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Gastropoda are an exceptionally successful group with a rich and diverse fossil record. They have conquered land and freshwater habitats multiple times independently and have dispersed across the entire globe. Since they are important constituents of fossil assemblages, they are often used for palaeoecological reconstruction, biostratigraphic correlations, and as model groups to study morphological and taxonomic evolution. While marine faunas and their evolution have been a common subject of study, the freshwater component of the fossil record has attracted much less attention, and a global overview is lacking. Here, I review the fossil record of freshwater gastropods on a global scale, ranging from their origins in the late Palaeozoic to the Pleistocene. As compiled here, the global fossil record of freshwater Gastropoda includes 5182 species in 490 genera, 44 families, and 12 superfamilies over a total of ~340 million years. Following a slow and poorly known start in the late Palaeozoic, diversity slowly increased during the Mesozoic. Diversity culminated in an all‐time high in the Neogene, relating to diversification in numerous long‐lived (ancient) lakes in Europe. I summarise well‐documented and hypothesised freshwater colonisation events and compare the patterns found in freshwater gastropods to those in land snails. Furthermore, I discuss potential preservation and sampling biases, as well as the main drivers underlying species diversification in fresh water on a larger scale. In that context, I particularly highlight the importance of long‐lived lakes as islands and archives of evolution and expand a well‐known concept in ecology and evolution to a broader spectrum: scale‐independent ecological opportunity. [ABSTRACT FROM AUTHOR]

Aim: Freshwater ecosystems and their biota are severely endangered by global change today, and predicted extinction levels are skyrocketing for many taxa. Most studies have focused on entire clades, while approaches testing for selective extinction risk with respect to ecological traits are rare. As studies are typically based on modern faunas, the generality of the detected patterns in the context of the current biodiversity crisis remains uncertain. We use a dataset of fossil and modern freshwater gastropods to investigate extinction probability in dependence of lifestyle and geographic distribution. Location: Europe, Miocene to present‐day. Methods: We performed generalized linear mixed modelling to test for a relationship between extinction probability and taxonomic group (Caenogastropoda vs. Hygrophila, reflecting different lifestyles) and range size, while using time as random effect. Extinction and survival of modern representatives was predicted based on IUCN conservation status. To identify the types of faunas with elevated extinction risk with respect to lifestyle, we tested for a relationship between the proportion of Caenogastropoda and lake surface area and geological duration using generalized linear models. Results: We found a clear relationship between extinction likelihood and lifestyle, which is linked to differences in range sizes and is independent of geological time. Caenogastropoda are more prone to go extinct. A strong positive relationship between the proportion of Caenogastropoda and geological duration was found, showing that Caenogastropoda are more dominant in long‐lived lakes. Main conclusions: The elevated extinction risk of caenogastropods is linked to their smaller geographic ranges, which reflects their comparably poor colonization ability, and urges enhanced conservation efforts. Their high diversity and high degree of endemism in long‐lived lakes render, especially these archives of evolution important conservators of biodiversity. As most of these lakes are under severe anthropogenic pressure, concerted conservation measures are needed to ensure the survival of their unique biota. [ABSTRACT FROM AUTHOR]

During the early and middle Miocene, the Dinarides Lake System (DLS) was a major hotspot of freshwater mollusk diversity in southeastern Europe. The numerous intramontane lake basins, originating by combined effects of tectonic subsidence and humid climate, accumulated thick lacustrine successions. Diagenetic overprint and leaching of these carbonate-rich deposits have facilitated insights to faunal contents for only a few basins up to the present. We contribute to filling this gap by documenting for the first time a mollusk fauna from the Bugojno Basin in Bosnia and Herzegovina. The fauna originates from a coal-bearing succession representing a gradual flooding of the coastal wetlands followed upwards by the establishment of perennial lacustrine settings in the basin. Our taxonomic analyses documents 17 gastropod and two bivalve species. New to science are IIllyricocongeria forcakovici nov. sp., Prososthenia krijgsmani nov. sp. and Bania goehlichae nov. sp. The palaeoecological analysis based on quantified samples shows distinct shifts in mollusk composition and abundance. The terrestrial taxa are restricted to the coal-bearing interval of the section; melanopsids, neritids and hydrobiids are abundant in deltaic and littoral settings, whereas bivalves are frequent in littoral and sublittoral environments. In line with previous results, which have evidenced a high degree of intralacustrine radiation in the DLS, the Lake Bugojno fauna shows a low to moderate level of similarity to other DLS faunas. The dissimilarity may partly also result from its younger age as suggested by the presence or absence of regional biostratigraphic marker species. [ABSTRACT FROM AUTHOR]

Sediments of the long-lived Lake Nanning in southern China (Guangxi Province) have yielded rich and diversified fossil biota of Oligocene age. The history of research on these fossils is documented herein, and revised lists of the flora and fauna recorded from Lake Nanning are provided. Based on newly collected data, the mollusc fauna and palynology of the lake sediments are assessed. Gastropods (Viviparidae, Stenothyridae), bivalves (Unionidae), ostracods and fish have successfully radiated in Lake Nanning, and developed a variety of endemic species. Shell thickening, spines, carinae, nodes and restricted apertures in bivalves and gastropods are interpreted as armour to prevent predation by giant shell crushing carp. Four different, successive macro-mollusc associations are documented, and can likely be used for relative dating of the lake sediments. Palynomorph assemblages from different lake stages are dominated by cool temperate conifer pollen and freshwater algae. The new findings suggest that the sediments of the Yongning Formation were deposited during or after Eocene–Oligocene cooling and are Oligocene in age. This also supports the biostratigraphy based on rare mammal finds. The fossils of Lake Nanning are outstandingly well preserved and provide a great opportunity to study endemic lake radiations. Besides, the lake sediments are one of the most important Oligocene climate archives of the region. [ABSTRACT FROM AUTHOR]

Abstract: In the Early to Middle Miocene, a series of lakes, collectively termed the Dinaride Lake System (DLS), spread out across the north-western part of the Dinaride–Anatolian continental block. Its deposits, preserved in numerous intra-montane basins, allow a glimpse into the palaeoenvironmental, palaeobiogeographic and geodynamic evolution of the region. Lake Gacko, situated in southern Bosnia and Herzegovina, is one of the constituent lakes of the DLS, and its deposits are excellently exposed in the Gračanica open-cast coal-mine. A detailed study of the sedimentary succession that addresses facies, sediment petrography, geophysical properties, and fossil mollusc palaeoecology reveals repetitive changes in lake level. These are interpreted to reflect changes in the regional water budget. First-order chronologic constraints arise from the integration of radio-isotopic and palaeomagnetic data. 40Ar/39Ar measurements on feldspar crystals from a tephra bed in the upper part of the sedimentary succession indicate a 15.31±0.16Ma age for this level. The reversed magnetic polarity signal that characterises the larger part of the investigated section correlates to chron C5Br of the Astronomically Tuned Neogene Timescale. Guided by these chronologic data and a detailed cyclostratigraphic analysis, the observed variations in lake-level, evident as two ~40-m and seven ~10-m scale transgression–regression cycles, are tuned to ~400-kyr and ~100-kyr eccentricity cycles. From the tuning, it can be inferred that the sediments in the Gacko Basin accumulated between ~15.8 and ~15.2Ma. The economically valuable lignite accumulations in the lower part of the succession are interpreted to indicate the development of swamp forests in conjunction with lake-level falls corresponding to ~100-kyr eccentricity minima. Pedogenesis, rhizoliths and palustrine carbonate breccias in the upper part of the section reveal long-term aridity coinciding with a ~400-kyr eccentricity minimum. Eccentricity maxima are interpreted to trigger lake-level high-stands. These are accompanied by eutrophication events caused by enhanced denudation of the surrounding basement and increased detrital input into the basin. The presented age model proves that Lake Gacko arose during the Middle Miocene Climatic Optimum and that the optimum climatic conditions triggered the formation of this long-lived lake. [Copyright &y& Elsevier]

Life and depositional environments in the sublittoral zone of Lake Pannon, a large, brackish Paratethyan lake from the Late Miocene, were reconstructed from fossils and facies of the Szák Formation. This formation is exposed in several, roughly coeval (9.4–8.9 Ma) outcrops, located along strike of the paleo-shelf-break in northwestern Hungary. The silty argillaceous marl of the formation was deposited below storm wave base, at 20–30 to 80–90 m water depth. The abundance of benthic organisms indicates that the bottom water was usually well oxygenated. Interstitial dysoxia, however, may have occurred immediately below the sediment–water interface, as evidenced by occasional preservation of trace fossils such as Diplocraterion. The fauna comprised endemic mollusks, including brackish cockles of the subfamily Lymnocardiinae, dreissenid mussels ( Congeria), and highly adapted, uniquely large-sized deep-water pulmonate snails (planorbids and lymnaeids). Ostracods were dominated by endemic species and, in some cases, endemic genera of candonids, leptocytherids, cypridids, and loxoconchids. Fish remnants include a sciaenid otolith and the oldest skeletal occurrence of Perca in Europe. The phytoplankton comprised exclusively endemic coccolithophorids, mostly endemic dinoflagellates (prevailingly Spiniferites), and cosmopolitan green algae. The Late Miocene fauna and flora of Lake Pannon were in many ways similar to the modern Caspian biota, and in particular cases can be regarded as its precursor. [ABSTRACT FROM AUTHOR]

Abstract: An integrated stratigraphic study of a Neogene lacustrine succession on the Pag Island (Croatia), combining quantitative pollen analysis, magnetostratigraphy, cyclostratigraphy, biostratigraphy and gamma-ray measurements, provides new insights into orbitally controlled variations in palaeo-vegetation and depositional patterns in the Dinaride Lake System. The quantitative palynological record shows a cyclical pattern of vegetation changes that closely corresponds to sedimentological patterns. The intervals with a high abundance of thermophilous and xeric indicators, suggesting a warm and dry climate, generally coincide with intervals of frequent lignite deposition and shallow lake facies. This suggests that both records are dominantly controlled by variations in past climatic conditions and lake level. Our data show two large-scale warming and shallowing-upward cycles, which are interpreted to be forced by the ~100 kyr eccentricity cycle of the Earth''s orbit. Magnetostratigraphic data of the examined section reveal a long (113 m) reversed polarity interval, followed by a 7 m thick interval of normal polarity at the top. The inferred depositional rate of ~0.3 mm/yr, combined with biostratigraphic constraints by mollusks, suggests that the most logical correlation of the reversed interval is to chron C5Cr. This indicates that the Pag succession was deposited between 17.1 and 16.7 Ma and that it corresponds to the Burdigalian Stage of the Early Miocene, and the regional Karpatian Stage of the Central Paratethys. The high relative percentage of thermophilous pollen taxa, Engelhardia and Taxodium-type being the most prominent, generally indicates a subtropical humid climate for the SW Croatian part of the Dinaride Lake System. The observed warming trend is possibly related to the onset of the Miocene Climatic Optimum. [Copyright &y& Elsevier]

Early Miocene transpressional wrenching yielded a series of NW-SE-elongated pull-apart basins in the Dinarides of Croatia and Bosnia and Herzegovina. They accommodated a huge lake system that gave rise to spectacular endemic mollusk radiation. Lake Sinj, moderately sized at 342 km, flooded the south-westernmost basin of this system. Due to the karstic environment, the hard-water, alkaline, long-lived lake developed a sediment infill with an average thickness of 370 m, dominated by authigenic limestone. The studied section represents the upper third of the basinal infill and provides detailed insights into the critical period of the lake and of the basinal evolution during the final stages of its filling. It comprises two large-scale, shallowing-upward cycles, both starting with fossil-poor limestones, gradually passing into coal-bearing carbonate rocks and coal seams. The fossil-poor intervals are interpreted as phases of repetitive acidification events due to changing lake level, which induced periodic drying and flooding of the uppermost littoral zone inhabited by starfruit ( Damasonium) meadows. The flooding of the aerated, limy mud plain introduced H+ ions from organic-matter decay reactions into the shallow lake. This decreased its pH level, with catastrophic consequences for its biota. The ecosystem then stabilized during the orbitally-forced, dry climate phases. Based on the mollusk record, streams still influenced the marginal lake environment and rich organic-matter production created swamps and mires. The onset of mollusk radiation in the section correlates with stabilized lake alkalinity, as indicated by the disappearance of starfruits, ongoing authigenic carbonate production and by coal seams representing textbook examples for coal formation in alkaline environments. The inferred basinal setting fits well with the pull-apart basin model, pointing to the presence of an extended shallow ramp in front of a steep, fault-induced hillside of the hinterland. [ABSTRACT FROM AUTHOR]