To save content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about saving content to .
To save content items to your Kindle, first ensure no-reply@cambridge.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Aquatic ecosystem monitoring is important for supporting biodiversity and environmental stability, yet it faces increasing threats from pollution, climate change and human activities. This study presents the development and deployment of a low-cost multi-sensor data logging system for real-time monitoring of Lagos Lagoon. The system integrates temperature sensors, hydrophones, and imaging devices to collect environmental data. Results showed that temperature variations ranged from ~28.5 to 31.5 °C, with fluctuations influenced by partial and full submersion. Acoustic analysis revealed dominant frequencies below 500 Hz, indicative of biological and anthropogenic activity in the lagoon. Machine learning models trained on 31 species closely agreed with the environmental dataset despite some noticeable deviations, suggesting potential improvements through data augmentation and model refinement. Despite challenges such as signal attenuation in submerged conditions and image degradation due to water turbidity, the system successfully recorded and logged environmental parameters. This study demonstrates the feasibility of using artificial intelligence-powered, cost-effective sensor technology for continuous aquatic monitoring, with implications for biodiversity conservation and water resource management. Future research should focus on enhancing wireless communication, refining species detection algorithms and improving sensor resilience in harsh aquatic conditions.
Turbulence closures are essential for predictive fluid flow simulations in both natural and engineering systems. While machine learning offers promising avenues, existing data-driven turbulence models often fail to generalise beyond their training datasets. This study identifies the root cause of this limitation as the conflation of generalisable flow physics and dataset-specific behaviours. We address this challenge using symbolic regression, which yields interpretable, white-box expressions. By decomposing the learned corrections into inner-layer, outer-layer and pressure-gradient components, we isolate universal physics from flow-specific features. The model is trained progressively using high-fidelity datasets for plane channel flows, zero-pressure-gradient turbulent boundary layers (ZPGTBLs), and adverse pressure-gradient turbulent boundary layers (PGTBLs). For example, direct application of a model trained on channel flow data to ZPGTBLs results in incorrect skin friction predictions. However, when only the generalisable inner-layer component is retained and combined with an outer-layer correction specific to ZPGTBLs, predictions improve significantly. Similarly, a pressure-gradient correction derived from PGTBL data enables accurate modelling of aerofoil flows with both favourable and adverse pressure gradients. The resulting symbolic corrections are compact, interpretable, and generalise across configurations – including unseen geometries such as aerofoils and Reynolds numbers outside the training set. The models outperform baseline Reynolds-averaged Navier–Stokes closures (e.g. the Spalart–Allmaras and shear stress transport models) in both a priori and a posteriori tests. These results demonstrate that explicit identification and retention of generalisable components is key to overcoming the generalisation challenge in machine-learned turbulence closures.
A new species of flatfish (Pleuronectiformes) is described from early Oligocene deposits of the Keasey Formation near Mist, Oregon, USA. The rare preservation of an articulated fish in the Mist crinoid lagerstätte is likely because the specimen represents a relatively pelagic immature individual that had not yet settled into the typical benthic lifestyle of adult flatfishes. The new species is included in a phylogenetic analysis; although it is lacking many characters, it is recovered as an early diverging lineage, sister to the extant members of the superfamily Pleuronectoidea. This phylogenetic position fits well with the age of this fossil and conforms with the origin of flatfishes occurring in the early Cenozoic, followed by diversification and radiation throughout the Eocene, Oligocene and Miocene epochs.
Compressible jets impinging on a perpendicular surface can produce high-intensity, discrete-frequency tones. The character of these tones is a function of nozzle shape, jet Mach number, impingement-plate geometry, and the distance between nozzle and plate. Though it has long been recognised that these tones are associated with a resonance cycle, the exact mechanism by which they are generated has remained a topic of some debate. In this work, we present evidence for a number of distinct tone-generation mechanisms, reconciling some of the different findings of prior authors. We demonstrate that the upstream-propagating waves that close resonance can be confined within the jet, or external to it. These waves can be either weak and relatively linear, or strong and nonlinear from their inception. The waves can undergo coalescence or merging, and in some configurations, pairs of waves rather than singletons appear. We discuss both historical and new evidence for multiple distinct processes by which upstream-propagating waves are produced: direct vortex sound, shock leakage, wall-jet-boundary fluctuations, and wall-jet shocklets. We link these various mechanisms to the disparate collection of upstream-propagating waves observed in the data. We also demonstrate that multiple mechanisms can be provoked by a single vortex, providing an explanation as to why sometimes pairs of waves or merging waves are observed. Through this body of work, we demonstrate that rather than being in opposition, the various pieces of past research on this topic were simply identifying different mechanisms that can support resonance.
The paper by Pružina et al. (2025) J. Fluid Mech. 1009, sheds new light on the physical processes responsible for the formation of distinct layers in double-diffusive convection. Towards this end, it discusses direct numerical simulation results within the framework of sorted buoyancy coordinates. In particular, it demonstrates that the eddy diffusivity is negative everywhere, including in the interior of the well-mixed layers. This approach holds promise for analysing other, closely related, flow configurations that give rise to the emergence of pronounced layering features.
Dot array deposition through electrohydrodynamic (EHD) printing is widely used for high resolution and material utilization advantages. However, the conventional printing method is subject to a printing frequency limit known as the capillary frequency of the meniscus oscillation, where the jet directly contacts the substrate. This makes the printing frequency of EHD printing maintain at a low level and that is difficult to improve. In this work, a method for high-frequency EHD printing through continuous pinch-off is proposed. The characteristic frequency is broken through. A model is established to reveal the printing mechanism by combining the Poisson–Nernst–Planck equation and the phase field method. The unreal charge leakage is prevented by constructing a transition function for the fluid’s properties. The stability of the Taylor cone’s deformation and the droplets’ generation is studied. The measurement criterion for printing frequency is determined. The suitable printing height that can prevent the jet from directly contacting the substrate is obtained by investigating its influence on the printing states and frequency. The phase diagram considering the liquid’s conductivity and viscosity is presented to distinguish whether the printing is based on the end-pinching or Rayleigh–Plateau instability. The influence of the conductivity, viscosity, flow rate and printing voltage on the printing frequencies is studied quantitatively. Finally, scaling laws for printing frequency are proposed by theoretical analyses and summarizing the numerical data. This work could be beneficial for further enhancing the printing frequency of EHD printing.
Spaceflight missions must limit biological contamination on both the outbound and return legs to comply with planetary protection requirements. Depending on the mission profile, contamination concerns may include the potential presence of bioactive molecules as defined by NASA’s Planetary Protection policies. Thus, the present study has examined the temperature and time requirements for sufficient inactivation/degradation of an infectious, heat-stable prion protein (Sup35NM), which serves as a model bioactive molecule. Bovine serum albumin was used to establish the method parameters and feasibility. Differential scanning calorimetry, Fourier transform infrared spectroscopy, analytical reversed-phase high-performance liquid chromatography, and mass spectrometry were utilized to analyze heat-treated samples, with non-treated samples serving as controls. Heat treatment at 400°C for 5 seconds was found to result in substantial decomposition of Sup35NM. In addition to the disruption of the protein backbone amide bonds, the side chain residues were also compromised. Fragments of molecular weight <4600 were observed by mass spectrometry but the impact of treatment on both the backbone and side chains of Sup35NM suggested that these fragments would not self-associate to create potentially pathogenic entities. The present methodology provided insight into the protein degradation process and can be applied to a variety of treatment strategies (e.g., any form of sterilization or inactivation) to ensure a lack of protein-based contamination of isolated extraterrestrial specimens.
Biodiversity knowledge gaps and biases persist across low-income tropical regions. Genetic data are essential for addressing these issues, supporting biodiversity research and conservation planning. To assess progress in wildlife genetic sampling within the Philippines, I evaluated the scope, representativeness, and growth of publicly available genetic data and research on endemic vertebrates from the 1990s through 2024. Results showed that 82.3% of the Philippines’ 769 endemic vertebrates have genetic data, although major disparities remain. Reptiles had the least complete coverage but exhibited the highest growth, with birds, mammals, and amphibians following in that order. Species confined to smaller biogeographic subregions, with narrow geographic ranges, or classified as threatened or lacking threat assessments were disproportionately underrepresented. Research output on reptiles increased markedly, while amphibian research lagged behind. Although the number of non-unique authors in wildlife genetics studies involving Philippine specimens has grown steeply, Filipino involvement remains low. These results highlight the uneven and non-random distribution of wildlife genetic knowledge within this global biodiversity hotspot. Moreover, the limited participation of Global South researchers underscores broader inequities in wildlife genomics. Closing these gaps and addressing biases creates a more equitable and representative genetic knowledge base and supports its integration into national conservation efforts aligned with global biodiversity commitments.
Sulfur stable isotope ratios (δ34S) have become increasingly common in archaeology for studying paleodiet, especially in occasions where there is a need to identify aquatic resource consumption more accurately. This is particularly relevant in the Baltic Sea region, where brackish conditions tend to mask “typical” marine carbon isotopic signals. Here we report new δ34S values for 126 human bone collagen samples which will be analyzed together with previously published data to investigate the potential of sulfur isotopes as an alternative proxy for aquatic resource consumption in historic period Estonia (ca. AD 1100‒1800). Bayesian statistical programming was used to provide quantitative dietary estimates, suggesting that the diet of the general population was predominantly terrestrial. The inclusion of δ34S as an additional dietary proxy produced generally comparable model results to the scenario that excluded δ34S. A sub-selection of samples was also radiocarbon dated and calibrated to take into account potential reservoir effects. For burials of commoners, the average contribution of 10% fish to dietary carbon does not significantly alter calibrated date ranges, even in the occasion where data on local reservoir effects is insufficient. This study has demonstrated both the potential and the pitfalls of using δ34S in this temporo-spatial context, and the new stable isotope and 14C data have shed light onto individual site-histories but also to broader cultural processes and changes that occurred during these turbulent times in this region.
Breaking wave impacts on rigid structures have been extensively studied, yet the role of structural elasticity in shaping the impact and response remains insufficiently understood. In this study, we experimentally investigate the hydroelastic behaviour of a vertical cantilever plate subjected to multimodal solitary breaking wave impacts. The plate is mounted near the still water level on a 1 : 10 sloping beach, and the wave height-to-depth ratio ($H/h$) is varied from 0.15 to 0.40 to systematically control the impact type from non-breaking to highly aerated wave impacts. We show that aeration significantly affects hydroelastic impacts. The spatio-temporal extent of the impact pressure on the elastic plate increases with air entrapment, while the peak pressure becomes highly sensitive as the wave approaches the flip-through regime. Pressure oscillations associated with bubble formation induce high-frequency structural vibrations, particularly under low-aeration conditions. Furthermore, we find that the elasticity has a limited effect on the peak pressure, impact duration and impulse, but increases the maximum quasi-hydrostatic force on the plate for the scenarios investigated. Following the impact, two distinct free-top deflections are identified, i.e. a deflection $\Delta x_{\textit{imp}}$ with high acceleration induced by the impact pressure and a deflection $\Delta x_{{hp}}$ with high magnitude caused by the maximum quasi-hydrostatic pressure. These deflections scale with the Cauchy number as $\Delta x_{\textit{imp}}/l \sim Ca_{\textit{imp}}/6$ and $\Delta x_{{hp}}/l \sim Ca_{{hp}}/12$ (where l is the plate length), exhibiting parabolic and linear trends with $H/h$, respectively. This work presents a benchmark dataset and introduces a predictive law for structural deflection, providing practical insights into hydroelastic effects across various impact regimes.
Astrobiology is a scientific field that is very interdisciplinary and developing very fast, with many new discoveries generating a high level of attention in both the scientific community and the public. A central goal of astrobiology is to discover life beyond Earth which is, with our current instrumentation and knowledge, arguably within our reach. However, knowledge exchange crossing disciplinary boundaries is becoming increasingly challenging due to different usage of nomenclature and scientific controversies often limited to subdisciplines. There have been some efforts to compile organized databases of terms, concepts and other relevant material within some of the subfields contributing to astrobiology, for example through manually curated online portals designed to benefit students, teachers and practitioners of astrobiology-related research. However, the developments within the subfields and the potentially premature communication of research findings are too fast for objective research portals to remain reliable and up-to-date enough to enable well-informed scientific discussions. We suggest here a novel strategy for developing an online tracers portal as a self-maintaining and self-updating information platform, that would allow not only for a relatively unbiased selection of research results, but also provide fast access to latest scientific discoveries together with potential controversies, such that users of the tracers portal can form their own opinion on all available data rather than obtaining an already filtered and potentially biased selection of information.
The Brazil nut tree Bertholletia excelsa is an icon of Amazon conservation through sustainable use. Moderate disturbance, such as that caused by swidden agriculture, favours this heliophilic species. Our systematic literature review of Bertholletia studies and historical records addresses the following questions: do slash-and-burn farming systems increase Bertholletia density and growth? What do historical records reveal about the links between Bertholletia life history and human occupation? And what policies and regulations shape the current context for harnessing this synergistic potential for sustainable use? Compared to mature forests, slash-and-burn fallow seedling/sapling densities (11–82 individuals ha–1, with a mean of 29 individuals ha–1) are greater and faster-growing. Extant Bertholletia trees that were cut and burned during swidden preparation resprout as forked individuals and supplement new seeds buried by Dasyprocta spp. The presence of large forked Bertholletia trees and the occurrence of anthropogenic soils, particularly brown soils associated with Brazil nut tree groves, provide evidence that extant Bertholletia groves may be islands of active and passive agroecological management by ancestral Indigenous populations and local communities. This supports the notion that conservation through sustainable use can maintain Amazonian megadiversity. Furthermore, fire has been used in the Amazon since the onset of crop cultivation (including Bertholletia) c. 4500 years ago, suggesting that a more effective approach than banning fires would be to implement a systematic and methodical fire and fuel management strategy, given the ineffectiveness of command-and-control policies in this regard. The 124 conservation units and Indigenous lands in the Amazon containing Brazil nut trees reinforce the importance of policies to create protected areas. Evidence suggests that the presence of an Amazonian biocultural forest – a phenomenon resulting from the interaction between human activities and natural processes – can be sustainably used to promote what might be termed ‘sociobiodiversity conservation’.
The effect of Stokes number on turbulence modulation in particle-laden channel flow is investigated through four-way coupled point-particle direct numerical simulations, with the mass loading fixed at 0.6 and the friction Stokes number $St^+$ varying from 3 to 300. A full transition pathway is observed, from a drag-enhanced to a drag-reduced regime, eventually approaching the single-phase state as $St^+$ increases towards 300. A set of transport equations for the particle phase is derived analytically to characterise the interphase coupling, within the framework of the point-based statistical description of particle-laden turbulence. By virtue of this, two dominant mechanisms are identified and quantitatively characterised: a positive, particle-induced extra transport that decreases monotonically with increasing $St^+$, and a negative, particle-induced extra dissipation that varies non-monotonically with $St^+$. The coupling of these two mechanisms leads to a direct contribution of the particle phase to the shear stress balance, the turbulent kinetic energy budgets and the Reynolds stress budgets. Consequently, as $St^+$ increases, the self-sustaining cycle of near-wall turbulence transitions from being augmented to being suppressed and, eventually, returns to the single-phase state. This gives rise to an indirect effect, manifested as a non-monotonic modulation of Reynolds shear stress and turbulence production rate. Taken together, complex interplays between particle-modified turbulent transport, particle-induced extra transport and extra dissipation are analysed and summarised, providing a holistic physical picture composed of consistent interpretations of turbulence modulation induced by small heavy particles.
The Central Indian Tectonic Zone (CITZ) formed during the Mesoproterozoic north-south collision between the Bundelkhand and Bastar Cratons. The origin of the deformation of the Late-Paleoproterozoic Lower Vindhyan Group (LVG), which occurs in the sedimentary basin adjacent to and north of the CITZ, is debated, with previous researchers supporting synsedimentary processes. To investigate the possibility of a collisional origin, we collected and analysed litho-structural data from the LVG and the Mid-Paleoproterozoic Mahakoshal Supracrustal belt (MSB), which lies within the CITZ. We report, for the first time, diverse structures from the LVG, such as various types of buckle folds including kink-folds, reverse faults and, most importantly, 5–20 meters long outcrops of pop-up structures, which are commonly encountered in fold-thrust belts. However, the adjacent MSB showes relatively complex polyphase deformation with three major deformation stages that produced: (i) E-W-trending regional foliation and diversely oriented folds (D1), (ii) E-W oriented steep folds associated with a large-scale shear zone along the Son-Narmada South Fault (D2) and (iii) local cross-folds (D3). Based on our field observations in the LVG and the MSB, we additionally propose and substantiate, through geological cross-sections and a kinematic model, that the LVG deformed between the D3 and the deposition of the Upper Vindhyan Group. Unlike previous studies, which attributed the deformation structures of the LVG to seismic or soft-sediment processes, our findings confirm that the Mesoproterozoic collision along the CITZ deformed the LVG as the deformation front, aided by detachment folding, propagated into it.
Fossil crinoids from the Ordovician–Silurian boundary interval (~ 443.8 million years) are known from relatively few locations worldwide due to a near-global unconformity that formed from eustatic sea-level fall. This rock record bias has severely hindered study of the timing, magnitude, biogeographic signature, and extinction mechanisms of the Late Ordovician mass extinction (LOME). Crinoids underwent a significant faunal transition between the Late Ordovician and early Silurian that resulted in major shifts between dominant clades, but the driving mechanisms and precise timing of this transition remain unclear. Anticosti Island (Québec, Canada) preserves one of the few Late Ordovician–early Silurian successions of highly fossiliferous, shallow-water rocks that includes the Ordovician–Silurian boundary, making fossils from this region instrumental for better understanding the LOME and Ordovician–Silurian crinoid faunal turnover.
Here we report on a new flexible crinoid, Anticosticrinus natiscotecensis n. gen. n. sp., from the Ordovician–Silurian boundary of Anticosti Island. Phylogenetic analysis of Middle Ordovician–early Silurian flexibles recovers Anticosticrinus natiscotecensis n. gen. n. sp. as a member of family Anisocrinidae. We quantified stratigraphic age uncertainty of A. natiscotecensis using a Bayesian approach for estimating tip-occurrence times in a phylogenetic context. Although results do not provide unequivocal support for the specimen’s precise stratigraphic age, the maximum a posteriori estimate indicates a late Hirnantian age. Regardless of its true age, recognition of Anticosticrinus natiscotecensis provides additional data for evaluating the timing of extinction in flexible crinoids, their diversification and increasing dominance during the Silurian, and crinoid faunal turnover between the Ordovician and Silurian.
Flapping-based propulsive systems rely on fluid–structure interactions to produce thrust. At intermediate and high Reynolds numbers, vortex formation and organisation in the wake of such systems are crucial for the generation of a propulsive force. In this work, we experimentally investigate the wake produced by a tethered robotic fish immersed in a water tunnel. By systematically varying the amplitude and frequency of the fish tail as well as the free stream speed, we are able to observe and characterise different vortex streets as a function of the Strouhal number. The produced wakes are three-dimensional and exhibit a classical V-shape, mainly with two oblique trains of vortex rings convecting outward. Using two-dimensional particle image velocimetry in the mid-span plane behind the fish and through extensive data processing of the velocity and vorticity fields, we demonstrate the strong couplings at place between vortex dynamics, thrust production and wake structure. The main results are twofold. First, by accounting for the obliqueness of the vortex trains, we quantify in experiments the evolution of vortex velocity components in both streamwise and transverse directions. We also measure key geometrical and dynamical properties such as wake angle, vortex ring orientation, diameter and vorticity. Remarkably, all of these quantities collapse onto master curves that also encompass data from previous studies. Second, we develop a quasi-two-dimensional model that incorporates both components of the momentum balance equation and introduces an effective spanwise thickness of the wake structure. This additional dimension, which scales with the physical thickness of the fish, captures the fine features of the three-dimensional wake. The model successfully explains the experimental master curves and highlights the links between vortex dynamics, thrust and wake geometry. Together, this framework offers a comprehensive understanding of the influence of the Strouhal number, providing universal insights relevant for both biological locomotion and bio-inspired propulsion systems.
Depth-averaged systems of equations describing the motion of fluid–sediment mixtures have been widely adopted by scientists in pursuit of models that can predict the paths of dangerous overland flows of debris. As models have become increasingly sophisticated, many have been developed from a multi-phase perspective in which separate, but mutually coupled sets of equations govern the evolution of different components of the mixture. However, this creates the opportunity for the existence of pathological instabilities stemming from resonant interactions between the phases. With reference to the most popular approaches, analyses of two- and three-phase models are performed, which demonstrate that they are more often than not ill posed as initial-value problems over physically relevant parameter regimes – an issue which renders them unsuitable for scientific applications. Additionally, a general framework for detecting ill posedness in models with any number of phases is developed. This is used to show that small diffusive terms in the equations for momentum transport, which are sometimes neglected, can reliably eliminate this issue. Conditions are derived for the regularisation of models in this way, but they are typically not met by multi-phase models that feature diffusive terms.
We present a deep learning architecture that reconstructs a source of data at given spatio-temporal coordinates using other sources. The model can be applied to multiple sources in a broad sense: the number of sources may vary between samples, the sources can differ in dimensionality and sizes, and cover distinct geographical areas at irregular time intervals. The network takes as input a set of sources that each include values (e.g., the pixels for two-dimensional sources), spatio-temporal coordinates, and source characteristics. The model is based on the Vision Transformer, but separately embeds the values and coordinates and uses the embedded coordinates as relative positional embedding in the computation of the attention. To limit the cost of computing the attention between many sources, we employ a multi-source factorized attention mechanism, introducing an anchor-points-based cross-source attention block. We name the architecture MoTiF (multi-source transformer via factorized attention). We present a self-supervised setting to train the network, in which one source chosen randomly is masked and the model is tasked to reconstruct it from the other sources. We test this self-supervised task on tropical cyclone (TC) remote-sensing images, ERA5 states, and best-track data. We show that the model is able to perform TC ERA5 fields and wind intensity forecasting from multiple sources, and that using more sources leads to an improvement in forecasting accuracy.
Eddies within the meso/submeso-scale range are prevalent throughout the Arctic Ocean, playing a pivotal role in regulating the freshwater budget, heat transfer and sea ice transport. While observations have suggested a strong connection between the dynamics of sea ice and the underlying turbulent flows, quantifying this relationship remains an ambitious task due to the challenges of acquiring concurrent sea ice and ocean measurements. Recently, an innovative study using a unique algorithm to track sea ice floes showed that ice floes can be used as vorticity-meters of the ocean. Here, we present a numerical and analytical evaluation of this result by estimating the kinematic link between free-drifting ice floes and underlying ocean eddies using idealised vortex models. These analyses are expanded to explore local eddies in quasi-geostrophic turbulence, providing a more realistic representation of eddies in the Arctic Ocean. We find that in both flow fields, the relationship between floe rotation rates and ocean vorticity depends on the relative size of the ice floe to the eddy. As the floe size approaches and exceeds the eddy size, the floe rotation rates depart from half of the ocean vorticity. Finally, the effects of ice floe thickness, atmospheric winds and floe collisions on floe rotations are investigated. The derived relations and floe statistics set the foundation for leveraging remote sensing observations of floe motions to characterise eddy vorticity at small to moderate scales. This innovative approach opens new possibilities for quantifying Arctic Ocean eddy characteristics, providing valuable inputs for more accurate climate projections.
Eocene snakes of India have the potential to shed light on the nature of snake diversification on the subcontinent following the Deccan volcanism at the Cretaceous-Paleogene boundary (K-Pg), when India was still a northward-drifting isolated landmass prior to its collision with Asia. Here, we report a diverse snake fauna from the Eocene of Kutch, western India. The fauna, dominated by aquatic forms, includes palaeophiids, a giant madtsoiid, and a possible nigerophiid. The palaeophiids from the middle Eocene (late Lutetian) comprise ?Palaeophis Owen, 1841 and Pterosphenus rannensis n. sp. Together, these taxa enrich the record of fossil snakes in the poorly known late Lutetian of India and represent the youngest record of Palaeophiidae from the Indian subcontinent. Pterosphenus rannensis n. sp. shows intermediate morphology between Palaeophis and Pterosphenus-grade snakes and is phylogenetically the earliest-diverging member of Pterosphenus Lucas, 1898. Additionally, the middle Eocene Pterosphenus biswasi Rage et al., 2003 is reassessed and retained as a valid taxon based on pterapophyseal morphology and overall form. Biogeographic considerations highlight the importance of the Indian fossil record in understanding the origin and diversification of the genus Pterosphenus. The prevalence of niche partitioning is suggested for the palaeophiids, with Pterosphenus rannensis n. sp. recovered from a tidal setting and ?Palaeophis sp. indet. from a marsh/swamp setting. The new Indian madtsoiid from the middle Eocene (early Lutetian) represents a sympatric taxon with the terrestrial/semiaquatic giant Vasuki indicus Datta and Bajpai, 2024 coexisting in a back-swamp marsh setting. The early Eocene (Ypresian) nigerophiid is among the oldest Cenozoic occurrences of this family globally.