Recent discoveries of many new marine reptiles from the Triassic of South China played an important role in understanding the shallow marine ecosystem recovery after the Permo-Triassic mass extinction. Here we report a new large nothosaurian marine reptile, Nothosaurus fortihumeralis sp. nov., represented by three specimens from the Upper Member of the Guanling Formation (middle Anisian, Middle Triassic) of Luxi, South China. Bone histology indicates that the largest individual was adult and close to skeletal maturation. Nothosaurus fortihumeralis is recognized through a combination of apomorphies including: massive humerus with a robust proximal region; distinctly constricted humeral mid-shaft that is half the width of the distal end; distinctly elongated scapular dorsal process tapering to a relatively sharp tip; iliac blade reduced but projecting slightly beyond the posterior margin of the acetabulum. The phylogenetic analysis recovered a monophyletic Nothosaurus with N. fortihumeralis as the sister taxon to Nothosaurus jagisteus. The monophyly of Eusauropterygia is collapsed, with Pachypleurosauria and Nothosauroidea forming a monophyletic Nothosauriformes. Hanosaurus and Majiashanosaurus comprise the consecutive sister groups of Nothosauriformes; together they form a monophyletic Nothosauromorpha. The discovery of N. fortihumeralis adds to the existing evidence of highly diversified large predators in the shallow seas of the eastern Tethys during the Anisian.

Thalattosaurs were a group of large predators in the Triassic oceans, and their diversity is therefore crucial for understanding the biotic recovery from the end-Permian mass extinction in marine environments. Specimen HFUT GL-17-006, a very small thalattosaur skeleton from the Late Triassic Guanling Biota, was recently suggested to represent a new thalattosauroid species sharing no affinity with Xinpusaurus , one of the most common marine reptiles in that biota. Here, we re-examined the morphology of HFUT GL-17-006 and conducted new bone histological analyses. The results indicate that the specimen is a rapidly growing juvenile individual, as evidenced by its small body size, unfused neural arches and centra, and immature bone tissue. Reassessment of the ontogenetically and taphonomically sensitive characteristics of HFUT GL-17-006 recovered it within a clade containing Xinpusaurus suni in our new phylogenetic analysis. Specifically, HFUT GL-17-006 shares with X. suni the absence of a frontal-supratemporal contact and the presence of a reniform radius, both of which distinguish it from other currently recognized species of Xinpusaurus . Thus, HFUT GL-17-006 is identified as a juvenile individual of X. suni , rather than a new thalattosauroid species as recently proposed. Together, our results highlight the importance of rigorously assessing ontogeny before erecting new species or interpreting phylogenetic relationships.

The reliability of ex-situ methodologies in characterizing pore networks within thermally stimulated low-maturity oil shale remains debated due to potential cooling-induced artifacts. This work integrates in-situ scanning electron microscopy (SEM) with high-precision thermal control to systematically evaluate pore evolution during heating (25 °C→500 °C) and subsequent cooling (500 °C→25 °C). Results reveal that thermal upgrading at 500 °C enhances pore development (11% and 111.5% increase in total pore area for two samples). However, the cooling process further amplifies pore network complexity, inducing matrix shrinkage that generates additional macropores (up to 72% pore count increase), thereby distorting ex-situ measurements. While small pores (< 0.05 μm²) dominate across thermal stages and pore aspect ratios remain stable—supporting ex-situ validity for morphological trends—the cooling artifact systematically overestimates macropore abundance, a critical parameter for flow capacity assessment. These findings challenge conventional ex-situ techniques (e.g., gas adsorption, NMR) in replicating in-situ reservoir conditions during thermal recovery. The work proposes integrating in-situ imaging (e.g., heating-stage SEM) as a standard for high-temperature studies, developing cooling-effect calibration protocols for legacy data, and redesigning porosimetry systems with thermal controls. By resolving discrepancies between laboratory measurements and subsurface realities, this research advances predictive models for shale oil mobility and informs optimization of in-situ conversion technologies, ultimately supporting sustainable exploitation of low-maturity shale oil resources.

Heterogeneous coal measure strata are promising for CO2 geo-sequestration with substantial potential for concurrent gas production. We investigate multiphase fluid (adsorbed/free CH4 and CO2) transport dynamics and enhanced gas production concurrent with geological CO2 sequestration. This study is based on the in-situ geological characteristics of the Longtan Formation of the Songzao Coalfield (Sichuan Basin, China) and a reservoir model of stacked coal seam, shale and sandstone strata is developed to evaluate the enhanced gas recovery characteristics. Evaluation of concurrent CO2 geological sequestration and CH4 co-production reveal the initial natural depressurization-driven gas production from the reservoir before CO2 injection subsequently elevates gas pressures. Coupled Thermal-Hydraulic-Mechanic (THM) simulation reveals three key multiphase transport mechanisms: (1) competitive adsorption-driven CH4 displacement with a 3.2:1 CO2/CH4 molar replacement ratio in the coal matrix; and (2) differential phase migration velocities (V-free_gas > V-adsorbed_gas) resulting in transient saturation inversions. Continuous CO2 injection at 7 MPa sequestered similar to 45.4 t CO2 with 88.61 % adsorbed-phase storage, and CH4 recovery increased to 42.22 % (+10.16 % vs. natural depletion). A Phase-specific analysis revealed that the sequestered CO2 exhibits distributed differently among coal, shale, and sandstone formations, in the proportions of 43.78 %, 55.36 %, and 0.86 %, respectively. Notably, the adsorbed phase dominated the CO2 sequestration by mass, comprising 88.61 % of the total stored volume. This work provides fundamental insights into multiphase transport and control for optimizing CO2-enhanced recovery in heterogeneous coal measure systems.

The greatest mass extinction at the end of the Permian, ca. 252 million years ago, led to a tropical dead zone on land and sea. The speed of recovery of life has been debated, whether fast or slow, and terrestrial ecosystems are much less understood than marine. Here, we show fast reestablishment of riparian ecosystems in low-latitude North China as little as ~2 million years after the end-Permian mass extinction. The initial ichnoassemblages in shallow lacustrine and fluvial facies of late Smithian age are monospecific, devoid of infaunalization, with apparent size reduction. In the following Spathian, relatively complex, multi-level, structured riverain ecosystems had been rebuilt including medium-sized carnivores, plant stems, root traces, increased ichnological complexity, and significantly increased infaunalization. Specifically, burrowing behavior had re-emerged as a key life strategy not only to minimize stressful climatic conditions, but possibly to escape predation.

In situ heating is a promising technique for pyrolyzing organic matter within low-maturity oil shales to enhance hydrocarbon recovery. This work establishes a thermal-hydro-mechanical (THM) coupled model to optimize well configurations for the Upper Cretaceous Qingshankou Formation in Songliao Basin (NE China). Integrating anisotropic thermophysical parameters from core experiments (1110-1130 m depth) and field data, we systematically compare six well patterns (three vertical, three horizontal) under a 3-year heating period, evaluating 20 and 30 m well spacings for dual-well setups. A key finding is the pronounced anisotropy in heat propagation, where horizontal transport along bedding planes is approximately 3.2 times faster than vertical transfer, fundamentally controlling the fluid flow and thermal coverage. Results demonstrate that a well spacing of 30 m maximizes the pyrolysis area for both well types, yielding effective heating areas of 1640 m2 (vertical) and 540 m2 (horizontal). Beyond guiding field operations for hydrocarbon recovery, the thermophysical framework provides critical insights for CO2 geo-sequestration, suggesting that the managed anisotropic heat-fluid flow can enhance injectivity and trapping security in analogous layered basins.

In-situ thermal upgrading aids recovery from low-maturity oil shales where low permeability is the rate-limiting feature. We use machine leaning classified pore and pore network morphological descriptions recovered at elevated temperatures to define the dynamic thermal evolution of permeability. These descriptions define key factors influencing permeability evolution, in particular the development of anisotropy and its implication for recovery. Heating enhances permeability by increasing both the number and total cross-sectional area (SEM) of pores. Fractal dimensions indicate that the pore microstructure is anisotropic in the bedding-parallel and bedding-perpendicular directions and is upgraded by elevated temperature. The permeability anisotropy endures throughout the entire heating process and fluctuates at elevated temperature, quantified by the index called anisotropic coefficient of permeability. A newly proposed “aggregation degree” indexes the relative contribution of minority pores to overall permeability – 50% of the permeability (K) is sourced from <8% pores in the SEM section. Increased temperature elicits increased permeability – thus, the temperature applied at the injection well defines the flow limiting permeability threshold at the production wells and thus controls flow rates from the entire heated reservoir. This work provides fresh insights in defining the thermal permeability response of low-maturity oil shales and guides fluids recovery.

Hupehsuchia is a group of marine reptiles from the uppermost Lower Triassic of South China, known for their segmented neural spines covered by dermal ossicles and polydactyl forelimbs. Although five genera and species are currently known for this group, our understanding of their true diversity is limited. In this study, we report a new hupehsuchian, Lentamanusuchus hubeiensis gen. et sp. nov., based on the combination of unique characters in the trunk region and forelimb. These include widely spaced autopodial elements, an extra distal carpal and metacarpal, and a two-layered dermal armour. Phylogenetic analysis recovered the new species as a sister taxon to Parahupehsuchinae within Hupehsuchidae, supporting the gradual addition of extra carpal and digital elements in hupehsuchians. The widely spaced autopodia of Lentamanusuchus hubeiensis represent previously unknown morphologies in hupehsuchians. The wide spacing of the proximal autopodia, along with hyperphalangy, may help smooth the paddle surface to reduce vortices during wrist and proximal digit flexion and extension while swimming. Alternatively, it could result from reduced ossification of manual elements due to diminished muscular control in the manus.https://zoobank.org/urn:lsid:zoobank.org:pub:32503E51-083A-482D-AEFF-4015621A6870

The timing of the emergence of marine reptiles following the Permian-Triassic mass extinction is crucial for studying the recovery of marine ecosystems in the Triassic. Conodonts, key index fossils in the Triassic, are widely used to date the marine reptiles, especially in the Early Triassic. Triassospathodus anhuinensis is a conodont species originally discovered in the upper Spathian of South China, but lacked a comprehensive description, leading to misidentifications and confusion in previous research. Here, we reevaluated Tr. anhuinensis and summarized its morphological characteristics and spatial and temporal distribution based on a review of the literature. We then critically evaluated the age of the primitive ichthyosaur Thaisaurus chonglakmanii from Thailand based on the updated knowledge of Tr. anhuinensis. We sampled the Khao Thong section where T. chonglakmanii was found for conodont study. Tr. anhuinensis elements were obtained from the bed where T. chonglakmanii was collected and also in the bed five metres above the T. chonglakmanii fossil horizon, suggesting a late Spathian age for T. chonglakmanii. A late Spathian age for T. chonglakmanii questions the hypothesis of Thailand as the place of origin of ichthyosaurs in the late Induan or early Spathain. (c) 2024 Elsevier B.V. and Nanjing Institute of Geology and Palaeontology, CAS. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

Elevated temperatures in shale reservoirs are unavoidable during deep shale gas extraction. Thermal conductivity is an essential determinant influencing numerous heat-related activities. Nonetheless, comprehending the thermal conductivity of shale is difficult due to its varied mineral compositions, intricate microstructural characteristics, and the absence of direct measurement techniques. This study addresses these problems by utilizing Time-Domain Thermoreflectance (TDTR) technology, which offers accurate measurements of the thermal properties of mineral phases (at micrometer scale) in shale, such as clay and quartz. The test findings indicate that the clay matrix demonstrates a thermal conductivity of 1.98 W/(m & sdot;K) parallel to the bedding and 1.65 W/(m & sdot;K) perpendicular to it, whereas quartz displays an isotropic value of 6.94 W/(m & sdot;K) in both directions. A two-step homogenization methodology has been developed that accurately represents the layering distribution of grains and accounts for the anisotropic behavior of the clay matrix, integrating the Mori-Tanaka method within lamina and series-parallel models within lamina. The precision of this homogenization process is confirmed by further macroscopic measurements utilizing the laser flash technique, exhibiting an error margin of 5 %. Additionally, quantitative study evaluates the influence of four variables on the anisotropy of thermal conductivity by ANOVA. The findings indicate that the anisotropy of thermal conductivity is predominantly influenced by the orientation of the clay matrix.

In the Early Triassic Nanzhang-Yuan'an fauna from South China, the occurrence of highly diverse marine reptiles suggests that by the late Spathian, the marine ecosystem already exhibited signs of recovery. However, there is currently no record of macrofossils other than marine reptiles found in this fauna. Here, we report the discovery of predatory fish Saurichthys from this fossil assemblage. The new Saurichthys materials are characterised by the derived saurichthyid character, i.e. highly reduced squamation of the trunk and large median scutes on the caudal peduncle. The adaptive features present in these new Saurichthys materials are crucial in generating thrust during rapid swimming or sudden acceleration, and therefore enhancing prey efficiency and evasion capacity, in consistence with the high predator pressure present in the Nanzhang-Yuan'an fauna. The discovery of Saurichthys in Nanzhang-Yuan'an fauna suggests that the trophic structure of Nanzhang-Yuan'an fauna is more complex than previously assumed.

The endemic Hupehsuchia from the Early Triassic of South China is generally accepted as the sister group of ichthyosauriforms and represents the only ichthyosauromorph that lived mainly in the shallow aquatic environment. Therefore, the detailed morphological study of basal hupehsuchians is important to elucidate the relationships of Ichthyosauromorpha with other reptiles. However, Nanchangosaurus, the most basal hupehsuchian taxon, is represented by only two skeletons, and the morphology of its palate and most of the appendicular skeleton remains unknown, limiting its role in resolving the phylogenetic relationships of Ichthyosauromorpha. Here we report a new hupehsuchian specimen from the Early Triassic of South China, which we have identified as a new morphotype of Nanchangosaurus. The new skeleton shows for the first time the morphology of the palate, zeugopodium and autopodium in Nanchangosaurus. Phylogenetic analyses including new morphological information from this skeleton support the recent recovery of an aquatic clade that includes the three major Triassic marine reptile groups. A clade comprising Helveticosaurus and Sauropterygomorpha forms the sister group to Ichthyosauromorpha, and Thalattosauria occupies the most basal position in this large aquatic clade. Archosauromorpha is recovered as a sister group to this aquatic clade, and together they form part of a monophyletic Archelosauria.

In-situ upgrading by heating is feasible for low-maturity shale oil, where the pore space dynamically evolves. We characterize this response for a heated substrate concurrently imaged by SEM. We systematically follow the evolution of pore quantity, size (length, width and cross-sectional area), orientation, shape (aspect ratio, roundness and solidity) and their anisotropy —interpreted by machine learning. Results indicate that heating generates new pores in both organic matter and inorganic minerals. However, the newly formed pores are smaller than the original pores and thus reduce average lengths and widths of the bedding-parallel pore system. Conversely, the average pore lengths and widths are increased in the bedding-perpendicular direction. Besides, heating increases the cross-sectional area of pores in low-maturity oil shales, where this growth tendency fluctuates at < 300 °C but becomes steady at > 300 °C. In addition, the orientation and shape of the newly-formed heating-induced pores follow the habit of the original pores and follow the initial probability distributions of pore orientation and shape. Herein, limited anisotropy is detected in pore direction and shape, indicating similar modes of evolution both bedding-parallel and bedding-normal. We propose a straightforward but robust model to describe evolution of pore system in low-maturity oil shales during heating.

Ichthyosaurs, an iconic lineage of Mesozoic marine reptiles, were an important component of recovering ecosystems after the Permo-Triassic Mass Extinction event. Mixosauridae, a clade of small, early-diverging ichthyosaurs, were of particular significance for this process, being abundant predators in Middle Triassic shallow seas. Despite the abundance of well-preserved mixosaurid specimens from South China, Mixosaurus panxianensis remains the only comprehensively described species, hindering our understanding of the variability, taxonomy and diversity of mixosaurids from this re-gion. Here, we report a new species of Mixosaurus, Mixosaurus luxiensis, from Luxi County, Yunnan Province, South China. The wider postorbital skull portion differentiates the new species from Mixosaurus cornalianus and Mixosaurus kuhnschnyderi from central Europe. The non-durophagous dentition, composed of tiny piercing mesial teeth and robust but pointed distal teeth, resembles the dentition of M. cornalianus. However, the distal teeth of M. luxiensis sp. nov. are twice the size of the mesial ones, in contrast to M. cornalianus, in which the mesial and distal teeth are approximately equal in size. The forelimb exhibits a unique morphology, including a proportionally narrow radius, the presence of a peripheral notch on the ulna, and a large metacarpal V. A preliminary phylogenetic analysis suggests a close affinity of the new taxon with M. cornalianus from Western Tethys. Our study introduces important, new anatomical information on Mixosaurus from South China, useful for future studies of mixosaurid diversity.

Thermophysical properties determine the thermally upgraded area of low-maturity oil shales, which is of significance for restoring oil recovery but needs more in-depth investigations. We introduced a laser-flash NETZSCH LFA-467 analyzer to measure the dynamic response of thermal diffusivity (D), thermal conductivity (K), and specific heat capacity (c) at an in situ elevated temperature as well as their anisotropy in the orthogonal direction relative to shale bedding. The D and K values decrease with a rising temperature, while c values remain almost unchanged at a high temperature. The total organic carbon (TOC) content significantly affects the D and K values, mainly in the anisotropy coefficient (a newly proposed parameter), but sparingly influences the c values. The anisotropy coefficient of samples with a high TOC content is similar to 2 times greater than that with a low TOC content. The greatest D value decay rate of a high TOC content sample reaches similar to 75%, while that for a low TOC content sample is similar to 43%, found in the bedding-perpendicular samples. Results also suggest that the anisotropy of the thermophysical property derives from the lamellar structure of shale rock; the space (like pore and/or fracture) therein is averse to the heat movement. For the hypothetical vertical well mode or horizontal well mode, the arrangement of reasonable space between wells of heat injection and restoring oil production is of significance under the heating-induced dynamic evolution of thermophysical parameters. Hopefully, this work is helpful in enhancing the knowledge on the heat flow behavior in low-maturity oil shale when thermal upgrading is implemented.

The iconic marine raptorial predators Ichthyosauria and Eosauropterygia co-existed in the same ecosystems throughout most of the Mesozoic Era, facing similar evolutionary pressures and environmental perturbations. Both groups seemingly went through a massive macroevolutionary bottleneck across the Triassic-Jurassic (T/J) transition that greatly reduced their morphological diversity, leaving pelagic lineages as the only survivors. However, analyses of marine reptile disparity across the T/J transition have usually employed coarse morphological and temporal data. We comprehensively compare the evolution of ichthyosaurian and eosauropterygian morphology and body size across the Middle Triassic to Early Jurassic interval and find contrasting macroevolutionary patterns. The ecomorphospace of eosauropterygians predominantly reflects a strong phylogenetic signal, resulting in the clustering of three clades with clearly distinct craniodental phenotypes, suggesting "leaps" toward novel feeding ecologies. Ichthyosaurian diversification lacks a discernible evolutionary trend, as we find evidence for a wide overlap of craniodental morphologies between Triassic and Early Jurassic forms. The temporal evolution of ecomorphological disparity, fin shape and body size of eosauropterygians and ichthyosaurians during the Late Triassic does not support the hypothesis of an abrupt macroevolutionary bottleneck near the T/J transition. Rather, an important turnover event should be sought earlier, during times of rapid sea level falls.

Fossil bone from deep time is not only permineralized but strikingly preserves its histological integrity. Exceptions are rare and have not been systematically studied, especially regarding the effects of late diagenesis and low-grade metamorphism experienced by many fossils from Early Mesozoic and Paleozoic rocks and from orogenic belts. Bone samples of 26 specimens of marine reptiles from two Middle and Late Triassic black shale Lagerstatten (Xingyi Fauna and Guanling Biota) of southwest China were examined from a mineralogical perspective by polarized light microscopy, BSE-SEM imaging including cathodoluminescence, EPMA element mapping, and Raman spectroscopy. In addition, paleotemperature was determined from carbonaceous matter via Raman spectroscopy. Preservation ranged from typical fossil bone fluorapatite (FAp) to heavy alteration with loss of histological structure. The mineral fluorite in the Xingyi samples and a continuous bone apatite phase transformation from FAp to recrystallized apatite (RAp) were observed in fossil bone for the first time. Peak diagenetic temperatures were elevated beyond the oil window to low-grade metamorphism (177-209 degrees C), consistent with previous regional studies of coal rank in Guizhou Province. Our results suggest a correlation between the duration of exposure to high temperature and increased alteration levels of bone apatite crystals. We defined five stages of preservation in the two lagerstatten and propose a model for increasing diagenesis and metamorphic alteration of bone histology. Stage I represents no alteration beyond diagenetic mineral precipitation in bone pores. Stage II shows slight loss of apatite crystallite birefringence and beginning of fluorite precipitation. Stage III encompasses the migration of kerogen from host shale into fossil bone, further loss of bone histological structure, and more fluorite precipitation. Stage IV shows recrystallization of FAp to idiomorphic RAp. Stage V is the complete loss of bone matrix structure and replacement by RAp. We also address the correlation of alteration processes with temperature and the sources of F and Ca that formed the fluorite. This study provides reference results for different stages of bone alteration during real geo-history (as opposed to experimental or archaeological time frames), which is essential for studying bone diagenetic processes resulting from protracted exposure to high temperatures and fluids.

After the devastating Permo-Triassic Mass Extinction, several new groups of large reptilian predators invaded the sea in the early part of the Triassic. Among these predators, sauropterygians, consisting of placodonts, pachypleurosaurs, nothosaurs and pistosaurs (including the iconic plesiosaurs), displayed the greatest diversity at both the generic and species levels, and persisted from the Early Triassic to the Late Cretaceous. Here, we report a new species of Pachypleurosauria, Dianmeisaurus mutaensis sp. nov., from a recently discovered Lagerstätte in the Upper Member of the Anisian Guanling Formation. The only known specimen of the new species was collected from a quarry near Muta village, Luxi County, Yunnan Province, South China. Our new phylogenetic analysis based on a novel data matrix recovered the new taxon as a sister group to Dianmeisaurus gracilis —a small pachypleurosaur from the Middle Triassic Luoping biota. The new phylogenetic analysis also collapsed the monophyly of the traditionally recognized Eusauropterygia. Pistosauroidea, Majiashanosaurus , and Hanosaurus comprise the consecutive sister groups to a new clade including Pachypleurosauria and Nothosauroidea. A monophyletic Pachypleurosauria, within which the clade consisting of Dianmeisaurus and Panzhousaurus occupies the basal-most position, is recovered by this study. The clade consisting of Dawazisaurus and Dianopachysaurus forms the sister group to the remaining pachypleurosaurs included in this study. Since Dianmeisaurus , Panzhousaurus , Dawazisaurus , and Dianopachysaurus are all exclusively known from South China, our study provides further evidence to the hypothesis that pachypleurosaurs had a palaeobiogeographic origin in the eastern Tethys.

Only a few Swiss fossil localities are known globally and of which, the UNESCO World Heritage Site Monte San Giorgio, which extends from Switzerland into Italy, is the most important one. Following the discovery of the occurrence of articulated skeletons of marine reptiles in the local mines, large excavations were organized by Bernhard Peyer from the University of Zurich starting 1924. With this collection of articles, we commemorate the successful excavations and research, which initiated the publication of a series of monographies, mostly on the vertebrates but also on the invertebrates of this locality. Especially with the discovery of several remarkably similar Konservat-Lagerstätten in China, the discoveries from Monte San Giorgio gained global relevance. New methodologies such as computed tomography produced a wealth of new data, particularly on endocranial anatomy of several tetrapods.