This Virtual Special Issue (VSI) entitled Brachiopods: Sentinels of the marine Phanerozoic comprises a diverse set of 15 studies that collectively illuminate the evolutionary, palaeobiological, palaeoecological, and palaeobiogeographical history of brachiopods across more than half a billion years. The VSI arose out of the successful 9th International Brachiopod Congress (IBC/CIB) held at Brock University in St. Catharines, Ontario, Canada, from 24th to 27th June 2024. Papers were invited from the 45 participants (representing 13 countries) and through open call to the global brachiopod community. The major themes of this VSI encompass the topics central to the disciplines that this journal best represents: palaeogeography, palaeoclimatology, and palaeoecology, in addition to palaeobiology, biostratigraphy, and palaeobiogeochemistry. Together, these research papers have a global reach and span mainly the Paleozoic and Mesozoic Eras. We are confident that the papers combined in this VSI will have enduring value, not only to current brachiopodologists, but in their ability to inspire the next generations of brachiopod paleontologists and earth scientists, as well as brachiopod paleobiologists and evolutionary biologists.

Nine brachiopod species belonging to eight genera have been identified in the material from north-western Australia, including Christmas Island. Three species, i.e. Lingula anatina Lamarck, Thecidellina blochmanni Dall, and Frenulina sanguinolenta (Gmelin) have been previously reported from this region. The dominant species in the studied material is the endemic Australian species Jaffaia jaffaensis (Blochmann), which is well known from southern Australia but recorded here for the first time from northern Australia. The remaining species, Dysedrosia borneoensis (Dall), Dallithyris murrayi Muir-Wood, Terebratulina callinome Dall, T. photina Dall, and Jolonica hedleyi Dall are the first records of these species from off Australia. The assemblage from north-western Australia differs markedly in species composition from the brachiopod fauna of southern and eastern Australia and shows affinities to the Indo-NW Pacific brachiopods.

An increasing number of studies have addressed the varied responses of different phylogenetically specific groups to climate change. However, the dominant mechanisms and robust data-driven evidence remain underexplored. This study investigated the environmental resilience of biocalcifiers, with a focus on living brachiopods - organisms that have persisted throughout Earth's geo-history and serve as vital archives of marine life. By analysing the biogeographical patterns of brachiopods, we assessed the influence of temperature on ecomorphological traits such as species richness, environmental tolerance, shell mineralisation and ornamentation, and other shell morphologies. Using the latest comprehensive database and advanced computational tools, including correlation analysis and machine learning, we uncovered moderate relationships between temperature and these traits. Machine-learning models achieved a temperature prediction performance with a root mean squared error (RMSE) of approximately 5 degrees C when incorporating all tested variables. Our findings highlight the significant role of macroevolutionary adaptation history in shaping brachiopod biogeographical patterns, as evidenced by strong Spatial Autocorrelation phenomena of the tested ecomorphological-trait variables. This study not only advances our understanding of brachiopod ecology and biogeography but also contributes to broader discussions on climate change, biodiversity, and the resilience of marine ecosystems. By integrating traditional and novel methodologies, we provide a framework for exploring complex ecological interactions, offering insights into the resilience of marine ecosystems and tackling current global challenges.

Lithium in marine carbonates may hold key information about their temperature of formation and thus of the thermal history of ambient seawater. Here, we present Li/Ca, Mg/Ca, and Sr/Ca results of modern rhynchonelliformean brachiopods from high to low latitudes, shallow to deep and warm to cold seas covering the world's oceans. Craniids as a group incorporate Li into their shell at a faster rate than any other brachiopod group, and due to their paucity will not be considered contributing material. The primary layer calcite of rhynchonelliformean brachiopods, due to the highly variable nature of its Li content, is deemed unsuitable as a proxy. In contrast, the Li/Ca ratios of fibers of the secondary layer within Terebratulida and Rhynchonellida, in conjunction with the innermost calcite of the Thecideida, appear to be free of major influence by growth rate, water depth, seawater pH and salinity. We compiled Li/Ca thermometers based on: 1) second-layer fiber-calcite Li results [2LB, NG = 57], and 2) with additional Li/Ca results of thecideide calcite [2LBT, NG = 60]. The proposed Li/Ca-brachiopod seawater thermometers (linear 1 and 2), which are independent of seawater chemistry, are as follows: T degrees C = 32.85 (+0.52) - 0.670 (+0.014) Li/Ca2LB (mu mol/mol) r2 = 0.978 (1) T degrees C = 34.73 (+0.37) - 0.716 (+0.010) Li/Ca2LBT (mu mol/mol) r2 = 0.987 (2) Brachiopods are important biocalcifiers especially during the Paleozoic, and thus, the proposed Li/Ca thermometer may be an invaluable supplementary tool to the oxygen and clumped isotope thermometers in characterizing its seawater and climate history.

Brachiopods from the lower upper Maastrichtian (Upper Cretaceous) white chalk succession exposed at Chełm (eastern Poland) comprise Lingula cretacea, Isocrania costata, Cryptoporella antiqua, Cretirhynchia sp., Neoliothyrina sp., Carneithyris sp., Terebratulina chrysalis, T. faujasi, T. longicollis, Terebratulina spp., Gisilina sp., Bronnothyris bronni, Magas chitoniformis, Leptothyrellopsis polonicus and ?Aemula sp. This assemblage is relatively poor in terms of taxonomic diversity and specimen abundance and is dominated by stratigraphically long-ranging species. It is best comparable to that from the micromorphic brachiopod Rugia tenuicostata–Meonia semiglobularis Zone as distinguished in the white chalk successions of Denmark and northern Germany, although this zone is usually placed in the upper lower Maastrichtian. The Chełm succession represents a relatively deep-water and ‘benthos-poor’ variety of white chalk deposited in the Boreal Chalk Sea of Europe. The brachiopod assemblage studied is typical of such a habitat, having been controlled largely by the low availability of minute skeletal substrates suitable for brachiopod settlement.

Two brachiopod species, Terebratulina tenuistriata (Leymerie, 1846) and Orthothyris pectinoides (von Koenen, 1984), have been recorded for the first time from the Middle Eocene (Late Lutetian) nummulitic limestone beds in the Darnah Formation at the Wadi Darnah area in Northeast Libya. These brachiopod species are associated here with Nummulites discorbinus (Schlotheim), Nummulites praelyelli (Boukhary and Kamal), and Nummulites bullatus (Schaub) and are widely distributed on this Middle Eocene Nummulites carbonate platform. The two recorded species are common in the Eocene rocks of Europe and the Arabian Gulf. In northern Africa, the brachiopod species Terebratulina tenuistriata (Leymerie) was only recorded from the Middle Eocene (Bartonian) of Egypt, while Orthothyris pectinoides (von Koenen) is firstly recorded from the Middle Eocene of the southern Tethyan Province (NE Libya) in the present work.

Four brachiopod species, i.e., Terebratula cf. styriaca Dreger, Terebratulina retusa (Linnaeus), Megathiris detruncata (Gmelin) and Megerlia truncata (Linnaeus), have been recognised in the Middle Miocene (lower Badenian) deposits at the localities Borac and Borac-Podoli, Carpathian Foredeep, Moravia, Czech Republic. The species M. truncata predominates in the assemblage studied, while M. detruncata is very rare, found only at the locality Borac. Terebratula cf. styriaca and Terebratulina retusa are reported for the first time from the Moravian part of the Carpathian Foredeep. Two types of trace fossils have been observed on the brachiopod shells: drill holes penetrating the shell (ichnogenus Oichnus Bromley) and etching scars, produced by a brachiopod pedicle (ichnogenus Podichnus Bromley and Surlyk).

The study presents new records of brachiopods from the Lower Miocene deposits of the Qom Formation from two sections, Bagh and Ramsheh in the Isfahan province, Central Iran. Three species, i.e. Argyrotheca bitnerae, Joania cordata, and Platidia anomioides, have been identified in the investigated material. All species are present in the Bagh section whereas in the material from Ramsheh A. bitnerae was not found. Although the species recognized here were already described from the Miocene of the Qom Formation, this is their first report from the localities of Bagh and Ramsheh, providing new data on the distribution of brachiopods in the Cenozoic of Iran.

As a potential anti-predatory defensive structure, the shell ornamentation of marine calcifiers is usually used to understand the macro coevolution of the interactions between predators and preys. Marine calcifiers' shell ornamentation complexity is generally believed to vary negatively with latitude and water depth. In this paper, we explored the association between shell ornamentation and latitude/bathymetry using the latest global database of living brachiopods. We found that (1) similar to 59% of living brachiopods species are characterized by smooth shells and that (2) there is no statistically significant linear trend, either positive or negative, between the ornamentation index and latitudes nor with water depths. Both findings are puzzling for living brachiopods as they are sharply contrasted to the patterns of fossil brachiopods whereby the latter, especially Paleozoic brachiopods, are known to exhibit (1) a much greater ornamentation diversity and (2) (at least for the geological periods that have been studied) a linear latitudinal gradient of ornamentation complexity existed. The reasons why living brachiopods have such a high proportion of smooth or weakly ornamented shells and fail to demonstrate an unequivocal linear latitudinal ornamentation gradient were explored and are linked to a multitude of potential factors rather than uniquely only to the predation pressure. Among these, the most plausible factor seems to be the cryptic (refuge-type) habitats (e.g., deep waters, cold polar regions, and submarine rock caves) that living brachiopods have been adapted to due to their low metabolism, where predation pressure is low, allowing brachiopods to enact the predator avoidance strategy rather than having to manufacture robust shell ornamentation to survive in an otherwise highly engaged predator-prey global marine ecosystem.

We describe two new genera of phymaraphiniid lithistid sponges Twertupia gen. nov. and Pickettispongia gen. nov. from the upper Eocene Pallinup Formation of South Western (SW) Australia based on new, rich and very well preserved material. Type material of these two genera, earlier described from poorly preserved material, were originally attributed to Thamnospongia subglabra and Stachyspongia neoclavatela (in case of species of Twertupia), and to Discoderma tabelliformis (case of species of Pickettispongia). This is the first record of bodily preserved phymaraphiniid sponges from Eocene rocks, as well as from the southern hemisphere. We discuss extant and fossil representatives of Phymaraphiniidae and their geographical distribution, concluding that the present day occurrences of these sponges are the result of a much larger Mesozoic Tethyan distribution.

This study presents the new record of brachiopods from the Middle Miocene deposits of the locality of Oslavany, Moravia, Czech Republic. The assemblage contains five species, i.e. Terebratula sp., Megathiris detruncata (Gmelin, 1791), Joania cordata (Risso, 1826), Argyrotheca cuneata (Risso, 1826), and Platidia sp. Apart from the species J. cordata, that dominates in the studied assemblage, the remaining species are reported for the first time from Oslavany. All species recognized here were already recorded from other localities in the Moravian part of the Carpathian Foredeep.

The stable oxygen and clumped isotope composition of brachiopod calcite are important proxies for the reconstruction of Phanerozoic seawater temperatures and delta O-18 values. The utility of brachiopods as a temperature archive is nonetheless challenged by indications that their shells precipitate out of isotopic equilibrium with ambient seawater, though the origin of disequilibrium effects has remained elusive. Here, we apply the recently developed dual clumped isotope thermometer (i.e., the simultaneous measurement of Delta(47) and Delta(48) values in CO2 derived from the acid digestion of carbonates) to modern and fossil brachiopods to investigate disequilibrium signatures recorded in brachiopod calcite. We present evidence that disequilibrium signatures are derived from the combination of two rate-limiting processes: the hydration/hydroxylation of CO2, and, potentially, the diffusion of HCO3-/CO32- in water. An empirical correction for clumped isotope disequilibrium is presented, based on correlation between measured disequilibrium offsets in the Delta(47) and Delta(48) values of modern brachiopods (Delta(47)(disequilibrium) = -0.88 x Delta(48) (disequilibrium) + 0.02). Dual clumped isotope thermometry of Eocene age brachiopods from Seymour Island (similar to 65 degrees S) yields temperatures in agreement with previously reported Delta(47) derived temperatures from coeval bivalves. In contrast, uncorrected Delta(47) derived temperatures from the same brachiopods are 6-11 degrees C colder. Measurement of dual clumped isotope composition alongside delta O-18 values of brachiopod carbonate should also enable more accurate reconstruction of seawater-delta O-18. In comparison with group-specific Delta(47)-temperature calibrations, which correct for an average kinetic bias in Delta(47), dual clumped isotope thermometry accounts for the magnitude of disequilibrium inherent to an individual sample, facilitating more reliable paleotemperature and seawater-delta O-18 reconstructions.

The study presents the first record of Early Oligocene brachiopods from the Lower Red Formation of the Isfahan Province, Central Iran. The assemblage comprises six brachiopod taxa, belonging to five genera, Novocrania Lee and Brunton, Thecidellina Thomson, Argyrotheca Dall, Joania alvarez, Brunton and Long, and Platidia Costa. Two species are described as new, Thecidellina persica sp. nov. and Argyrotheca ramshehensis sp. nov. The discovery of Thecidellina in Iran is the first confirmed occurrence of this genus in Oligocene deposits, filling the gap between known Eocene and Miocene occurrences. At the species level, the brachiopods investigated here show no affinity to those from the Lower Miocene Qom Formation.

Applying Locally Weighted Scatter-plot Smoother (LOWESS) regression, we analysed the global latitudinal diversity patterns of 394 living brachiopod species. We found a consistent bimodal pattern dominated by two mid-latitude peaks located respectively at 35–40°S and 30–35°N (∼warm-temperate zones, WTZs). The bimodality was found to be largely persistent and consistent irrespective of taxonomic, bathymetric and spatial scales. We tested the strength of seven ecological hypotheses thought to potentially explain the classic unimodal latitudinal diversity gradient. The Rapoport's rule was found to be the strongest model fitting the bimodal pattern, followed by the Species-Energy hypothesis. The mechanisms through which the mean latitudinal ranges and thermal niches of living brachiopods may have combined to produce the bimodality are further linked to two other factors: 1) most living brachiopods seem to have a strong adaptation to the mesothermal conditions of the WTZs, and 2) for living brachiopods, the WTZs appear to represent both a source of speciation indicated by a relatively higher per-genus diversification rate and a ‘sink’ of biodiversity due to biogeographic mixing and a concentration of species range-end points.

Thirteen species, belonging to eleven genera, i.e., Discinisca Dall, Novocrania Lee and Brunton, Lacazella Munier-Chalmas, Pliothyrina van Roy, Terebratulina d’Orbigny, Megathiris d’Orbigny, Argyrotheca Dall, Bronnothyris Popiel-Barczyk and Smirnova, Joania Álvarez, Brunton and Long, Platidia Costa and Megerlia King, have been identified in the lower Oligocene rocky-shore deposits at Mammendorf, central Germany. The occurrence of the species Discinisca fallens (Wood), Argyrotheca bitnerae Dulai and Megerlia truncata (Linnaeus) extends their stratigraphic range back to the early Oligocene. The affinity to the early Oligocene brachiopod fauna of the Mainz Basin is noted.

Sponges are well known from recent vents and seeps, but most of them are background organisms that may occur elsewhere. Only a few are proven to be dependent on chemosynthesis. Conversely, sponges are only rarely reported from ancient hydrothermal vent and cold seep deposits. Here we present an overview of present-day sponges reported from such communities, as well as a review of all supposedly vent- and seep-associated fossil sponges reported so far. The most common sponges in the present-day seep and vent communities are Demospongiae, while Hexactinellida are rare. Most of these sponges are considered as “background” fauna with an exception of Cladorhizidae, which may thrive in deep-water hydrothermal vents. The oldest confirmed sponges from ancient seep sites are reported from the Late Jurassic of France and Jurassic/Cretaceous boundary beds in Svalbard. Additionally, we report herein new hexactinellids from Late Cretaceous localities in Japan. The Paleogene and Neogene records of seep sponges are more common but limited mostly to US Pacific Coast. Our review clearly shows that in the fossil record of chemosynthesis-based communities, sponges were equally common and diversified as they are today but were just overlooked.KeywordsCalcareaCambrianCladorhizidaeCretaceousDemospongiaeSponges (extant)Sponges (fossil)HexactinellidaHomoscleromorphaJurassicNeogenePaleogenePoriferaSeepsSpongillinaHydrothermal vents

Three brachiopod species, Terebratulina tenuistriata (Leymerie, 1846), Argyrotheca vidali (Mallada, 1878), and "Terebratula" n. sp., are recognized in the marls and calcareous silts of the Lower Eocene Puebla Formation of the Campo region in the Central Pyrenees, north-eastern Spain. The rich and well preserved material of T. tenuistriata and A. vidali allows to recognize the range of their morphological variability and to evaluate the status of earlier established species. The investigated assemblage is characterized by the small, pedunculate taxa adapted to life on a soft bottom anchoring directly in a soft substrate or attaching to very small, hard substrates.

The global distribution patterns of 14918 geo-referenced occurrences from 394 living brachiopod species were mapped in 5° grid cells, which enabled the visualization and delineation of distinct bioregions and biodiversity hotspots. Further investigation using cluster and network analyses allowed us to propose the first systematically and quantitatively recognized global bioregionalization framework for living brachiopods, consisting of five bioregions and thirteen bioprovinces. No single environmental or ecological variable is accountable for the newly proposed global bioregionalization patterns of living brachiopods. Instead, the combined effects of large-scale ocean gyres, climatic zonation as well as some geohistorical factors (e.g., formation of land bridges and geological recent closure of ancient seaways) are considered as the main drivers at the global scale. At the regional scale, however, the faunal composition, diversity and biogeographical differentiation appear to be mainly controlled by seawater temperature variation, regional ocean currents and coastal upwelling systems.