Yangtze Platform.Within this fauna, “Ordovician-type” clades, particularly Orthida and Strophomenida, remain dominant, while newly emerged taxa such as Cathaysiorthis are also present, indicating that the fauna belongs to the survival to early recovery interval following the mass extinction. Compared with the possibly younger Cathaysiorthis fauna from Xichuan, He’nan Province, in which the proportion of “Silurian-type” clades had increased, the northern Guizhou fauna represents an earlier stage of brachiopod-community recovery. It also provides new material for comparing regional differences among contemporaneous faunas from eastern China, northern Guizhou, and northeastern Yunnan.The study also reassessed the relationships among the Wulipo Bed, Shiqian Formation, and Weiba Formation. “Wulipo Bed” is the earliest valid name applied to this lithostratigraphic unit. However, the name “Wulipo” had already been used for a Permian formation, resulting in a nomenclatural conflict. The Stratigraphic Lexicon of China: Permian System considers the Permian Wulipo Formation to represent the upper part of the Yangshan Formation and suggests that it should not be recognized as an independent formation. Moreover, the Compendium of Chinese Lithostratigraphic Nomenclature (National Stratigraphic Committee, 2017) lists both names. The present study therefore temporarily retains “Wulipo Bed” as a valid bed-rank unit.Because the Shiqian and Weiba formations are each less than 4 m thick and are too thin to serve as mappable lithostratigraphic units, they are downgraded to the Shiqian Bed and Weiba Bed, respectively, and are regarded as junior subjective synonyms of the Wulipo Bed (Fig. 3). This revision helps to standardize the lithostratigraphic framework across the Ordovician–Silurian boundary in northern Guizhou and adjacent regions, providing a more stable basis for regional stratigraphic correlation and studies of biotic macroevolution.The brachiopod fauna of the Wulipo Bed shows an upward succession from the Eospirigerina–Hindella Association to the Eospirigerina–Cathaysiorthis Association. The palaeoecological setting changes from Benthic Assemblage 2 (BA2) to Benthic Assemblage 3 (BA3), indicating progressive deepening of the water. This succession records a transgressive event after the second phase of the LOME and provides palaeoecological evidence for post-glacial warming, ice-sheet melting, and sea-level rise.The study expands the known palaeogeographical range of the early Cathaysiorthis fauna and reveals the composition and ecological changes of the earliest recovery communities in the southwestern part of the South China plate. It also provides key new data for standardizing the regional stratigraphic framework and understanding the reorganization of benthic ecosystems after the mass extinction.Reference: Kai-Yan Shi, Bing Huang*, Ren-Bin Zhan, Jia-Yu Rong. 2026. A new Edgewood-Cathay Fauna from the Wulipo Bed (uppermost Ordovician to lowermost Silurian) in South China and its palaeoecological significance. Palaeoworld 35, 201152. https://doi.org/10.1016/j.palwor.2026.201152.Fig. 1. Representative taxa of the EC Fauna from northern Guizhou.Fig. 2. Network analysis showing that the studied fauna is closely related to the EC faunas of eastern China but clearly distinct from the Hirnantia Fauna.Fig. 3. The Shiqian Formation in the Shiqian area and the Weiba Formation in the Zhenxiong area, each less than 4 m thick, are revised as the Shiqian Bed and Weiba Bed and regarded as junior subjective synonyms of the Wulipo Bed.
The late Paleozoic witnessed intense tectonic activity, which played a major role in driving the evolution of Earth’s surface systems. Two major continent-continent collisional belts formed during the late Paleozoic, namely the Hercynian orogen and the Uralian orogen. In addition, a series of subduction-related orogenic belts formed around these continents during the late Paleozoic, including the Cordilleran orogenic belt, the Terra Australis orogenic belt, and the Central Asian orogenic belt. Meanwhile, the South China Craton was located to the northeast of the Paleo-Tethys Ocean, at the confluence of the Panthalassa Ocean to the east and the Paleo-Tethys Ocean to the west. However, the tectonic setting of South China during the late Paleozoic remains ambiguous due to the lack of sufficient magmatic and metamorphic records, in addition to the restricted siliciclastic sedimentary system, which hampers our understanding of the regional tectonic evolution and geodynamic processes.As the first-order control on changes in paleogeography, different tectonic settings of continental margins would exert different influences. Therefore, reconstructing the paleogeographic evolution processes of South China can provide additional constraints on the tectonic setting of the South China Craton. Over the past decade, numerous late Paleozoic detrital zircons have been reported from Devonian to Triassic siliciclastic strata in South China, providing an opportunity to explore its tectonic setting and geodynamics. The occurrence of two late Paleozoic magmatic rocks, with ages of 334 Ma and 317 Ma, from the southeastern region of South China, confirms magmatic activity in southeastern South China. Most of these studies focused on the tectonic setting of southeastern South China, and different models have been proposed to account for those magmatic activities. By contrast, the northwestern margin of South China was claimed to be a passive continental margin, although its tectonic setting has received limited attention. Therefore, reconstructing the paleogeographic evolution of South China is critical for elucidating its late Paleozoic tectonic setting, which remains poorly understood.Here, Prof. CHEN Jitao and QIE Wenkun from the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), leading a team including assistant researchers GAO Biao and ZHONG Yutian, and Master’ degree candidate GUAN Yifan, conducted heavy mineral assemblage analyses, detrital zircon cathodoluminescence (CL) imaging, geochronological analyses, and zircon geochemical analyses, to explore the provenance and paleogeographic evolution of South China during the late Paleozoic. The results of this study were recently published in the Journal of Asian Earth Sciences.The three samples from the MLB section show relatively similar zircon U–Pb age spectra. Specifically, they consist of two major age clusters at 470–410 Ma and 860–800 Ma, with peaks at ca. 440 Ma and 830 Ma. Six subordinate age populations peak at 2.5 Ga, 1.8 Ga, 990 Ma, 910 Ma, 790 Ma, and 680 Ma. The remaining sporadic zircons fall within the age ranges of 3.1–2.6 Ga, 2.4–1.9 Ga, and 1.7–1.0 Ga. In conclusion, the siliciclastic sandstones in the MLB section have broadly similar provenance compositions, including the early Paleozoic Kwangsian orogenic rocks from the Cathaysia Block, detritus from the eastern Yangtze Block, and material from the central Jiangnan orogenic belt.Although the above provenance analysis indicates a relatively stable source-to-sink system for the MLB section, a provenance shift can still be recognized. The proportion of zircons aged 470–410 Ma, derived from the Kwangsian orogenic belt in the Cathaysia region, decreases from 24% in sample MLB-0 to 16% in MLB-71.8, and finally to 8% in MLB-129. In contrast, the proportion of zircons peaking at ca. 830 Ma (860–800 Ma), derived from the central Jiangnan fold belt in the eastern Yangtze Block, increases from 15% in sample MLB-0 to 32% in MLB-71.8, and then decreased slightly to 26% in MLB-129.A Monte Carlo test was used to assess the error ranges of the detrital contributions from the Cathaysia Block for the three MLB sandstone samples. Considering their error ranges, the probability of a strict decreasing trend in the percentage of the 470–410 Ma zircon cluster is about 64.34%, and the probability of MLB-0 > MLB-129 is about 99.91%. To reveal the long-term paleogeographic evolution of South China, a compilation of detrital zircon ages from late Paleozoic sedimentary rocks was conducted. Correspondingly, a decreasing contribution of detrital zircons aged 470–410 Ma can also be observed in the compiled detrital zircon age spectra of late Paleozoic strata in the Cathaysia Block, further supporting the gradual topographic flattening of the Cathaysia landmass during the late Paleozoic. By contrast, the age spectra of the Yangtze region remain similar over ~120 Myr (from the Early Devonian to the Early Permian), indicating a stable provenance system, which is consistent with a passive continental margin setting. In addition, the tectonic settings of the Yangtze and Cathaysia regions can also be distinguished on the CA–DA diagram.This study was supported by the National Natural Science Foundation of China.Reference: Biao Gao*, Yutian Zhong, Yifan Guan, Wenkun Qie, Jitao Chen*. Provenance analysis of latest Devonian to early Carboniferous siliciclastic deposits in central South China: Implications for paleogeographic change and tectonic setting of the South China Craton. Journal of Asian Earth Sciences, 310:107202. https://doi.org/ 10.1016/j.jseaes.2026.107202.(a) Global paleogeographic reconstruction and tectonic framework at ca. 350 Ma. (b) Lithofacies paleogeography of South China in the earliest Carboniferous, showing the location of the MLB section. (c) Stratigraphic and lithological column of the MLB section, showing sample locations (stars).Violin plots of detrital zircon age groups from the Kwangsian orogenic belt (480–410 Ma). Orange circles represent the proportions of the zircon age cluster at 860–810 Ma.Relative probability plots for detrital zircon ages from late Paleozoic strata in the Cathaysia region (a) and Yangtze region (b). (c) Tectonic setting discrimination diagram. The lines in (c) represent these age compilations from the Yangtze and Cathaysia regions, shown in different colors.Conceptual illustration of the paleogeographic reconstruction and tectonic setting of the South China Craton during the latest Devonian to early Carboniferous. (a) Paleogeographic evolution of the provenance system of the MLB succession. (b) Tectonic and geodynamic model of South China during this interval.
