The investigators combined terms for bone or skeletal metastasis with artificial intelligence and related methods, including machine learning, deep learning, radiomics, computer vision, computer-aided diagnosis, neural networks, support vector machines, random forests, image segmentation and large language models. The databases initially returned 1,756 records: 495 from Web of Science, 424 from PubMed and 837 from Scopus. After hierarchical removal of 832 duplicates, 924 unique records underwent title-and-abstract screening by two reviewers, with a third resolving uncertain cases. Another 384 records were excluded, leaving 540 publications. R, VOSviewer and CiteSpace were used to examine annual trends, journals, countries, institutions, authors, citation bursts, keyword co-occurrence, collaboration networks and thematic evolution.

Annual output was limited before 2020 and then rose sharply, producing an overall annual growth rate of 24.01%. The cumulative total rose from 61 publications in 2019 to 540 by the retrieval date, with 101 publications in 2025, the most recent complete calendar year. Seventy-four papers had been included by June 26, 2026, so this partial-year figure should not be compared directly with complete years or interpreted as a decline. The publications involved 3,439 authors, 1,118 author keywords and 16,020 references. The mean publication age was 3.46 years, the average was 10.06 citations, and publications had 8.13 coauthors on average. International coauthorship accounted for 19.63% of the dataset.

China was the largest national contributor, with 233 publications, followed by Japan and the United States with 51 each. Italy produced 19 papers, South Korea 18, Canada 15, Germany 14 and the Netherlands 13. The collaboration network centered on China, the United States, Japan, Italy and South Korea, with additional links among European research groups. Contributions from Africa, South America and parts of Central Asia were limited. China had 204 single-country and 29 multiple-country publications; Japan had 44 and seven, while the United States had a more balanced split of 31 and 20. These results describe the structure of scholarly cooperation, not the quality, generalizability or clinical effectiveness of models developed in any country.

Institutional output was concentrated in several collaborative hubs rather than one fully integrated global network. Northwest Minzu University contributed 64 publications, China Medical University 47, Harvard University 34 and Harvard University Medical Affiliates 31. China Medical University in Taiwan, National Taiwan University and the University of Toronto each produced 28. Network maps identified connections among Chinese institutions and international partners, a separate cluster centered on Harvard Medical School and Massachusetts General Hospital, and smaller groups involving Lund University, the University of Gothenburg, Sahlgrenska University Hospital and institutions in Taiwan. Among authors, Cao YC had 22 publications, Lin Q 21 and Zeng XW 20, while Edenbrandt L had 353 total citations and 96 local citations from 10 publications.

Citation-burst analysis traced a shift in the references attracting attention. The strongest burst, with a strength of 7.69 from 2013 to 2017, was associated with computer-aided diagnosis of bone scintigrams. A review of deep learning in medical image analysis registered a burst strength of 6.42 during 2020–2021, and two deep-learning studies of bone-metastasis classification remained active from 2021 to 2023. The most locally cited work was a 2021 global cancer statistics paper with 46 local citations. The foundational U-Net paper and a study of computer-assisted interpretation of whole-body bone scans each received 41 local citations. Such citation patterns map attention to research themes but do not rank individual methods by clinical effectiveness, methodological rigor or readiness for implementation.

Keyword networks separated the literature into four broad themes: bone metastasis with prognostic and treatment assessment; deep learning, bone scintigraphy and computer-aided diagnosis; prostate cancer with MRI and PET/CT; and broader methods involving convolutional neural networks, segmentation and natural language processing. Bone metastasis was the most frequent author keyword, appearing 216 times, followed by machine learning with 106, deep learning with 103, radiomics with 69, prostate cancer with 68, artificial intelligence with 57 and bone scintigraphy with 51. The chronology mapped an early emphasis on computer-aided diagnosis and quantitative skeletal assessment, followed by deep-learning image analysis, predictive modeling and cancer-specific applications. Prostate cancer formed a sustained branch, whereas research concerning breast-cancer bone metastasis remained comparatively smaller.

Language-based AI appeared only as a limited extension beyond conventional imaging applications. Recent studies used fine-tuned or general-purpose language models to structure radiology reports, extract electronic-health-record variables, assemble cohorts and provide accessible information about bone metastasis and cancer-induced bone pain. In a Chinese multicenter workflow, clinical-logic-guided prompting reduced manual processing time by 74.5%–82.6% while supporting an atlas of 18,331 patients. Another study reported an accuracy of 0.85 for extracting bone-metastasis status from electronic health records with Llama 3.1 8B. These studies demonstrate feasibility for particular information-processing tasks, not autonomous clinical decision-making, and their performance cannot be directly compared because datasets, validation strategies and outcome definitions differed.

The analysis identified data heterogeneity, limited external validation, reproducibility concerns and insufficient prospective evidence as barriers to clinical translation. Most systems address specific tasks such as detection, segmentation, classification, risk prediction or outcome estimation, and many are evaluated with retrospective datasets. Transferring such systems to other hospitals may expose them to differences in scanners, acquisition protocols, reconstruction settings, radiotracers, patient populations and clinical workflows. Retrospective cohorts can also underrepresent some cancers, stages or healthcare settings, while variations in reference standards and annotation procedures can introduce measurement bias. The authors emphasize representative multicenter datasets, transparent reporting of cohort selection and annotation, and evaluation across clinically relevant subgroups.

Prospective evaluation would need to assess more than accuracy, area under the curve or segmentation scores. Relevant measures include calibration, clinical utility, workflow effects and meaningful patient outcomes, alongside the stability of performance across institutions and time. The dataset itself also has limitations: relevant studies outside the three databases or excluded by the English-language restriction may have been missed; network maps depend on term normalization, thresholds and clustering choices; citation indicators favor older publications; and the 2026 record covers only January 1 through June 26. Most importantly, the bibliometric study maps research activity and themes rather than directly comparing model quality or clinical performance. Its central finding is that AI publication activity in bone metastasis is growing quickly, imaging still dominates, and language-based research remains early and limited.

Subject of Research: Bibliometric analysis of artificial intelligence applications in bone metastasis research

Article Title: Mapping the evolution of artificial intelligence applications in bone metastasis: a bibliometric and visualization analysis

Article References: Lin, Y., Ye, S., Wu, J., Hu, Y., Wu, H., He, H., Yang, J., Wang, Y., Ni, B., Zhu, L., Ding, C., Liu, C., Musaev, E. R., Wang, J., Zhang, C., & Zheng, M. (2026). Mapping the evolution of artificial intelligence applications in bone metastasis: a bibliometric and visualization analysis. Frontiers in Oncology, 16, Article 1971840. https://doi.org/10.3389/fonc.2026.1971840

Image Credits: AI Generated

DOI: 10.3389/fonc.2026.1971840

Keywords: bone metastasis, artificial intelligence, bibliometric analysis, medical imaging, deep learning, radiomics, clinical language models, oncology, prognostic modeling, research collaboration, Mapping, evolution

The researchers focused on the beetle genus Onthophagus, which includes species with sex- and nutrition-responsive horns used as secondary sexual weapons in reproductive competition. By comparing the gene-regulatory properties of horns in two closely related species with highly specialized, condition-biased phenotypes, the study examined how regulatory DNA may evolve alongside traits that respond to sex and nutrition.

The analysis identified mutational accumulation across species, condition-specific changes in chromatin accessibility within species, and the acquisition of lineage-specific regulatory elements. Many of the putative regulatory regions contained binding-site motifs associated with members of the bone morphogenetic protein signaling pathway, including developmental regulators. The authors also reported functional evidence that two proteins in this pathway had been co-opted for horn development and that their activity influenced horn shape and size across species, sexes and nutritional states.

Together, the results support a model in which evolutionarily labile cis-regulatory interactions modify the activity of conserved developmental pathways over short evolutionary timescales. The study is limited to the regulatory and functional analysis of horns in two beetle species, so it does not establish the same mechanism for horn diversification across the wider genus or for other condition-responsive traits. Its central finding is an association between regulatory evolution and trait diversification, supported by functional evidence for two bone morphogenetic protein pathway proteins.

Subject of Research: Comparative analysis of regulatory evolution and BMP signaling in horn diversification in Onthophagus beetles.

Article Title: The role of gene regulatory evolution in weapon diversification: Insights from comparative genomics, chromatin profiling, and functional analyses of BMP signaling in horned beetles

Article References: Davidson, P. L., Manley, I. G., & Moczek, A. P. (2026). The role of gene regulatory evolution in weapon diversification: Insights from comparative genomics, chromatin profiling, and functional analyses of BMP signaling in horned beetles. PLOS Genetics, 22(10), e1012338. https://doi.org/10.1371/journal.pgen.1012338

Image Credits: AI Generated

DOI: 10.1371/journal.pgen.1012338

Keywords: Onthophagus beetles, horn diversification, cis-regulatory evolution, chromatin accessibility, BMP signaling, comparative genomics, developmental pathways, sexual selection, role, gene, regulatory, evolution

The researchers used repacked columns to represent the upper 30 centimeters of soil, preserving material from the original 0–10, 10–20 and 20–30-centimeter depth intervals rather than mixing them together. Each column was compacted to a dry bulk density of 1.28 grams per cubic centimeter. The experimental design crossed two soil types, three nominal initial-moisture regimes and five freeze-thaw totals of 1, 3, 5, 10 and 15 cycles, with three replicate columns for every combination. Each 24-hour cycle consisted of 12 hours at minus 20 degrees Celsius followed by 12 hours of thawing at room temperature. The outer surface of each column was sealed during cycling to reduce evaporative moisture loss.

The two soils came from the same seasonally frozen region but had markedly different chemical properties. The saline soil had a pH of 9.37, total salinity of 0.27% and an exchangeable sodium percentage of 20.30%. The non-saline counterpart had a pH of 7.67, salinity of 0.04% and an exchangeable sodium percentage of 0.10%. Their carbonate and bicarbonate concentrations and cation exchange capacities also differed. As a result, the study treated comparisons between the soils as differences in the overall saline-soil chemical background, which included salinity, alkalinity and sodicity. The analysis did not isolate total salinity as the only cause of those differences.

After each prescribed freeze-thaw treatment, every column was vacuum-saturated with deionized water before low-field nuclear magnetic resonance measurement. This procedure standardized the amount of liquid pore water across treatments and allowed the researchers to compare the structures that remained after freezing and thawing. It also limits the interpretation: vacuum saturation can dissolve and redistribute soluble salts, so the resulting spectra do not directly represent the in situ water-salt distribution during a freeze or thaw. The measurements are indirect indicators of pore structure under a common saturated condition, not direct images of cracks, pore geometry or connectivity.

In low-field NMR, hydrogen nuclei in pore water produce a signal whose transverse relaxation time, T2, is controlled mainly by interactions with pore surfaces. Under surface-relaxation conditions, shorter T2 values are associated with smaller pores, whereas longer values are associated with larger pores. The researchers divided the T2 distributions into micropore, mesopore and macropore domains corresponding to 0.1–10, 10–100 and 100–1,000 micrometers. Because surface relaxivity was not independently calibrated using mercury intrusion porosimetry, X-ray computed tomography, gas adsorption or image analysis, these categories were interpreted as relative NMR-derived pore-size domains rather than exact measurements of pore diameter.

The averaged T2 spectra from both soil types were dominated by a main peak between approximately 0.1 and 100 milliseconds, showing that the detected water signal was concentrated mainly in micro- and mesopore domains. Some treatments also displayed a weaker shoulder or secondary peak at longer relaxation times, indicating a smaller contribution from larger-pore domains. In saline soil at low moisture, a weak long-T2 component became more evident after the first cycle and then weakened with further cycling. Under medium and high moisture, the saline soil’s long-relaxation-time signal generally declined as cycling progressed. The non-saline soil retained its long-T2 component more consistently, particularly at high moisture, although the main peak positions in the two soils remained broadly similar.

Standardized path analysis identified moisture content as the variable with the largest relative contribution to variation in the NMR-derived pore-size fractions, accounting for 56.0% of the variation within the variables examined. Soil depth contributed 21.3%, the number of freeze-thaw cycles 11.4% and the salinity indicator 11.3%. Moisture was negatively associated with microporosity, with a standardized coefficient of minus 0.655, and positively associated with mesoporosity at 0.694. Its positive association with macroporosity was smaller, at 0.296. The separate models explained 50.0% of microporosity variation, 51.5% of mesoporosity variation and 32.5% of macroporosity variation, indicating moderate explanatory performance for the first two fractions and more limited performance for the largest-pore category.

Cycle number and the salinity indicator had weaker and more selective associations than moisture. The number of cycles was negatively associated with macroporosity, with a standardized coefficient of minus 0.210, while its small positive association with microporosity was not statistically significant. Salinity was not significantly associated with either microporosity or mesoporosity, but it was negatively associated with macroporosity at minus 0.246. At high moisture, macroporosity increased in the non-saline soil but remained relatively low in the saline soil across the cycle sequence. Soil depth was positively associated with microporosity at 0.226 and negatively associated with mesoporosity at minus 0.198 and macroporosity at minus 0.215. The relatively low explanatory value for macroporosity leaves room for unreported influences such as local packing variability, slight compaction differences, aggregate fragmentation and the formation or collapse of isolated large pores.

The pore-water fractal dimension, Dw, provided a complementary description of multi-scale heterogeneity in the T2 distributions. Values ranged from approximately 1.67 to 2.67 across all treatments. Under low moisture, Dw remained between 1.67 and 1.79 in both soils and fluctuated only slightly as the number of cycles increased. Under medium and high moisture, it was generally higher, spanning roughly 2.17–2.67, consistent with the pore-water signal being distributed across a wider range of size domains. At high moisture, Dw in the saline soil stayed within 2.18–2.29 without a clear monotonic trend, whereas the non-saline soil ranged from 2.53 to 2.67 and reached about 2.58 after 15 cycles. After cycling, the positive correlation between moisture and Dw became stronger, salinity showed a negative correlation and cycle number showed only a weak negative relationship. These correlations were descriptive and were not treated as causal paths.

Moisture and salinity followed distinct trajectories through the treatments. In saline soil, mean moisture under the low-moisture condition declined from 0.045 to 0.032, while the medium-moisture treatment rose from 0.250 to 0.295. The high-moisture treatment remained between 0.310 and 0.320. In non-saline soil, low moisture stayed near 0.065, while the medium and high treatments declined to 0.205 and 0.260, respectively. Salinity in the saline soil rose to approximately 0.33–0.36% after one to three low-moisture cycles and then declined slightly, remaining above its initial value. Under wetter conditions, salinity decreased during the early cycles, reached a relatively low level around five cycles and rose again with additional cycles. The non-saline soil remained within 0.015–0.045% throughout. Overall, the measurements associate the initial freeze-thaw event and moisture condition with the clearest pore-structure responses, while the indirect, saturated-state NMR method limits conclusions about field-scale salt movement and actual pore connectivity.

Subject of Research: Associations among moisture, freeze-thaw cycling and NMR-derived soil pore structure

Article Title: Moisture–dependent evolution of NMR–derived pore structure in saline and non–saline soils during freeze–thaw cycles

Article References: Qiu, Y., Gu, Z., Nie, S., & Zou, Y. (2026). Moisture–dependent evolution of NMR–derived pore structure in saline and non–saline soils during freeze–thaw cycles. Environmental Earth Sciences, 85(17), Article 436. https://doi.org/10.1007/s12665-026-13095-w

Image Credits: AI Generated

DOI: 10.1007/s12665-026-13095-w

Keywords: saline soils, freeze-thaw cycles, soil moisture, low-field NMR, pore-size distribution, pore-water fractal dimension, seasonally frozen ground, path analysis, Jilin Province, Moisture, dependent, evolution

The experiment examined how the LPSO-dominated material responded to increasing equivalent strain under high-pressure torsion. High hydrostatic pressure and intense shear deformation induced numerous kink bands within the LPSO phase. As equivalent strain increased, the fraction of high-angle kinks rose continuously.

Portions of the ordered phase were also refined through two observed fragmentation modes: blocky fragmentation and delamination tearing. Alongside the changes within the LPSO phase, severe plastic deformation generated a high density of dislocations. Numerous dislocation substructures formed as strain increased, with initially tangled dislocations gradually becoming more organized.

The observed configurations included dislocation cells and dislocation walls. Regularly arranged dislocation walls subsequently developed into lamellar boundaries. The reported hardness gains were associated with the combined effects of dislocation strengthening and kink strengthening, rather than with a single microstructural mechanism.

The alloy also exhibited a strain-hardening exponent of 0.09, which the researchers described as excellent in comparison with conventional magnesium alloys. The results are limited to a laboratory Mg-18Y-8Ni alloy processed by high-pressure torsion at room temperature, and the principal mechanical measure reported is microhardness. The study does not establish whether the same response will occur in large components or persist under service conditions.

Its central result is a measured connection between increasing deformation, the formation of high-angle kinks and fragmented LPSO regions, the development of organized dislocation structures, and increased microhardness in this LPSO-dominated magnesium alloy.

Subject of Research: Microstructural evolution and strengthening of an LPSO-dominated magnesium alloy during high-pressure torsion

Article Title: Evolution of microstructure and mechanical properties of LPSO-dominated Mg-18Y-8Ni (wt.%) processed via high-pressure torsion

Article References: Yin, R. R., Qiao, X. G., Enikeev, N. A., Valiev, R. Z., & Zheng, M. Y. (2026). Evolution of microstructure and mechanical properties of LPSO-dominated Mg-18Y-8Ni (wt.%) processed via high-pressure torsion. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13966-4

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13966-4

Keywords: high-pressure torsion, magnesium alloy, LPSO phase, microstructure, microhardness, kink bands, dislocations, strain hardening, severe deformation, materials science, Evolution, mechanical

The researchers investigated the alloy using hot uniaxial compression tests at 350–450 °C and strain rates of 0.01–1 s⁻¹. They also conducted strain-rate-jump compression tests to examine the influence of loading-rate history. These were laboratory deformation experiments on one spray-formed alloy; the available abstract does not describe replication, uncertainty estimates or the number of specimens tested.

According to the abstract, subgrain rotation driven by dynamic recovery and deformation was identified as the principal mechanism of continuous dynamic recrystallization. Three forms of low-angle grain boundaries were observed: equiaxed subgrain structures, and low-angle boundaries with preferred orientations either parallel to the compression direction or perpendicular to it. The reported orientations were also associated with grain orientation.

The strain-rate-jump tests showed an asymmetric response in flow stress and microstructure evolution to loading history, which the abstract describes as observed for the first time in hot deformation of Al–Zn–Mg–Cu alloy. The authors suggest that dislocation accumulation and the time available for rearrangement through dynamic recovery may contribute to differences from constant-strain-rate uniaxial compression. The available summary does not provide the magnitude of the flow-stress changes, quantitative texture data, detailed boundary statistics or full methodological information, so the scope of these findings is limited to the reported abstract rather than an assessment of the complete article.

Subject of Research: Hot-deformation microstructure and continuous dynamic recrystallization in spray-formed Al–Zn–Mg–Cu alloy

Article Title: Microstructure evolution and dynamic recrystallization of spray-formed Al–Zn–Mg–Cu alloy under hot deformation

Article References: Tao, L., Zhang, Z., Jia, W., Sun, C., Li, D., Jia, Z., & Zhou, G. (2026). Microstructure evolution and dynamic recrystallization of spray-formed Al–Zn–Mg–Cu alloy under hot deformation. Journal of Materials Science, 61(43), 33974-33994. https://doi.org/10.1007/s10853-026-13710-y

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13710-y

Keywords: Al–Zn–Mg–Cu alloy, spray-formed alloy, hot deformation, continuous recrystallization, dynamic recovery, uniaxial compression, strain-rate history, microstructure evolution, texture intensity, grain boundaries, Microstructure, evolution

According to the study abstract, TE4 integrates resistance, recovery, adaptive capacity, and institutional learning and preparedness. Its non-compensatory structure is intended to prevent strong performance in one dimension from offsetting weakness in another. A traditional composite index increased by 5.09% between the 2014 and 2024 endpoints, while the model’s adaptive-capacity component increased by 29.38%. TE4 component estimates indicated that potential resilience rose by 9.28%, while recovery capacity fell by 8.03%. The modeled unrealized resilience gap widened by 15.67%, which the authors described as indicating a recovery-related conversion deficit.

Removing indicators derived from the Normalized Difference Vegetation Index barely changed TE4 rankings, with a Spearman correlation coefficient of 0.983. Panel models did not show short-term net primary productivity buffering associated with higher TE4 under stronger drought. Pre-event recovery capacity had the strongest positive, but statistically inconclusive, association with post-drought net primary productivity recovery.

The abstract presents TE4 as a structural diagnostic tool for identifying capacity deficits and prioritizing recovery-oriented disaster risk reduction, rather than as a direct predictor of annual ecosystem productivity. The evidence supplied here is limited to the abstract, so the study’s full methods, results and limitations could not be independently assessed.

Subject of Research: Model-based assessment of structural urban resilience in dryland oasis units

Article Title: Structural diagnosis and evolution of urban resilience in dryland oasis urban agglomerations from an eco-immunological perspective

Article References: Hou, Y., Hu, Q., & Halik, Ü. (2026). Structural diagnosis and evolution of urban resilience in dryland oasis urban agglomerations from an eco-immunological perspective. Scientific Reports. https://doi.org/10.1038/s41598-026-75595-w

Image Credits: AI Generated

DOI: 10.1038/s41598-026-75595-w

Keywords: urban resilience, dryland oases, Tianshan Mountains, TE4 model, adaptive capacity, recovery capacity, drought, net primary productivity, ecosystem productivity, Structural, diagnosis, evolution

Plesiosaurs were globally distributed predatory marine reptiles with short torsos, short tails, four large flippers, and skulls and necks that varied greatly in proportion. Long-necked, small-headed plesiosauromorphs and short-necked, large-headed pliosauromorphs occupy opposite ends of this morphological range. The great variation in neck and skull architecture has made it particularly important to distinguish genuine juveniles from reproductively mature animals that retain juvenile-looking bones. A specimen with unfused neural arches, an unfaceted distal propodial or incompletely fused girdle elements may be young, but the same external condition can persist in a sexually mature animal when paedomorphism is present. A fossil’s external appearance therefore cannot by itself establish its biological age or reproductive status.

Most assessments of plesiosaur maturity have followed the Brown model, developed from ontogenetic sequences of the cryptoclidids Cryptoclidus and Muraenosaurus in the Oxford Clay Formation of the United Kingdom. In its original tripartite form, the model labels specimens with separate neural arches and centra as juveniles, those with fused centra and arches but a visible neurocentral suture as adults, and those with completely obliterated sutures as old adults. This sequence is based on osteological maturity rather than directly observed sexual maturity, yet its labels have commonly been treated as equivalent to juvenile, adult and old adult. The broader application of the model creates three problems: skeletal and sexual maturity need not occur together, different parts of the skeleton may ossify at different rates, and growth patterns documented in cryptoclidids may not apply across every plesiosaur lineage.

Paedomorphism describes the retention of an ancestrally juvenile condition in a descendant that has reached maturity. It can arise through different heterochronic processes, including slower growth, early completion of development or delayed onset of particular traits. In fossils lacking reliable developmental-rate data, sequence heterochrony provides a more practical framework for identifying traits whose onset, offset or completion differs from the ancestral condition. Plesiosaurs also inherited paedomorphic features from earlier sauropterygians, including incomplete neurocentral fusion, reduced numbers of carpal or tarsal elements and, in some groups, the absence of a calcified sternum. The analytical challenge is therefore to distinguish primitive skeletal conditions, individual immaturity and mature retention of juvenile anatomy. The study addresses this by analyzing maturity frequencies rather than attempting to assign exact developmental mechanisms to every specimen.

For the temporal analysis, the researchers divided the interval from 234.55 million years ago, in the Early Carnian, to 66 million years ago, in the Late Maastrichtian, into geological time bins. They calculated the ratio of osteologically immature specimens, I, to the combined number of partially and fully mature specimens, P and M, using I/(P+M) as a proxy for paedomorphism. Four bin widths were examined, including 4.5-million-year intervals selected as the narrowest scheme that reduced gaps in the record. Linear regressions were statistically significant for the 2-million-year bins, with p = 0.001, and the 6-million-year bins, with p = 0.015. The corresponding p-values for the 4.5- and 10-million-year schemes were 0.095 and 0.065, so these results did not meet the conventional 5 percent significance threshold even though the direction of the trend remained upward.

Nonlinear and non-parametric analyses also recovered an overall increase in I/(P+M). Linear models were among the best-fitting approaches, while nonlinear models included exponential growth, beta growth, Michaelis–Menten and third-order polynomial functions. The third-order polynomial described a sharp increase until the end of the Jurassic, relative stabilization during the Early Cretaceous and a marked later increase toward the Cretaceous–Paleogene boundary. LOWESS smoothing, which relaxes the assumption of a fixed linear relationship, produced a broadly similar upward trajectory. The authors estimated the rate of paedomorphic evolution across Plesiosauria as a whole at 0.6% per million years, with 95% confidence bounds of 0.3–0.9% per million years. This is a gradual estimated change, contrasting with the reportedly rapid acquisition of a broadly paedomorphic body plan in phocoenid cetaceans within less than about 11 million years.

Clade-level patterns were heterogeneous, demonstrating that the aggregate trend cannot be reduced to a single family-wide transformation. The superfamily Pliosauroidea showed an increase from an I/(M+P) ratio of about 0.2 in the Early Jurassic to around 1 in the Middle Jurassic and Early Cretaceous. Polycotylidae showed a stronger rise: immature and partially mature specimens together represented about 75% of the sample, and the ratio reached roughly 4 by the end of the Cretaceous, meaning about four immature specimens for every partially or fully mature specimen combined. Cryptoclididae also showed an increasing tendency, with only about 27% of the 88 specimens fully mature. Elasmosauridae generally had about one immature specimen for every partially or fully mature specimen, without a significant temporal trend. Among only 22 rhomaleosaurids, 95.2% were immature or partially mature, although the group’s short range and small sample prevent a broad evolutionary inference.

The most conspicuous local pattern was an Early Aptian outlier. Under the 4.5-million-year bin scheme, the mean I/(M+P) ratio was 0.40 before the Aptian and 0.83 afterward, but the Aptian value reached 3.0. Most specimens contributing to this peak had been assigned to the elasmosaurid Woolungasaurus glendowerensis and were osteologically immature. The authors identify the Aptian–Albian as a period of poor sampling, making it possible that the apparent peak reflects uneven collecting or the influence of one abundant taxon rather than a distinct biological episode. More specimens from the interval could either weaken or strengthen the observed outlier. The same caution applies to proposals that concentrations of immature plesiosaurs represent coastal nurseries, because those interpretations assume the individuals were both ontogenetically and sexually immature rather than mature animals exhibiting paedomorphism.

Bone histology offers an independent way to test that assumption because internally mature tissues can contradict juvenile-looking external anatomy. Published sections of Angolan aristonectines combine small, unfaceted propodials, flat vertebral articular surfaces, unfused neural arches and weakly developed girdle elements with secondary osteons, remodeled periosteum and three lines of arrested growth. One interpretation is paedomorphism; another is that the proposed histological juvenile and adult categories need revision. The available evidence remains too sparse for a comprehensive test because plesiosaur histology has not been surveyed systematically across taxa and growth stages, and samples only centimetres apart in a single bone can show very different structures. The researchers therefore argue that ontogenetic assessments should remain hypothetical until supported by paleohistological data, and they recommend replacing labels that imply sexual maturity with the strictly anatomical categories osteologically immature, partially osteologically mature and osteologically mature.

Uneven fossil representation remains a central limitation. The Early Cretaceous represented about 33% of plesiosaur longevity but supplied only around 11% of specimens in the database, whereas the Late Cretaceous contributed about 37% of specimens across roughly 25% of the group’s history. Some intervals and clades therefore remain poorly represented, and the ratio is sensitive to taxonomic assignments, sampling intensity and the inclusion of partially mature specimens in the denominator. The fossil record also preserves no direct evidence of fertility for most specimens, and the study does not establish whether each immature-looking individual was reproductively mature. Even with these limitations, the analyses consistently identify a broad shift toward a higher relative abundance of osteologically immature material in later plesiosaur history. The result challenges the automatic classification of juvenile-looking plesiosaurs as juveniles and shows why systematics, paleoecology and evolutionary reconstructions of this long-lived marine radiation need to integrate external osteology, bone microstructure and the quality of the fossil record.

Subject of Research: Evolution of skeletal paedomorphism across the plesiosaur fossil record

Article Title: Recognising and quantifying the evolution of skeletal paedomorphosis in Plesiosauria

Article References: Araújo, R., & Smith, A. S. (2023). Recognising and quantifying the evolution of skeletal paedomorphosis in Plesiosauria. Fossil Record, 26(1), 85-101. https://doi.org/10.3897/fr.26.97686

Image Credits: AI Generated

DOI: 10.3897/fr.26.97686

Keywords: plesiosaurs, paedomorphism, heterochrony, fossil record, osteology, paleohistology, marine reptiles, Mesozoic evolution, skeletal maturity, Recognising, quantifying, evolution

The paper, titled ‘The first brain at the centre: An enteric reframing of the nervous system,’ was authored by Dr Tim Hibberd, Hayley Rhodes and Professor Nick Spencer of Flinders University. It was published as a commentary, meaning it presents an interpretive argument synthesized from existing evidence rather than the results of a single new experiment. Even so, its implications reach into the heart of evolutionary neuroscience, because it suggests that the energy-hungry business of digestion, not cognition, may have been the original driving force behind the emergence of nervous tissue in early animals.

At the center of the argument is the enteric nervous system, the vast web of neurons embedded in the walls of the gastrointestinal tract. Often described as the body’s ‘second brain,’ this network contains hundreds of millions of neurons in humans, a number that rivals or exceeds the neuronal population of the spinal cord. Crucially, the enteric nervous system can operate without direct input from the brain or spinal cord. It senses the chemical and mechanical conditions of the gut lining, processes that information locally, and coordinates complex patterns of muscle contraction, secretion and blood flow that make digestion possible. Isolated segments of intestine continue to generate coordinated peristaltic activity in laboratory conditions, a striking demonstration of just how autonomous this system is.

Dr Hibberd, from Flinders’ College of Medicine and Public Health, argues that this autonomy is precisely why the enteric nervous system deserves to be reconsidered as the body’s original neural architecture. ‘We are proposing a different way of looking at the nervous system,’ he says. ‘The enteric nervous system in the gut can sense its environment, process information and coordinate complex responses. In many ways, it functions like a brain in its own right.’ By that logic, he and his colleagues contend, it may be more accurate to think of the gut’s neural network not as a second brain but as the first one.

The evolutionary reasoning behind this claim rests on a simple biological imperative. For any organism, the overriding priority is securing energy: capturing nutrients, breaking them down and distributing them to tissues. Early multicellular animals faced this challenge without the benefit of centralized nervous systems. A diffuse network of neurons arranged around the digestive apparatus would have provided an immediate survival advantage, allowing a primitive gut to detect food, respond to it and coordinate the movements needed to move it through the body. Only later, as animals grew larger, more mobile and more behaviorally complex, would centralized brains have become useful, and even then, the Flinders researchers argue, the brain’s fundamental role remained to support the gut’s mission of energy acquisition.

This perspective aligns with features of modern nervous system diversity. Many animals with simple body plans, including certain cnidarians and other basal lineages, possess nerve nets with little or no centralization, organized largely around the oral and digestive regions. In more complex animals, the gut tube retains its own complete nervous system regardless of how elaborate the brain has become. The persistence of this independent enteric circuitry across such a wide range of species, the researchers suggest, hints at its ancient origins. Rather than being a derived or secondary feature, the gut’s nervous system may preserve the architecture of the earliest nervous systems that ever evolved.

Senior author Professor Nick Spencer, from Flinders Health and Medical Research Institute, says the theory helps explain a puzzle that has long interested physiologists: why the gut remains so influential in directing functions throughout the body, long after brains capable of vision, memory and movement appeared. ‘The gut is constantly gathering information and communicating with other organs,’ says Professor Spencer. ‘It plays a major role in regulating digestion, metabolism and other functions essential for survival. These fundamental processes may have helped drive the evolution of the nervous system.’ The gut, in this framing, is not a passive organ awaiting instructions but an active sensing and signaling hub whose outputs ripple through hormones, immune signaling and neural pathways to shape appetite, metabolism and even mood.

The reframing also speaks to a growing body of research on the gut-brain axis, the bidirectional communication network linking the gastrointestinal tract with the central nervous system. The vagus nerve provides a direct neural highway between gut and brain, while gut-derived hormones modulate hunger, satiety and glucose regulation. Clinical observations have reinforced the significance of this axis: alterations in gut function are increasingly documented in conditions as varied as Parkinson’s disease, obesity and diabetes. In Parkinson’s disease, for example, aggregates of the protein alpha-synuclein have been detected in the enteric nervous system, prompting ongoing debate about whether pathological processes may begin in the gut before reaching the brain. A theoretical framework that treats the gut’s nervous system as primary, rather than peripheral, could reshape how such connections are investigated.

The Flinders team is candid that their proposal is unlikely to change medical practice overnight. As an opinion piece, it functions as a challenge to the field, an invitation to reinterpret existing evidence through a different lens rather than a definitive proof of gut-first neural evolution. But the authors argue that the conceptual stakes are high, because the assumptions scientists bring to anatomy shape the questions they ask about disease. ‘The way we think about the body shapes the way we investigate disease,’ says Dr Hibberd. ‘If we begin to view the gut as a central player in nervous system function, it may open up new avenues for research.’ Those avenues could include exploring the enteric nervous system as a therapeutic target for metabolic and neurodegenerative disorders, or re-examining the evolutionary record of early animals with fresh attention to the neural tissue surrounding the digestive tract.

Whatever the ultimate verdict of the scientific community, the paper injects new energy into one of evolution’s oldest questions. If the Flinders researchers are right, the human brain, with all its capacity for language, art and abstraction, is best understood not as the founding organ of the nervous system but as a brilliant late addition, recruited in service of an older, quieter intelligence coiled within the gut. The idea invites scientists and the public alike to reconsider where the story of the nervous system truly began: not in the skull, but in the ancient, energy-driven demands of the gut that every animal, from the simplest worm to the human being, still carries at its core.

Subject of Research: Evolutionary origins of the enteric nervous system and the gut-first hypothesis of brain evolution

Article Title: What evolved first – our brain or gut?

Article References: What evolved first – our brain or gut?. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: enteric nervous system, evolution, gut-brain axis, neuroscience, digestion, Flinders University, Journal of Physiology, brain evolution, Parkinson's disease, metabolism, second brain, physiology

The achievement, published in the journal Fossil Record, matters because cricket wings are notoriously difficult to interpret in fossils. Most ancient insects survive only as flattened imprints in rock, and even the lucky specimens preserved in amber often have incomplete wings or veins whose trajectories are impossible to follow. In Picogryllus carentonensis, the right forewing is damaged, but crickets habitually fold their right wing above the left one, so the left forewing underneath was almost fully complete. The team used propagation phase-contrast X-ray synchrotron microtomography at the European Synchrotron Radiation Facility in Grenoble, scanning the specimen at beamline ID19 with 30 keV X-rays, 2,500 projections over 180 degrees, and a voxel size of just 20.24 micrometres. From those scans, more than 3,600 two-dimensional slices across three spatial planes were assembled into a digital 3D model of the wing.

Why go to such lengths over a wing the size of a grain of rice? Because insect wing venation is one of the most hotly debated subjects in palaeontology. For over two centuries, scientists have argued about how many main veins insect wings contain and how to identify them, and no single system has ever been universally accepted. A recent framework proposes seven main veins in neopteran insects: the costal, subcostal, radial, median, cubital, postcubital and anal veins. Crucially, microtomography gives researchers access to the very base of the wing, where veins emerge from structures called basivenalia, allowing veins to be identified by their origins rather than by superficial appearance. This is what makes a 3D reconstruction so much more powerful than a photograph of an imprint.

The reconstruction revealed that the general structure of the forewing of Picogryllus carentonensis is strikingly similar to that of modern crickets. The wing is divided into a lateral field, running vertically along the body, and a dorsal field, lying flat over the insect’s back, separated by a median fold. The lateral field carries three main veins, Sc, R and M+CuA, with the subcosta pectinate, bearing at least eight oblique branches directed toward the anterior edge. Between the radial and median veins lies the long, narrow lanceolate cell, roughly 4.5 times longer than wide, a hallmark of singing crickets. The dorsal field contains the cubital, postcubital and anal veins, including the harp, a triangular resonating cell, and the mirror, the rounded cell that plays a key role in projecting cricket song.

The researchers identified features that are recognised synapomorphies, shared derived characters, of the Orthoptera: the fusion of the media and cubitus anterior veins, and the fusion of CuA with the first anterior branch of CuPa. The two postcubital veins run near the posterior margin of the wing, forming the so-called chord veins of crickets, and an arculus, a distinctive crossvein structure associated with sound production, is present. The pattern matches almost perfectly the general venation scheme proposed for crickets in 2023, which was built on precise homology criteria rather than guesswork. This validation means the fossil can now be placed on a firm morphological footing alongside its living relatives in the family Oecanthidae.

But the tiny cricket also holds a surprise. Its mirror, the cell central to sound radiation, is crossed by two strong, parallel crossveins, a rare feature in extant crickets. Few living species show more than one crossvein in this cell, although some phalangopsid crickets, such as Paragryllus and Paragryllodes, have up to six concentric crossveins, and winged Phaloriinae typically have two transverse ones. Applying the new venation pattern to the genus Oecanthus shows that what looked like two crossveins in that group is actually a single crossvein plus a highly modified c1 cell, making the two-crossvein mirror of Picogryllus genuinely unusual.

Why would a singing cricket need extra crossveins in its mirror? The researchers propose a functional hypothesis: in many contemporary crickets, the mirror is involved in sound propagation, and the crossveins may reinforce the wing membrane against the stresses of vibration. Large, flexible forewings may need such reinforcement to withstand repeated vibration during calling. There is an intriguing size angle as well. In extant crickets, the frequency of the calling song increases as body size decreases, and the smallest living singing crickets are much larger than Picogryllus. The extra crossveins may have allowed the call of this miniature species to remain in relatively low frequencies despite its tiny sound-producing apparatus, effectively stiffening the vibrating surfaces in a way that shifted its acoustic output.

The fossil’s affinities add another layer to the story. The extinct families Baissogryllidae and Protogryllidae show crossveins in the homologous region, but their cell there is open and not closed by a reinforced s1 crossvein as in true crickets, and they also possess a diagonal crossvein and an ant-mirror cell that Picogryllus lacks. The connections of the crossveins in Picogryllus are identical to those in the living phalangopsid Lerneca fuscipennis, which could support a hypothesis of primary homology, but given that these lineages are not closely related to the Oecanthidae, the crossveins are most probably homoplastic, features that evolved independently in different lineages rather than being inherited from a common ancestor.

Microtomography has its limits at this scale. The stridulatory file, the row of teeth on a wing vein that scrapes against the other wing to produce sound, could not be reconstructed, which prevents any estimate of the frequency of the calling song of Picogryllus. The authors suggest that nanotomography might increase resolution, but caution that the regions in question appear damaged, so finer scanning would probably not recover the missing structures. Even so, this is the first time an almost complete 3D venation pattern has been reconstructed in a fossil Orthoptera, and the technique is proving transformative for studying falsely-flat structures like wings, in both fossil and living taxa.

The implications reach well beyond one tiny cricket. Precise morphological information from fossils is exactly what is needed for modern phylogenetic analyses, including tip dating and total-evidence approaches that combine molecular data from living species with morphological data from extinct ones. Fossils lack DNA, but a validated venation pattern like this one allows accurate placement of extinct species in the tree of life. Two other Cretaceous oecanthid crickets recently described from Myanmar amber, Crassicorpus maculatus and Ordicalcaratus inconditus, are congruent with the new interpretations, though their mirror cells will need closer checking. With this exquisitely preserved 100-million-year-old wing now fully mapped, palaeontologists have a validated morphological basis for reconstructing how cricket wings, and the songs they produce, evolved over hundreds of millions of years.

Subject of Research: Paleontology

Article Title: First 3D reconstruction of a forewing of a fossil Orthoptera : Interpreting the venation pattern in the smallest known cricket with a stridulatory apparatus, † Picogryllus carentonensis ( Orthoptera , Grylloidea , Oecanthidae )

Article References: Ferreira, J., Josse, H., Denadai de Campos, L., Nel, A., & Desutter-Grandcolas, L. (2024). First 3D reconstruction of a forewing of a fossil Orthoptera: Interpreting the venation pattern in the smallest known cricket with a stridulatory apparatus, †Picogryllus carentonensis (Orthoptera, Grylloidea, Oecanthidae). Fossil Record, 27(1), 101-110. https://doi.org/10.3897/fr.27.113100

Image Credits: AI Generated

DOI: 10.3897/fr.27.113100

Keywords: paleontology, crickets, orthoptera, amber fossils, microtomography, evolution, bioacoustics, Cretaceous, First, reconstruction, forewing, fossil

Pygmy grasshoppers, scientifically known as Tetrigidae, are a peculiar family of small orthopterans found across the globe, often lurking near water or scuttling through leaf litter. In the vast majority of the roughly 2,000 known species, the forewings have been reduced to tiny flaps called tegmenula, while the hind wings remain fully developed and functional for flight. This combination, miniature forewings paired with full-sized hind wings, is one of the family’s defining traits. The new fossil upends that picture. With tegmenula reaching the midpoint of its hind femur, Rusmithia gorochovi holds the record for the longest forewings ever documented in a true pygmy grasshopper, living or extinct.

The story of the specimen’s journey to science is nearly as remarkable as the insect itself. The single adult female holotype was purchased on eBay by Dr. Ru Smith, an amateur naturalist and collector based in York, United Kingdom. Recognizing that the creature trapped in the golden resin was something unusual, Smith contacted the researchers and ultimately made the specimen available for formal study. In gratitude, the team named the new genus after him, while the species epithet honors Dr. Andrei V. Gorochov, a world-renowned expert on fossil Orthoptera. The holotype is now deposited in Smith’s private collection, and it was Smith who photographed and drew the delicate details preserved within the amber.

Dating Baltic amber is a notoriously tricky business. The deposits can range anywhere from 25 to 43 million years old, though most material is assigned to the Priabonian stage of the late Eocene, roughly 38 to 34 million years ago. The authors place their fossil in the Middle Eocene, following the commonly cited Lutetian to Priabonian estimates. The holotype was recovered from the Anna mine near Yantarny in Russia’s Kaliningrad region, the classic source of the world’s finest amber fossils. Encapsulated alongside the grasshopper was a small fly belonging to the family Sciaridae, identified by Andrew Ross of the Natural History Museum in London, a detail that would later prove informative about the ancient habitat.

Classifying the fossil required careful attention to anatomical details that separate the subfamilies of Tetrigidae. Batrachideinae, the subfamily to which the new genus belongs, is characterized by antennae with more than 19 segments, rectangular side lobes on the pronotum known as paranota, and mid-femora with a grooved dorsal margin. Rusmithia gorochovi ticks all these boxes, with an antenna of at least 20 segments and a smooth, flat pronotum whose anterior margin forms an obtuse triangle rather than a spine. The insect’s body measures 18 millimeters, its pronotum 17 millimeters, and its hind femur 9 millimeters, while the tegmenula stretch an extraordinary 6 millimeters. The researchers assigned it, together with the previously described Baltic amber genus Danatettix, to a newly erected tribe, Rusmithini, representing what they call the European Batrachideinae.

The significance of those long forewings lies in what they suggest about the deep evolutionary history of the family. Among the oldest putative pygmy grasshoppers, the Cretaceous genera Archaeotetrix and Prototetrix from Transbaikalia, also show elongated forewings, which is why scientists have long believed that the ancestral pygmy grasshopper possessed larger forewings that were gradually reduced over time. But the picture is muddled. The venation of those Cretaceous fossils differs from that of Rusmithia, and their placement within the family remains uncertain, with some researchers questioning whether they are true tetrigids at all rather than specialized relatives of an extinct locust-like group.

The authors weigh several competing explanations for the new fossil’s anatomy. One possibility is that the visible radius and costa veins in the tegmina represent an ancestral condition, a pattern also seen in Tridactyloidea, the pygmy mole crickets, which modern phylogenetic analyses place at the base of the Caelifera, the group that includes grasshoppers and their relatives. However, wing reduction is known to occur repeatedly across many insect lineages, and as wings shrink, their venation typically simplifies until only the structurally essential veins remain. This means convergence cannot be ruled out on the available evidence. Complicating matters further, two other fossil batrachideines, the European Danatettix hoffeinsorum and the American Eotetrix unicornis from Wyoming’s Green River Formation, both possess typical, reduced tetrigid forewings, casting doubt on any simple story of continuous forewing shrinkage through time.

The most parsimonious interpretation, the researchers conclude, is that Rusmithia belongs to a lineage of Batrachideinae in which longer forewings were retained, possibly representing an intermediate stage between the fully winged ancestral form and the reduced condition seen in modern species. If that reading is correct, it implies that forewing reduction evolved at least twice within Tetrigoidea, the superfamily that contains the pygmy grasshoppers. Two enigmatic Baltic amber species, Acrydium bachofeni, described in 1937 with tegmenula reported at 5 millimeters long, and Succinotettix chopardi, with antennae of at least 19 segments, might also belong to this tribe or its close relatives, but the authors declined to transfer them because their type specimens could not be examined and their whereabouts remain unclear. Locating those types, they argue, would go a long way toward untangling the taxonomy of European fossil batrachideines.

Beyond its evolutionary implications, the fossil offers a vivid window into the world of Eocene Europe. Baltic amber is widely regarded as a gold mine for fossil arthropods, preserving an astonishing diversity of insects in exquisite three-dimensional detail. Recent botanical work on plant inclusions has reconstructed the ancient Baltic landscape as a mosaic of habitats, from coastal swamps to mixed conifer and angiosperm forests, resembling the warm-temperate woodlands found today in East Asia and North America. Such environments harbor numerous modern pygmy grasshoppers, including batrachideines. The authors therefore suggest, with reasonable confidence, that Rusmithia gorochovi lived in warm, humid habitats, feeding on algae, mosses, and detritus. The sciarid fly trapped beside it reinforces this picture, since these flies also thrive on detritus and fungi, indicating that the two insects shared the same microhabitat before both met their fate in dripping resin.

The fossil record of Tetrigidae remains tantalizingly sparse, with all known extinct species fitting comfortably into a single table, from Cretaceous Transbaikalia to Miocene Dominican amber, where famous inclusions such as Electrotettix attenboroughi, named for Sir David Attenborough, have emerged in recent years. Each new specimen, the authors stress, adds a crucial brushstroke to a tragically incomplete portrait of the family’s evolution. Rusmithia gorochovi, with its record-breaking forewings and its ambiguous position between ancestral and modern body plans, may prove to be one of the most important brushstrokes yet. Whether its long tegmenula are a surviving ancestral trait or an independent reinvention, the tiny grasshopper sealed in amber is already reshaping what scientists thought they knew about how wings shrink, disappear, and occasionally refuse to.

Subject of Research: Evolution of reduced forewings in pygmy grasshoppers revealed by a new Eocene Baltic amber fossil

Article Title: A new long-winged pygmy grasshopper in Eocene Baltic amber raises questions about the evolution of reduced tegmenula in Tetrigidae ( Orthoptera )

Article References: Skejo, J., Kasalo, N., Thomas, M. J., & Heads, S. W. (2024). A new long-winged pygmy grasshopper in Eocene Baltic amber raises questions about the evolution of reduced tegmenula in Tetrigidae (Orthoptera). Journal of Orthoptera Research, 33(1), 21-26. https://doi.org/10.3897/jor.33.105144

Image Credits: AI Generated

DOI: 10.3897/jor.33.105144

Keywords: pygmy grasshoppers, Tetrigidae, Baltic amber, Eocene, fossil insects, forewing reduction, Batrachideinae, orthoptera, paleontology, evolution, new species, tegmenula