The study, published in the Journal of Micropalaeontology, is, according to its authors, the first attempt to apply deep learning to the automated identification of Devonian miospores. The team, led by Vitalina Lokteva and corresponding author Vahram Serobyan of the Institute of Geological Sciences of the National Academy of Sciences of Armenia, together with Martin Tetard, Pierre Breuer, and Taniel Danelian, focused on three species of enormous biostratigraphic value: Teichertospora torquata, Geminospora lemurata, and Samarisporites triangulatus. These spores are widely used to define global biozones across the ancient continents of Gondwana and Laurussia, and they play a particularly important role in hydrocarbon exploration, notably in Saudi Arabia, where Devonian spore-based stratigraphy helps geologists date and correlate the rock layers that host oil and gas reservoirs.

The material came from the Ertych section in central Armenia, one of the region’s best-known localities for palynological research. Fourteen beds of upper Frasnian age were sampled during several field campaigns, and productive miospore assemblages were recovered from twelve of them. Standard palynological preparation yielded three to five slides per sample, which were examined with a Leica DM2700 transmitted-light microscope. Every specimen that a specialist qualitatively identified as one of the three target species was photographed individually with a Flexacam C5 camera, producing a library of 209 microphotographs that formed the raw material for the machine learning pipeline.

Each of those 209 images was then annotated by hand using the web-based platform Roboflow. An operator drew a rectangular bounding box around every individual spore and recorded the image identifier, class label, and microscope magnification as metadata. The resulting detection dataset contained five classes: the three target species, which together accounted for roughly 57 percent of the annotations, an “other” class comprising non-target miospore taxa, and a background class dominated by images without miospores, filled largely with fragments of plant debris known as phytoclasts. The images were divided into training, validation, and test subsets in a 70/20/10 split, with the test set kept strictly separate so that no image used in evaluation had ever been seen during training.

The architecture of the workflow reflects a growing consensus in automated microscopy: detection first, classification second. In the detection stage, the team deployed YOLOv11, a one-stage object detection network that predicts bounding-box coordinates, objectness scores, and class probabilities in a single forward pass. Initialized with weights pretrained on the COCO image dataset and trained with a single class label of “miospore”, the detector was applied to the test micrographs using a confidence threshold of 0.7. Its performance was striking. Precision, the fraction of predicted boxes that were correct, reached 0.98; recall, the fraction of true objects the model actually found, was a perfect 1.0; and the mean average precision at an intersection-over-union threshold of 0.5 came in at 0.995, averaging 0.906 across the stricter range of thresholds from 0.5 to 0.95.

Crucially, the detection stage did more than simply find the spores. For each detection, the pipeline stored the bounding-box coordinates, a cropped image patch stripped of its cluttered background, and the area of the crop, measured in pixels and calibrated to square micrometers. This inference step produced 159 background-free spore crops, which became the classification dataset, split 70/15/15 into training, validation, and test subsets. The bounding-box area was retained as an auxiliary numeric feature, a simple piece of morphometric information that would later prove surprisingly valuable when taxa differed mainly in size.

For the classification stage, the researchers compared three convolutional neural networks, all implemented in PyTorch and trained through transfer learning, in which the pretrained convolutional feature extractors were frozen and only the task-specific heads were fine-tuned on the miospore data. VGG16, a 16-layer network that stacks small 3×3 convolutions, served as a stable, well-understood baseline. ResNet-18, an 18-layer network with residual skip connections that prevent optimization problems in deeper models, offered a lightweight and efficient feature extractor. EfficientNet-B0, the smallest member of the EfficientNet family, provided a compact architecture suited to limited data and compute. During training, images were resized to 224 by 224 pixels and augmented on the fly with flips, rotations of up to 15 degrees, color jitter, normalization, and random erasing, while validation images underwent only resizing and normalization to keep the evaluation unbiased.

The results, averaged over ten independent training runs, showed a clear hierarchy. ResNet-18 achieved the highest mean test accuracy at 87.9 percent, along with a Matthews correlation coefficient of 0.85, a metric that condenses the entire multiclass confusion matrix into a single value between minus one and one and is robust to the class imbalance typical of palynological datasets. VGG16 posted the highest macro-F1 score of 87.3 percent with a comparable test accuracy of 87.5 percent, while EfficientNet-B0 trailed on every metric, with 79.6 percent accuracy, 76.4 percent macro-F1, and an MCC of 0.75. In the best single runs, both ResNet-18 and VGG16 reached a test accuracy of 95.8 percent. The confusion matrices revealed that all three classifiers identified T. torquata flawlessly, with an F1 score of 1.00, likely because that species is large, reaching 85 to 140 micrometers, and bears a distinctive cavate structure, sub-triangular outline, and clear trilete mark. G. lemurata, a cavate spore of roughly 40 to 50 micrometers with a rounded outline, scored between 0.88 and 0.92. S. triangulatus proved hardest, with F1 scores of 0.73 to 0.80, probably because poorer preservation in the Armenian material obscures its diagnostic cone-shaped sculpture and indistinct trilete mark.

The authors are candid about the limits of the proof of concept. The classification dataset of 159 crops is small by deep learning standards, and the heterogeneous “other” class, which lumps together many different taxa, inevitably adds within-class variability. All images were acquired with a single microscope and a single preparation protocol, so performance may shift when the method meets material prepared and imaged under different conditions. Even so, the pipeline’s average per-class accuracies of 84.5 to 86.25 percent fall comfortably within the range of 83.3 to 99.8 percent reported in recent palynological and microfossil classification studies, a notable achievement for fossil material, which is consistently harder to classify than the pristine modern pollen on which most earlier models were trained. Prior work has shown that accuracy drops when models trained on modern pollen are applied to damaged or fossil specimens, making the team’s direct focus on fossil Devonian spores a meaningful step forward.

The researchers are careful to position the tool as an assistant rather than a replacement for expert knowledge. Supervised AI classification remains dependent on expert-defined taxonomic concepts and carefully curated training data, and the workflow is best understood as a screening and decision-support system that standardizes routine identifications, reduces observer bias, and improves reproducibility. The path forward is clear: enlarging the image dataset, broadening taxonomic coverage, incorporating material from additional sections and laboratories, and coupling the detector with automated slide-scanning systems to raise throughput. The code and annotated dataset have been released on Zenodo, inviting the community to build on the work. If the approach scales as hoped, the same two-step logic could extend to other fossil groups, including Paleozoic marine phytoplankton such as acritarchs and prasinophytes, and even scolecodonts, bringing the routine dating of sedimentary rocks, from academic biostratigraphy to oil exploration, into the age of machine perception.

Subject of Research: Automated detection and identification of Devonian miospores using convolutional neural networks

Article Title: Artificial intelligence applied to the automated detection and identification of Devonian miospores

Article References: Lokteva, V., Serobyan, V., Tetard, M., Breuer, P., & Danelian, T. (2026). Artificial intelligence applied to the automated detection and identification of Devonian miospores. Journal of Micropalaeontology, 45(1), 405-413. https://doi.org/10.5194/jm-45-405-2026

Image Credits: AI Generated

DOI: 10.5194/jm-45-405-2026

Keywords: artificial intelligence, convolutional neural networks, Devonian miospores, palynology, biostratigraphy, YOLOv11, ResNet-18, microfossils, upper Frasnian, Armenia, fossil spores, automated microscopy

The research, led by Lei Zhang of Chengdu University of Technology together with an international team spanning China, France, and Sweden, focused on a class of fossils that most people would walk right past: microscopic scraps of the outer body coverings, or cuticles, of soft-bodied animals. These fragments were extracted from roughly 2,000 kilograms of phosphatic dolostone collected at the Muyangxi section in the Three Gorges area of Hubei Province. The team dissolved the rock in weak acetic acid over two months, sieved the residue, and then examined the surviving fossils under a field emission scanning electron microscope after coating them in gold-palladium alloy.

What emerged from the acid bath was extraordinary. The fossils belong to a preservation style known as Orsten-type, in which early diagenetic phosphatization replicates delicate cuticular surfaces in three dimensions with fidelity down to subcellular scales. Many specimens exceed two millimeters in length even in fragmentary form, and some hint at original animals approaching centimeter scale, a striking size for creatures this early in Earth history. Based on distinctive patterns of ornamentation, spines, and sclerites, the team recognized six forms representing at least four distinct ecdysozoan taxa, the group of molting animals that includes scalidophoran worms and panarthropods.

Ecdysozoa are, by any measure, one of evolution’s greatest success stories. The clade encompasses arthropods, the most species-rich animal phylum on Earth, along with nematodes, priapulid worms, kinorhynchs, and their relatives. Molecular clock analyses consistently place the origin of the group in the late Ediacaran Period, but their earliest fossil record has been frustratingly sparse and controversial. The best evidence comes from the slightly older Kuanchuanpu Formation, also in South China, which has yielded a remarkable menagerie of phosphatized worms and sac-like creatures, including the famous Saccorhytus coronarius, once touted as the earliest known deuterostome and now firmly repositioned within the ecdysozoan stem group.

The new Yanjiahe material adds crucial texture to this picture. Among the six forms, several stand out. Form C, the most abundant in the collection, bears at least four distinct spine types, including hollow tubular spines with dome-shaped bases and coniform spines with depressed funnel-shaped bases, alongside smaller hook-like spines with what the authors describe as cowboy-hat-shaped basal expansions. The interspinal cuticle displays a hierarchical reticulated pattern of small polygons superimposed by larger orbit-like meshes. These features invite comparison with the spiny introverts of priapulid worms and the armored bodies of early kinorhynchs such as Eokinorhynchus rarus.

The most provocative specimens, however, are Forms A and B, which carry lateral branches that may represent appendages. Form A is a vermiform cuticle lacking spines entirely, instead showing broad sinuous ridges running obliquely across the body and finer striations just a few micrometers wide. Its most distinctive feature is a series of paired, tubular projections extending laterally from the main cylindrical body. These structures resemble the lobopodous limbs of early panarthropods, the soft-legged ancestors from which arthropods, velvet worms, and tardigrades all descended. If the interpretation holds, Form A would rank among the earliest direct body fossil evidence of appendages in the entire ecdysozoan lineage.

The timing is significant. Trace fossils such as Rusophycus avalonensis and the scratch marks of Monomorphichnus, found in Fortunian-age rocks of southern China, Kazakhstan, and Newfoundland, have long hinted that appendage-bearing animals were moving across and through sediments at this time. But a frustrating gap persisted between these tracks and the first unambiguous body fossils of euarthropods, which do not appear until Cambrian Stage 3, millions of years later. Form A, with its annulated trunk and paired lateral appendages, could help bridge that gap, suggesting a Fortunian expansion of motile, appendage-bearing bilaterians whose soft anatomy was simply too fragile to fossilize in most settings.

The researchers are careful to note the limits of the evidence. The appendages of Form A lack the transverse annulations and terminal claws typical of walking lobopods, and their lateral rather than ventrolateral insertion suggests they may have served for paddling or sediment manipulation rather than weight-bearing locomotion. The team also considered and rejected alternative identities for the branches, including annelid parapodia and palaeoscolecid setae. Form B, with its clearly segmented trunk of three annuli and densely spinose surface, might instead represent a stem-group kinorhynch, its branches interpreted as specialized spines rather than true limbs. Definitive taxonomic placement, the authors concede, will require additional fossils.

Beyond the individual forms, the assemblage tells a broader ecological story. The three fundamental ecdysozoan body architectures, sac-like forms, vermiform worms, and appendage-bearing panarthropods, all appear to have been established during the initial phase of the Cambrian explosion. The widespread development of spines and sclerites across these lineages points to their adaptive importance, likely serving for protection, anchoring in sediment, and other ecological functions. Meanwhile, the complex burrow systems of Treptichnus pedum at the Ediacaran-Cambrian boundary record the so-called Substrate Revolution, when vermiform animals began churning seafloor sediments in earnest, reshaping entire ecosystems from the bottom up.

The Yanjiahe Formation itself, dated radiometrically to between roughly 540 and 526 million years ago, sits squarely within this transformative interval, coinciding with a major carbon isotope excursion and faunal turnover. Its lower beds, previously underexplored compared with the celebrated Kuanchuanpu deposits, are now proving to be a treasure trove in their own right. As systematic excavation of Orsten-type fossils continues, each acid-dissolved kilogram of ancient rock promises to reveal more about how Earth’s most successful animal groups, from mosquitoes to lobsters, took their very first evolutionary steps in the shallow seas of the earliest Cambrian.

Subject of Research: Early Cambrian ecdysozoan microfossils from the Yanjiahe Formation of South China

Article Title: Cuticular microfragments from the lower Cambrian Yanjiahe Formation, China: insights into ecdysozoan biodiversity at the dawn of animal radiation

Article References: Zhang, L., Zhai, F., Wu, Y., Chang, S., Ye, Y., Lang, X., Pang, Y., Hu, L., Feng, Q., Forel, M.-B., Danelian, T., Yong, Y., & Vannier, J. (2026). Cuticular microfragments from the lower Cambrian Yanjiahe Formation, China: insights into ecdysozoan biodiversity at the dawn of animal radiation. Journal of Micropalaeontology, 45(1), 455-474. https://doi.org/10.5194/jm-45-455-2026

Image Credits: AI Generated

DOI: 10.5194/jm-45-455-2026

Keywords: Ecdysozoa, Cambrian explosion, Yanjiahe Formation, Fortunian Stage, phosphatization, Orsten-type preservation, panarthropods, scalidophorans, lobopodians, microfossils, South China, animal evolution

The team examined 10 outcrop sections spread across five regions of the Yangtze Platform: western Hunan, northeastern Guizhou, eastern Hubei, southern Shaanxi, and northern Sichuan. These strata, assigned to Cambrian Series 2 Stages 3 and 4, include both classic archaeocyath sponge reefs and quieter non-reefal carbonate settings. The scale of the work is staggering: 13,094 thin sections were prepared and scrutinized under a polarizing microscope, yielding more than 4,000 photomicrographs. Fossils were identified using diagnostic features such as filament diameter, length, branching pattern, sheath thickness, and overall morphology, with classifications cross-referenced against both fossil material and living cyanobacteria.

Among the headline discoveries are two new species: Streptubularia robustus, a robust curved tube with a thick micritic wall reaching external diameters of 85 to 125 micrometers, and Xianella mollis, an unbranched, wavy filament forming distinctive U-shaped mat-like bundles up to 3.3 millimeters long. The researchers interpret Xianella mollis as the calcified sheath of a cyanobacterium comparable to living Phormidiaceae such as Phormidium, whose modern bundles curve in strikingly similar ways. Streptubularia, by contrast, is compared with oscillatoriacean sheaths, though its sheer size and Y-shaped branching set it apart from better-known genera like Girvanella.

Perhaps the most consequential single finding concerns Acuasiphonoria, a genus of long, straight, needle-tipped filaments previously known only from Late Ordovician rocks of the Tarim Basin in northwest China. Its presence in the Qingxudong Formation of Hunan Province pushes the fossil record of this genus back roughly 40 million years, from the Late Ordovician into Cambrian Series 2. The study also reports the first occurrences in South China of six additional genera: Razumovskia, Subtifloria, Xianella, Bija, Botomaella, and Acuasiphonoria itself, substantially closing a biogeographic gap between the famously well-studied Cambrian floras of Siberia and the more fragmentary records elsewhere.

The systematic framework assigns the fossils to two cyanobacterial orders. Girvanella, Subtifloria, Razumovskia, Acuasiphonoria, Xianella, and Streptubularia belong to the Oscillatoriales, filamentous forms whose calcified sheaths tangle, bundle, or anastomose into cable-like strands. Kordephyton, Bija, Hedstroemia, and Botomaella are placed in the Nostocales, bushy, fan-like, radially branching forms resembling modern rivulariaceans such as Rivularia. The associated Microproblematica, including the dendritic Epiphyton, the chambered Renalcis, and the cleft-walled Izhella, remain of uncertain affinity, though some evidence, including direct indications of photosynthesis reported in earlier work, points toward a cyanobacterial or bacterial origin for at least some of them.

Why do these microbes calcify at all? The answer lies in their physiology. Cyanobacterial photosynthesis raises pH within and around the extracellular polysaccharide sheath, promoting the precipitation of calcium carbonate on or within the sheath itself. Because this process depends on seawater carbonate saturation state and atmospheric carbon dioxide levels, the abundance and diversity of calcified cyanobacteria through geological time can serve as a proxy for ancient ocean and atmosphere chemistry. Riding’s 1992 concept of cyanobacterial calcification episodes, or CCEs, formalizes this idea: intervals of enhanced marine cyanobacterial calcification alternate with episodes of reduced calcification, tracking secular shifts in the carbon cycle.

The Cambrian and Early Ordovician have long been recognized as major CCEs, and the new South Chinese data reinforce that picture with unprecedented regional detail. The assemblages from the Yangtze Platform closely resemble those of the Siberian Platform and North China, establishing that at least 15 genera of calcified cyanobacteria had achieved a genuinely global distribution in shallow marine waters by the early Cambrian. This is a striking contrast with North America and Europe, where early Cambrian calcified microfossil diversity is comparatively depauperate, commonly limited to Girvanella and Botomaella.

The study also reveals how these microbes built and organized ecosystems through time. During deposition of the Xiannüdong Formation in Stage 3, microbial-archaeocyath reefs developed, but calcified cyanobacteria were scarce, with Epiphyton and Renalcis merely encrusting sponge frameworks amid substantial terrigenous clastic input. In the Tianheban Formation of Stage 4, archaeocyaths still formed the reef skeleton, but calcified cyanobacteria such as Kordephyton, Streptubularia, and Bija took on important encrusting and binding roles. Then, when archaeocyaths went extinct, reefs in the Qingxudong Formation were constructed entirely by calcimicrobes, whose diversity and abundance surged. Filamentous mats reduced water flow and trapped sediment, while chambered Epiphyton and Renalcis clusters reinforced the framework and filled interstitial spaces, demonstrating a complete ecological handover from animals to microbes.

Notably, the research documents for the first time that calcified cyanobacteria flourished not only in reefs but also in non-reefal shallow-marine carbonate facies in South China, where they occur in low-energy settings, though in depauperate assemblages. The taxonomic composition tracks sedimentary environment closely, with diversity and abundance peaking in reefal facies whose character was set by the other reef builders present. The authors suggest that the gradual evolution from simple oscillatoriacean-dominated assemblages to more diverse communities including Phormidiaceae and Rivulariaceae may have been driven by ecological competition with archaeocyaths, by declining terrigenous detrital input, or by both factors together.

Beyond its taxonomic contributions, the study carries implications for understanding the dawn of the Phanerozoic Eon, the interval during which nearly all major animal phyla appeared. While the Cambrian explosion transformed animal life, the microbial world was undergoing its own quiet revolution, with calcifying cyanobacteria proliferating across reefs and open shelves alike. Because cyanobacterial calcification responds to atmospheric carbon dioxide and oceanic carbonate saturation, these fossil assemblages offer an independent window into the environmental conditions that accompanied the rise of complex animal ecosystems. The authors argue that continued study of these globally distributed floras will sharpen our understanding of cyanobacterial evolution, biogeography, and their environmental significance at one of the most pivotal moments in Earth history, when the chemistry of the oceans and atmosphere set the stage for half a billion years of animal-dominated life.

Subject of Research: Diversity and systematics of early Cambrian calcified cyanobacteria and associated microfossils in shallow-marine carbonates of the Yangtze Platform, South China

Article Title: Diversity and systematics of calcified cyanobacteria and associated microfossils in Cambrian Series 2 shallow-marine carbonates, Yangtze Platform, South China

Article References: Shen, J., Zheng, J., Liu, L., Wang, R., & Riding, R. (2026). Diversity and systematics of calcified cyanobacteria and associated microfossils in Cambrian Series 2 shallow-marine carbonates, Yangtze Platform, South China. Journal of Micropalaeontology, 45(2), 513-546. https://doi.org/10.5194/jm-45-513-2026

Image Credits: AI Generated

DOI: 10.5194/jm-45-513-2026

Keywords: calcified cyanobacteria, Cambrian Series 2, Yangtze Platform, South China, microfossils, cyanobacterial calcification episode, archaeocyath reefs, Girvanella, Acuasiphonoria, Microproblematica, paleoceanography, systematic paleontology

The research team, led by scientists at the Department of Geology of the University of Dhaka, collected 34 sediment samples along a land-sea transect spanning three environmentally contrasting areas: Cox’s Bazar on the eastern coast, Kuakata in the central deltaic zone, and the Sundarbans mangrove forest in the west. Sampling took place during winter, within the intertidal zone at elevations of roughly 0.5 to 4 meters above mean sea level, with cores extracted to a depth of 30 centimeters using a hand auger at low tide. Each sample was dried at 60 degrees Celsius for 24 hours, and 100-gram aliquots were sieved through meshes ranging from 63 to 1000 micrometers at one-phi intervals, following the Wentworth grain-size scale. Mean grain size and sorting were calculated using the Folk and Ward method.

The three study areas could hardly be more different. Cox’s Bazar, home to one of the longest natural beaches on Earth at 145 kilometers, is dominated by fine and medium sand, with fine sand reaching up to 75.1 percent of a sample and averaging 48.2 percent, while mud fractions are scarce. Kuakata displays a mixed picture: sediments at the Tin Nodir Mohona river mouth average 62.4 percent coarse sand, whereas the nearby Jhau Bon and Lebu Bon sites are rich in fine and very fine sand. The Sundarbans, the world’s largest mangrove forest covering roughly 6017 square kilometers, is a low-energy setting where fine and very fine sand dominate, averaging 59.5 and 27.2 percent respectively. These textural contrasts reflect fundamentally different hydrodynamic regimes, from wave-dominated open coast to tide-swept estuary to sheltered, freshwater-influenced mangrove plain.

When the researchers examined the foraminifera preserved in these sediments, the diversity patterns mapped almost perfectly onto the sediment map. Cox’s Bazar yielded 36 species across 26 genera, the highest diversity of the three areas, with Fisher’s alpha index ranging from 9.95 to 17.06 and Shannon values between 2.71 and 3.23. Kuakata produced 32 species from 20 genera with intermediate indices, while the Sundarbans assemblage contained only 19 species from 14 genera, the lowest diversity, with Fisher’s alpha falling as low as 4.89. The single most diverse site was Inani beach in Cox’s Bazar, and the least diverse was Kotka in the Sundarbans, a contrast that the authors link directly to substrate texture and the ecological conditions it implies.

The composition of the assemblages was equally revealing. The genera Ammonia and Elphidium dominated throughout the entire coastline, demonstrating their remarkable ecological tolerance, but each region carried a distinctive signature of companion taxa. Cox’s Bazar was characterized by Rotalinoides, Ammonia, Elphidium, and Asterorotalia, with mean relative abundances of 17.9, 17.4, 12.8, and 9.3 percent respectively. Kuakata was overwhelmingly dominated by Elphidium and Cribroelphidium at 33.8 and 20.7 percent, alongside several Ammonia species. In the Sundarbans, Ammonia reached individual-sample abundances of up to 55.6 percent, accompanied by Rosalina, Haplophragmoides, Entzia, Haynesina, and Trochammina, a suite of stress-tolerant and salt-marsh agglutinated forms typical of fine-grained, organically enriched, freshwater-influenced environments.

To test whether these patterns were statistically robust rather than coincidental, the team deployed a battery of complementary analyses. Spearman’s rank correlation across the combined 34-sample dataset showed that 18 of the 30 analyzed genera had at least one statistically significant association with a sediment fraction. Medium sand emerged as the fraction with the strongest biological signal: twelve genera, including Amphistegina, Spiroloculina, Cibicides, Rotalinoides, Neorotalia, and Operculina, showed significant positive correlations with it, while Ammonia, Elphidium, Rosalina, and Haplophragmoides were significantly and negatively correlated, reflecting their preference for finer substrates. The genus Gyroidella stood out as the only taxon significantly and positively correlated with coarse sand while being negatively correlated with both fine and very fine sand, marking it as a specialist of high-energy, coarse-grained settings.

Canonical correspondence analysis reinforced these findings in striking visual terms. The first two ordination axes together accounted for 90.9 percent of the constrained species-environment variance, with Cox’s Bazar samples aligning strongly with medium sands and Sundarbans samples clustering consistently with finer grains. Species vectors in the biplot closely tracked the sediment gradients, and the analysis independently reproduced the genus-substrate affinities identified by the correlation analysis. Finally, a two-way PERMANOVA based on Bray-Curtis dissimilarity and 9999 permutations confirmed that both location and sediment category significantly structured the assemblages, with p-values of 0.0001 and 0.0031 respectively. Crucially, the interaction term was not significant, meaning that sediment grain size exerts the same directional effect on community composition regardless of which of the three coastal environments is considered.

Why should grain size matter so much to organisms barely visible to the naked eye? The authors point to an indirect but well-supported mechanism: fine-grained sediments have greater surface area and adsorption capacity and are typically associated with higher organic matter concentrations, which in turn can deplete oxygen in the uppermost sediment layer. Although organic matter and dissolved oxygen were not directly measured in this study, a limitation the authors openly acknowledge, the dominance of opportunistic and stress-tolerant taxa such as Ammonia, Elphidium, and agglutinated forms in the Sundarbans is consistent with assemblages known from organically enriched coastal settings worldwide. The reduced diversity there likely reflects these stressed conditions, where a few tolerant species outcompete the rest.

The assemblages also encode hydrodynamic history. At Inani beach in Cox’s Bazar, the researchers found transported planktonic foraminifera, including Globigerina bulloides and Hantkenina alabamensis, species that live in the open water column and could only arrive on the beach through active wave and tidal transport. Their presence signals a well-connected, open-marine setting characteristic of the inner to middle neritic zone, rather than evidence of local productivity. In Kuakata, the combination of Elphidium, Cribroelphidium, Ammonia, and various miliolids, together with the complete absence of planktonic species, points to estuarine to very inner neritic conditions. In the Sundarbans, salt-marsh agglutinated foraminifera such as Trochammina inflata, Miliammina, Haplophragmoides, and Entzia were confined to areas under strong freshwater influence, echoing ecological patterns reported from karstic coasts of the Adriatic.

Beyond its scientific interest, the study carries practical weight for a coastline facing mounting natural and anthropogenic pressures, from sea-level rise to pollution and sediment starvation. By establishing sediment texture as a tractable, measurable, and directly comparable control on foraminiferal diversity, the work provides a framework for using these microfossils as bioindicators in environmental assessment. The authors recommend that future investigations incorporate direct measurements of organic matter, dissolved oxygen, salinity, and sediment mineralogy to refine the picture. For now, the message from the northern Bay of Bengal is clear: the grains on the seafloor, and the energy that arranges them, set the rules by which life at the smallest scale thrives or struggles, and reading those grains through the lens of foraminifera offers a powerful window into the health of coastal ecosystems under change.

Subject of Research: Relationship between sediment grain size and benthic foraminiferal diversity across contrasting coastal environments of Bangladesh

Article Title: Spatial patterns of benthic foraminiferal diversity in relation to sediment type across contrasting coastal environments of Bangladesh

Article References: Al Kabir, M. S., Saha, S. K., Tushar, M. A. N., & Maria, R. S. (2026). Spatial patterns of benthic foraminiferal diversity in relation to sediment type across contrasting coastal environments of Bangladesh. Discover Geoscience, 4(1), Article 344. https://doi.org/10.1007/s44288-026-00712-1

Image Credits: AI Generated

DOI: 10.1007/s44288-026-00712-1

Keywords: benthic foraminifera, sediment grain size, Bay of Bengal, Bangladesh coast, Sundarbans, Cox's Bazar, Kuakata, PERMANOVA, canonical correspondence analysis, coastal biomonitoring, microfossils, Ganges-Brahmaputra-Meghna delta

The mystery at the centre of the study is a familiar one to palaeontologists. Animals appear relatively suddenly in the fossil record just before the Cambrian Period, which ran from 539 to 487 million years ago, yet a growing body of indirect evidence suggests their evolutionary history began much earlier. Molecular clock analyses, which compare genetic differences between living species and work backwards using fossil dates as calibration points, have repeatedly hinted at a deep pre-Ediacaran origin. But many recent studies have constrained those estimates using a seemingly straightforward argument drawn from the fossil record itself, and it is precisely that argument which the new work dismantles.

The argument hinges on an exceptionally well-preserved fossil deposit in China known as the Weng’an Biota, found in rocks of Ediacaran age and dated to roughly 590 million years ago. The Weng’an Biota preserves microscopic organisms in extraordinary cellular detail, yet none of the fossils it contains can be definitively identified as animals. Researchers have therefore inferred that the first animals must have originated after Weng’an, reasoning that a deposit capable of preserving such delicate structures would certainly have captured animal embryos or larvae if animals existed at the time. In effect, Weng’an has been treated as a maximum age constraint, a hard ceiling on how old animals could possibly be.

The Oxford-led team, which included researchers from the University of California Berkeley, ETH Zürich and Yale University, tested that logic by surveying a younger deposit with comparable preservation quality: the Kheseen Biota of Mongolia. The Kheseen Biota is more than 40 million years younger than Weng’an, yet the two deposits share some species, and by the time Kheseen was laid down animal fossils were already known from sites elsewhere in the world, including Namibia and South China. The researchers examined more than 140 samples, some from previously undocumented localities, using scanning electron microscopy to resolve fine anatomical detail at the microscopic scale.

The results were striking. The Mongolian material yielded exquisite new microfossil species, including acritarchs, tiny spherical organisms adorned with spines and branching projections, as well as embryo-like fossils preserving internal cells. The quality of preservation rivals anything seen in the Ediacaran record. Yet despite this remarkable fidelity, not a single specimen could be confidently assigned to the animal kingdom. Animals were demonstrably alive when the Kheseen Biota formed, but they left no trace within it, a direct contradiction of the preservation-based reasoning applied to Weng’an.

Senior author Associate Professor Ross Anderson of the Museum of Natural History at Oxford University explained the significance of the finding. The Kheseen Biota, he said, breaks the argument that the exceptional microfossils of Weng’an mean animal fossils would have been seen in the assemblage had they existed at the time. The Kheseen microfossils are just as well-preserved, yet animals continue to be absent, despite the fact that they are known to have existed by that point. The most plausible explanation is that early animals lived in environments different from those that preserved the Kheseen fossils, or that the local chemical conditions after death simply failed to preserve animal remains.

With the Weng’an ceiling removed, the team rebuilt their molecular clock analyses using much older geological constraints. They turned to fossil-rich deposits dating from roughly 850 to 730 million years ago, including the Svanbergfjellet Formation in Norway, the Bitter Springs Group in Australia and the Chuar Group in Arizona. These deposits have the potential to preserve animals even though definitive animal fossils have eluded discovery within them, and they have previously served as maximum dates for animal origins in other studies. When the molecular clock was anchored to these older formations rather than to the Ediacaran Weng’an deposit, the estimated origin of animals shifted backwards by around 200 million years, landing between 800 and 700 million years ago.

That timeline is not without independent support. Chemical fossils, known as biomarkers, preserved in ancient rocks provide evidence consistent with sponges living at least 650 million years ago, tens of millions of years before the oldest definitive macroscopic animal fossils appear. The molecular clock estimate also raises a provocative possibility: animals may already have evolved before Earth entered the Cryogenian glaciations, or even emerged during that inhospitable interval. The Cryogenian Period began around 720 million years ago, when enormous glaciers spread across the planet in episodes commonly known as Snowball Earth. The new study reopens the question of whether the dramatic environmental conditions associated with those global ice ages played a role in the origin and early evolution of animal life, a possibility that had been closed off under the younger Ediacaran timeline.

First author Orin Lole Durbin, who conducted the work as an undergraduate at Oxford and is now at Virginia Tech, cautioned that the analysis does not prove animals existed 800 million years ago. Pre-Ediacaran animal body fossils still elude researchers, and the molecular clock provides an estimate rather than a direct observation. However, the new fossil evidence from Mongolia undermines one of the main arguments for restricting animal origins to the Ediacaran interval, while the molecular-clock analyses show how much further back their evolutionary history could extend. The distinction matters: the study does not claim to have found ancient animals, but it removes a key obstacle to the idea that they existed far earlier than the rocks currently reveal.

Part of the reason early animals remain so elusive lies in their biology. The first animals would have been small and soft-bodied, lacking the shells, bones and other hard structures that make later animals so much easier to fossilise. Whether such creatures were preserved at all depended on their environment and on an unusual combination of chemical conditions after death, conditions that evidently failed in the Kheseen setting even as exquisite microfossils of other organisms formed. The researchers argue that future work should therefore explore fossil deposits from different parts of the world, representing different environments and modes of fossilisation, in the search for animals. Such searches should also weigh all available lines of evidence, including body fossils, traces of animal activity and chemical biomarkers, rather than relying on any single signal. Until that evidence becomes available, as Anderson noted, the precise birth date of the animal kingdom remains uncertain, but the window of possibility has now swung dramatically open toward the deep Neoproterozoic.

Subject of Research: Re-evaluating fossil calibration constraints on the molecular clock timing of animal origins

Article Title: New study suggests animals may have evolved vastly earlier than fossil evidence suggests

Article References: New study suggests animals may have evolved vastly earlier than fossil evidence suggests. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: animal origins, molecular clock, Ediacaran, Neoproterozoic, Weng'an Biota, Kheseen Biota, Snowball Earth, Cryogenian, microfossils, sponges, Cambrian explosion, fossil record