The International Chronostratigraphic Chart has been under consideration and construction for more than two hundred years. The integration of multidisciplinary, high-resolution studies, and the correlation of pervasive and recognizable markers, have helped develop and continuously update the chart providing a standardized and global language for stratigraphers. STRATI (International Congress on Stratigraphy) is the main scientific meeting of the International Commission on Stratigraphy (ICS) that takes place every four years and is dedicated to all topics associated with improving and updating chronostratigraphy and geochronology. We note that stratigraphical studies are undertaken by specialists who, primarily, focus on specific Phanerozoic systems, rarely venturing beyond the confines of their adopted time slice. Acknowledging this potential weakness, STRATI attempts to remove the intellectual and geological boundaries (disciplinary, taxonomic and temporal), and engage the wider community to define, discuss, combine and compare the potential and role of stratigraphy today in fine tuning the International Chronostratigraphic Chart, especially its correlation and geochronometry. In this Virtual Special Issue (VSI), we present some of the findings of STRATI2023 held in Lille, France (July 11st-13rd 2023) and attended by 285 participants from over 40 countries. Our intention is to collect the most significant contributions arising from this meeting, complemented by specific research articles in order to guarantee a full coverage of the fields of stratigraphy. We demonstrate that refined applied stratigraphy is now approached through a multiproxy perspective, as highlighted in most studies captured here. The VSI goes further by reexamining fundamental concepts in stratigraphy together with the definition of marine bioevents and the role of vertebrates in biostratigraphy. More broadly, the VSI addresses a range of current topics within stratigraphy to highlight the essential role of modern stratigraphical practice as a prerequisite for all future research in palaeogeography, palaeoclimatology and palaeoecology.

The concept of the Global Boundary Stratotype Section and Point (GSSP) to define the bases of chronostratigraphic units, indicated by a spike in rock, has endured for over half a century. Each boundary is defined by a spike in a rock succession, coincident with available biological and or other markers and represents a unique point in time to serve as the standard (yardstick) against which other successions can be correlated. The GSSPs are geological standards, referred to as stratotypes and are key reference points in time. The methodology has brought precision and stability to the definition of geological time, providing a global language for Earth science and Earth scientists. It is the largest cooperative venture in the history of the Earth sciences. In recent years, some challenges to this practice have been voiced questioning the validity of the GSSP concept. It is thus opportune to address misconceptions and misunderstandings and clearly reiterate the necessity of this approach and its success.

The Great Ordovician Biodiversification Event (GOBE) was the largest radiation of marine life in the Phanerozoic, but its causes and consequences remain uncertain, in particular the extent to which environmental change drove biodiversity increase, or vice-versa. Here, we develop high-resolution chemostratigraphic and biodiversity records from South China to show that: the GOBE was initially accompanied by concurrent changes in diversity among plankton, nekton and benthos, suggesting coordinated development of ecological modes during the rapid expansion of marine ecosystems; the onset of the GOBE in the Early Ordovician preceded a major shift in delta 15N during the late Tremadocian to middle Darriwilian, suggesting that marine ecosystem changes drove nutrient cycle evolution in South China, and not the reverse; these changes were associated with an increase in organic matter burial that contributed to drawdown of atmospheric CO2 and long-term climatic cooling through the remainder of the Ordovician. These findings thus provide key insights into the interrelationships between the evolution of marine ecosystems, nutrient cycles, and environmental conditions during the early Paleozoic.

The Lower Carboniferous strata of Breagh oil and gas fields contain abundant oil and gas reserves, and the tight sandstone reservoirs are characterised by extensive bioturbation. The Howick outcrop (Upper Limestone Group, Namurian, Northern England) was selected to investigate the effect of bioturbation on Lower Carboniferous reservoir quality, by analysing its petrological, diagenetic and petrophysical properties. Scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM-EDX) and a petrographic microscope were used for porosity measurement, trace fossil morphological description and lithological analysis. Permeability was measured by spot minipermeametry. Five lithofacies and four bioturbation assemblages were identified. Medium- to coarse-grained sandstones with large-scale planar cross-bedding (Facies SC) are dominated by Skolithos ichnofacies. Bioturbated sandstone intercalated with mudstone (Facies SBM) is characterised by Curvolithus ichnofacies. Nearshore Skolithos ichnofacies is most common in bioturbated ripple-structured sandstone bed topped with mud (FaciesSB), while nearshore Cruziana ichnofacies is commonly observed in bioturbated laminated sandstone with ripple and interrupted ripple structures (Facies SBL) and bioturbation is rare in black coal seams (Facies C). Medium- to coarse-grained sandstone has a higher porosity-permeability; 'Bioturbation reduces the porosity and permeability of Facies SC by approximately 10% and 50%, respectively. Bioturbation improves the porosity more efficiently in originally finer sandstone, increasing it up to 30%. In fine- to very fine-grained sandstone and mudstone, bioturbation not only improves the original porosity and reduces compaction, but also influences permeability by rearranging the distribution of pores and throats and creating new fluid passages for dissolution and cementation. In addition, bioturbation associated with lined or meniscate burrows can decrease reservoir porosity and permeability, while unlined burrows with a simple structure and filling enhance reservoir properties. The study results serve as an effective indicator in the reservoir description and quality analysis of a similar-aged offshore field.

The Great Devonian Interchange (GDI) was a biotic migration event that has been well documented in Euramerica and has only recently been investigated from several localities in Gondwana. This study evaluated the GDI through a Gondwana-first approach, assessing changes in brachiopod bioregionalization during the Early, Middle, and Late Devonian. A presence-absence database of 658 brachiopod genera from 29 depocentres across West and East Gondwana (in addition to peri-Gondwana) was compiled to investigate the migration of these taxa throughout the Devonian and assess the stability of Gondwanan brachiopod bioregions in relation to Devonian biocrises. The time-sliced database was assessed using a variety of multivariate methods, including non-metric multidimensional scaling, as well as cluster and network analyses. Our analyses recovered a consistent two-fold, latitudinal first-order division in Gondwana, comprising a “high-intermediate-latitude” (∼30°-90° S) and a “low-latitude” (∼0°-30° S) bioregion. During the Early-Middle Devonian, the high-intermediate bioregion is latitudinally subdivided into the Colombian-West African (∼30°-50° S), Amazonian (∼50°-70° S) and Malvinoxhosan (∼70°-90° S) regions and the low-latitude bioregion may broadly be divided into a “northwestern Gondwana” and “eastern Gondwana” area. The results further identified the presence of mixing zones between these bioregions, as the Amazonian bioregion, the South Saharan and Sahel Region, and the New Zealand Region appear to have facilitated faunal exchange between high-intermediate and low latitudes during the period. The divisions proposed here do provide some support to the Old World, Eastern Americas, and Malvinoxhosan realms traditionally thought to exist during the Devonian; however, the results indicate that the depocentres of the Old World cannot clearly be clustered into smaller-scale natural groupings, and the depocentres of the Eastern Americas region sustain an admixture of fauna from these traditional bioregions. Furthermore, the findings suggest that the Malvinoxhosan bioregion remains the most well-supported natural grouping among the traditional bioregions, but it subsists as a second-order division within Gondwana during the Devonian. These bioregions gradually collapsed by the Late Devonian, as the extinctions brought about by the GDI and the Devonian biocrises devastated endemic populations. These events are correlated with global warming and pulsed sea-level rise, which brought about anoxic conditions on continental shelves. These events enabled cosmopolitan taxa to proliferate across areas affected by environmental stress, as well as breach previous barriers to migration, allowing them to supersede the niches of endemic and incumbent taxa. There is a trend towards cosmopolitanism among bioregions, clearly observable at lower latitudes in Gondwana; however, faunal exchange to high-latitude bioregions was significantly reduced during the GDI. Thus, the GDI was an exclusively low-latitude event that did not extend to the isolated brachiopod communities of high-latitude Gondwana. Additionally, the dataset suggests that the globally widespread Rhipidothyris is a more suitable marker for the onset of the GDI, whilst Tropidoleptus seems to have been an opportunistic brachiopod which persisted in western Gondwana from the Early Devonian onwards.

A comment on our original paper (Davydov and Lucas, 2026) provided two examples (Devonian/Carboniferous and Permian/Triassic boundaries) to support the assertion that a volcanic ash and its radioisotope date would be the best primary marker for GSSP proposals and correlation. We demonstrate that precise correlation of the base Carboniferous and base Triassic requires the use of all stratigraphic markers including radioisotope dates where available. We reply that there is no practical way to correlate a numerical age in many sections, and that attempting to do so conflates the essential separation of rock and time. However, volcanic ash beds and their ages, are recognized as essential tools for calibration and to test correlations.

Initial studies established the ’Ordovician radiations’ and the ’Great Ordovician Biodiversification Event’ (GOBE) as a key macroevolutionary event in the history of marine life. Nevertheless, to date, with the exception of a few studies, the majority of investigations of the GOBE have been focussed on numerical data from taxonomic counts generally neglecting the ecological processes under the biodiversity curves. Peaks in Ordovician taxonomic biodiversity have been related to fluctuations in ambient settings including climatic conditions, nutrient delivery, oxygen levels together with continental fragmentation and movements and the generation of island arcs. Here, using corrected data from the Paleobiology Database, partitioned into benthos, nekton and plankton together with reef-building organisms, we indicate the major sustained diversifications of these ecological groups during extended Ordovician radiations. Ecological activity under the curve was intense with the post-Cambrian escalation of a range of new lifestyles within the benthos occupying new habitats involving a marked increase in suspension-feeding epifauna and a range of deposit feeders. Marked too was the increase in pelagic carnivorous predators within the vertebrates (chrondrichtheyans and placoderms), the chordates (condontophorids) and molluscs (cephalopods). The benthos, nekton and plankton interacted to establish a more modern marine ecosystem.

Angustothyrididae Dagys, 1972 is a key group of terebratulide brachiopods, because it exhibits characteristics bridging the two major suborders, Terebratulidina and Terebratellidina, and could represent an evolutionary link between them. However, the taxonomy of its type genus, Angustothyris Dagys, 1972, has remained poorly understood. Our restudy of specimens from the Middle Triassic of Hungary and southwestern China, including material from the type localities, reveals that the specimens previously assigned to Angustothyris actually represent multiple genera. This indicates that the diversity of this group has been underestimated, leading us to establish Balatonithyris new genus, Qianothyris new genus, and Angustothyris aszofoensis new species. The long teloform loop in Qianothyris n. gen. fills a morphological gap between short-looped terebratulidines and long-looped terebratellidines, supporting a Late Permian-Triassic origin of the terebratellidines from the Angustothyrididae. The morphological evidence, however, conflicts with molecular data that suggest an earlier divergence between the two suborders. This contradiction implies that either the Angustothyrididae is not the direct ancestor of terebratellidines, or that the terebratellidines are a polyphyletic group with multiple evolutionary origins.UUID: http://zoobank.org/b19352c0-8352-4bba-a0b1-a95963f3da38

Brachiopod species of Gigantoproductus have long fascinated researchers, not only because of their exceptional size and thick shell, but also as unparalleled bioarchives for palaeoecological and palaeoclimatic information. In this paper, we describe faunas containing Gigantoproductus semiglobosus from upper Visean (upper Asbian) successions in two regions of western Ireland, and report geochemical analyses that improve understanding of the palaeobiology of these brachiopods. The two regions are the Burren, where the Aillwee Member (Burren Formation) comprises thick-bedded cyclic bioclastic packstone to grainstone, interpreted as the deposits in predominantly shallow-water (subtidal) marine environments with episodic subaerial exposure, and the Aran Islands, where the Slievenaglasha Formation comprises cyclic crinoidal limestones with chert, deposited in slightly deeper water conditions. Shallowing upward fourth-order cycles in both regions have previously been interpreted as being under a glacioeustatic control. Reconstructed delta 13Corg and delta 15Norg of soft tissues of G. semiglobosus are respectively -29.0 to -30.1 %o (VPDB) and - 1.4 %o and + 6.1 %o (Air) and serve as proxies for identifying photosymbiotic relationships and a mixotroph lifestyle for this species. Well-preserved delta 18Ocarb profiles record high seasonal variations (Delta delta 18O = 0.9 to 1.9 %o corresponding to a Delta T = 4 to 11 degrees C) for palaeoequatorial settings as a far-field proxy of the onset of sustained Gondwanan glaciation in the late Visean and provide evidence of warm tropics during the glaciation. The delta 13Ccarb profiles are mostly controlled by local influences and changes in productivity. Our geochemical analyses of growth patterns, seasonal variation, diet and endosymbiosis in G. semiglobosus, sheds new light on the paradox of these unusual brachiopods, and provides a greater understanding of their massive size.

The Lower Ordovician (Tremadocian) linguliformean brachiopods of the southeastern part of the Anglo-Brabant Massif are documented systematically for the first time. The material belongs to a single Belgian locality (La Roche-en-Brabant), situated in one of the few valleys that incise the Mesozoic-Cenozoic cover, and more precisely from the topmost part of the siliciclastic Mousty Formation (Tangissart Member). Here, minute, poorly diverse linguliformeans are associated with planktic graptolites (Rhabdinopora) and nileid trilobites (Platypeltoides). They consist of three species belonging to three genera (Obolidae and Elkaniidae), of which only Broeggeria is known with certainty, due to the poor preservation of the material. In the Belgian part of the Stavelot-Venn Inlier, the presence of linguliformean brachiopods within the Floian Les Plattes Member of the Ottre Formation, which were reported more than 150 years ago, remains unconfirmed. The genus Broeggeria, known from several Belgian Tremadocian localities, is a relic from the Cambrian brachiopod fauna. By the Tremadocian it is well established globally between the Low-Latitude and High-Latitude provinces. The Belgian assemblage has strong similarities with assemblages from Baltica reflecting the early Palaeozoic changing palaeogeography. center dot Key words: Brachiopoda, Linguliformea, Tremadocian, Floian, Avalonia.

The early Paleozoic was a transformative interval in Earth history, shaped by major macroevolutionary events including the Cambrian Explosion, the Great Ordovician Biodiversification Event (GOBE), and the Late Ordovician Mass Extinction (LOME). Traditional understanding of these events is largely based on a single, aggregated global biodiversity curve, which masks the complex dynamics of individual clades. Here, we deconstruct this global narrative by analyzing speciation, extinction, and diversification patterns for 12 major fossil groups representing multiple ecological guilds using data from the Paleobiology Database and a process-based approach. Our results reveal complex and heterogeneous diversification dynamics that challenge several long-standing views of early Paleozoic macroevolution. Specifically, we demonstrate five key findings: (1) Both the Cambrian Explosion and the GOBE were prolonged radiations, not brief “explosions”, sharing a dynamic of high initial speciation followed by biodiversity accumulation even as rates declined. (2) Despite their similar dynamics, they were fundamentally distinct events driven by different taxonomic groups, with the GOBE's true onset occurring in the Miaolingian—earlier than traditionally recognized. (3) The “Furongian Biodiversity Gap” is an artifact of poor preservation and the faunal dominance of trilobites, not a genuine extinction event. (4) The LOME was a prolonged, 5-million-year crisis with a dual nature, exhibiting a gradual “press” phase in the Katian followed by a catastrophic “pulse” phase in the Hirnantian. (5) The subsequent Silurian recovery was a slow and taxonomically uneven process, lacking a rapid, widespread rebound. Collectively, these findings provide a new, high-resolution evolutionary framework for the early Paleozoic, highlighting that major transitions in the history of life were the composite result of the heterogeneous and asynchronous histories of many individual clades.

The Ordovician (470-443 Ma) witnessed an epic evolutionary trajectory, from the Great Ordovician Biodiversification Event (GOBE) to the Late Ordovician Mass Extinction (LOME), marking an unprecedented rise and fall in biodiversity. Complex interactions among climate, ocean, and geological events, drove fluctuations in the carbon cycle and environmental heterogeneity. Here, we review key developments within this interval pertaining to biological evolution, elemental cycling, climate change, atmospheric composition, and marine redox structure and their mutual interactions. We employ the Community Earth System Model (CESM) to explore the factors underpinning the biotic turnover with a resolution of 10-Myrs time slice. Our simulations suggest that increased organic carbon burial triggered long-term cooling culminating in the Hirnantian ice age, carbon isotopic perturbations, alongside rising atmospheric oxygen and declining COQ. On a secular scale, oxic oceanic water masses expanded worldwide, while the continental seas of the low-latitude landmasses remained oxygen-depleted. The results correspond to a destabilization of oceanic structure with La Nina-like enhanced upwelling in the equatorial region of western flank of Gondwana. This heterogeneous redox structure and reorganization of oceanic currents potentially marked the consequence of one of the most fundamental oceanic oxygenation processes throughout Earth history. This environmental heterogeneity also explains and reconciles discrepancies in estimates of the GOBE duration derived from different palaeobiological databases. Our review and simulations consistently support a dynamic interplay between environmental changes and biotic evolution during the Ordovician.

The majority of studies on mass extinction events (MEEs) have focused on the various extrinsic or palaeoenvironmental killing mechanisms, most associated with habitat destruction and some of which remain hotly contested. The 'mass extinction by insularization and kill' (MEIK) model of this study is proposed as a significant intrinsic cause of the Late Ordovician MEE based on palaeoecological and palaeobiogeographical analyses of Ordovician brachiopod faunas from Laurentia and its adjacent tectonic plates. During the Late Ordovician pulses of a first-order sea-level rise, the MEIK model reveals that biodiversity hotspots shifted from open ocean to epicontinental seas associated with a drastic increase in faunal endemism. Continental-sized 'island faunas', exemplified by the Laurentian intracratonic-sea brachiopods, were characterized by high abundance but relatively low diversity, but more critically the eventual loss of their inter-plate dispersal ability. The onset of mass extinction of these highly endemic 'super-island' faunas, specialized in living in shallow intracratonic seas for similar to 8 million years during the Katian, occurred at the start of the Hirnantian glaciation due to draining of epicontinental seas and loss of their specialized habitats. The data presented here suggest that during a major sea-level rise, global biodiversity epicentres migrated from the ocean to epicontinental seas, becoming genetically isolated, rendering marine shelly benthos intrinsically susceptible to rapid environmental change and subsequent mass extinction.

A centre of radiation for Ordovician bivalves is identified based on an abundant and diverse fauna from the Hsiangyang Formation (Darriwilian, Middle Ordovician) of Dali, western Yunnan, Southwest China. It consists of 22 species of 18 genera including 1) one new genus and four new species: Rhomboconcha tresdentes n. gen. n. sp., Fasciculodonta curvata n. sp., Glyptarca symmetrica n. sp., and Paracyclas initium n. sp.; 2) three taxa known from elsewhere but initially found in Dali: Praeleda sp., Glyptarca sp., and Redonia deshayesi; 3) other taxa previously reported by Fang and Cope (2004). Numerical analysis of the distribution of 11 Middle Ordovician bivalve faunas from different regions shows two distinct faunal groups, the HPL group, representing the bivalves that lived in higher palaeolatitudes, and the LPL group (including Australia and South China) in lower palaeolatitudes. The bivalve fauna from Dali correlates with both groups, indicating that the Indochina Palaeoplate was located between these two groups, and in middle-high palaeolatitudes. Thus, the Indochina Palaeoplate was probably an isolated centre for bivalve radiation during the Middle Ordovician; those genera confined to Dali did not then spread to other palaeoplates. (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.

The International Commission on Stratigraphy (ICS) has been producing and updating its International Chronostratigraphic Chart for several decades. The chart communicates higher-order divisions of geological time and actual knowledge on the numerical ages of their boundaries. Distributed via the ICS website www.stratigraphy.org the chart promotes use in graphic, tabulated and further digital forms in multiple languages. This paper is a status update, eleven years since the last such publication, covering activities between 2012 and 2024. Chart updates during the past decade have echoed the ICSs' primary objective ofprecisely defining a global standard set of time-correlative units (Systems, Series, Stages) for stratigraphic successions worldwide. These units are, in turn, the basis for the Periods, Epochs, and Ages of the Geological Time Scale. Their standardization is fundamental for expressing geological knowledge, in application and education, outreach and continuing research. The chart offers a framework through which regional-scale higher-resolution divisions can be linked, equated and collated. Likewise it offers a framework for digital representation of the Geological Time Scale. Maintenance and distribution of chart versions on the web has been a manual endeavour, a process that ICS is upgrading to serve an increasingly digital world.

The Treatise on Invertebrate Paleontology project still ongoing over more than seventy years is a fine case study for the theme of this special issue on hidden histories in revision of paleontological collections. The history of the foundation and development of the Treatise is discussed together with an outline of how the project operates. Reference is made to those specialists who were contributors and gave of their expertise and time to create a monumental publication of over fifty volumes for the advancement of their science such as Raymond C. Moore who established the series in the 1940s. A selection of hidden histories is provided related to four Treatise volumes and the organization of their planning and revision. Personal accounts provided by paleontologists who held the roles of director of the series and editors/contributors involved in revision of early Treatise volumes on specific groups of invertebrate fossils provide a unique perspective into the organization of these scientific works as well as reflection on their current status and future challenges. This paper on the history and heritage of the Treatise aims to highlight the importance of the “blue, red and green volumes” within taxonomy and systematic invertebrate paleontology as a scientific heritage of the 20 th century and underline the need for future research on the role of the Treatise project in the history of science from the mid twentieth century onwards because to date historiography of this field and practise related to setting standards for classification within invertebrate paleontology is lacking.

The Plectambonitoidea Jones form an abundant and diverse Palaeozoic clade of the phylum Brachiopoda. The shells were generally small and pursued a recumbent mode of life resting on a convex ventral valve or possibly on a concave dorsal valve. A morphological matrix was constructed for the 123 genera comprising the superfamily, based on 43 characters. The changing disparity through time was evaluated from the morphological matrix based on four different metrics and the diversification and diversity dynamics of the clade revealed using corrected range data from the Paleobiology Database. The group expanded its reach during the Tremadocian, accelerating in numbers during the Floian and Dapingian, and peaking in the Darriwilian. The group suffered a major extinction at the end of the Ordovician, continuing as a dead clade walking until the Middle Devonian. On the other hand, the expansion of disparity predated the hikes in diversity, accelerating during the early part of the Ordovician. In common with other major groups of brachiopods, experimentation and innovation amongst new body plans expanded prior to bursts of diversity at lower taxonomic levels.

ABSTRACT The Silurian inliers of the Pentland Hills contain abundant and diverse fossil assemblages and have interested geologists for more than 150 years. However, the faunas are very different from those found in the classic Anglo-Welsh area or the Spanish El Pintado Global Boundary Stratotype Section and Point (GSSP) for the Telychian Stage in peri-Gondwana. Initial geological exploration of the hills found few fossils, with little meaningful interest shown in the area until Dr Archibald Lamont, a controversial Scottish geologist, began researching the inliers. Lamont was the first to suggest that the rocks might be upper Llandovery rather than Wenlock, and went on to propose that their unique fossil assemblages warranted a new division being erected between the Llandovery and Wenlock series, which he named the ‘Pentlandian’. This new division was rejected by the international geological community. Euan Clarkson’s arrival in Edinburgh and his introduction to the Pentland Hills began what would be a lifetime’s fascination with the geology of the area. He instigated an extensive series of research projects and recruited researchers looking at the geology and a wide range of fossil groups, the most abundant of which is the Brachiopoda. The Telychian Wether Law Linn Formation in particular contains many shelly and graptolite faunas enabling correlation. The palaeocommunities identified suggest a deeper-water palaeoenvironment with finer-grained siliciclastic sediments set in a regressive marine sedimentary succession. Multivariate analyses show the mutual proximity of the Pentland associations and their distinctiveness from other Llandovery faunas. The Pentlandian is considered a regional term but the distinctive nature of the Pentlandian biotas, on a global scale, is confirmed and introduced here as the Pentlandian Biotic Complex .