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Ongoing climate change is predicted to trigger major shifts in the geographic distribution of marine plankton species. However, it remains unclear whether species will successfully track optimal habitats to new regions, or face extinction. Here we show that one significant zooplankton group, the radiolaria, underwent a severe decline in high latitude species richness presaged by ecologic reorganization during the late Neogene, a time of amplified polar cooling. We find that the majority (71%) of affected species did not relocate to the warmer low latitudes, but went extinct. This indicates that some plankton species cannot track optimal temperatures on a global scale as assumed by ecologic models; instead, assemblages undergo restructuring and extinction once local environmental thresholds are exceeded. This pattern forewarns profound diversity loss of high latitude radiolaria in the near future, which may have cascading effects on the ocean food web and carbon cycle.

During the Great Ordovician Biodiversification Event (GOBE), the number of marine invertebrate families more than tripled. Fundamental shifts in clade dominance and ecological structure led to the rise of the Palaeozoic Fauna and the second Palaeozoic Ecological Evolutionary Unit (EEU P2 of Sheehan), which revolutionized benthic ecosystems for the next 200 million years. Although general global signals of increased diversity and ecosystem restructuring are known, direct links between these changes are more poorly constrained on high‐resolution local scales. To address this, rhynchonelliformean brachiopod assemblages of the Middle Ordovician Simpson Group (Oklahoma, USA) were assessed before, during and after maximum local diversity increase related to the second global pulse of the GOBE. Stratigraphically constrained brachiopod species occurrence and abundance data were collected for Dapingian‐lower Sandbian strata via field study. Brachiopod assemblages exhibited declining dominance and increasing evenness from the Dapingian through middle Darriwilian stages followed by high volatility in index values during and after the GOBE interval. These patterns document local faunal turnover and shift from EEU P1 to P2. Furthermore, the average species body volume statistically increased over this interval, a pattern that is independent of phylogenetic constraints. Paired increase in mean body size and size disparity is evidence of niche specialization and utilization of additional food resources. Together, changes in body size, evenness and dominance indicate that increasing ecological complexity was coincident with diversification in Oklahoma. This suggests that a common mechanism, such as climate optimization or increased food abundance, was locally responsible for building both taxonomic diversity and ecological complexity during the GOBE.

<p>The marine biological carbon pump is one of the most important mechanism to extract carbon from the atmosphere and export it to the deep-sea and the sediments, and thus take it out from the cycle for millions of years. Today, marine planktonic diatoms are the main element of that pump; however at the beginning of the Cenozoic they were too rare and not diverse enough to have much geochemical significance. Calcareous nannofossils and foraminifera on the other hand were already important components of the carbonate carbon pump; however they also contribute to the alkalinity pump which on shorter timescales have an adverse effect on carbon sequestration. In addition, heterotrophic, amoeboid protists, in particular polycystine radiolarians, are also known to contribute significantly to the carbon export to the deep-sea due to their role in forming rapidly sinking particles of aggregated organic material. We present new diversity reconstructions using the Neptune database (NSB) and case studies focussed on the Late Neogene and the Eocene-Oligocene transition using newly collected full-fauna/flora diversity data. We will then show how the diversity and abundance history of these groups changed throughout the Cenozoic, what the role of climate/oceanographic changes and competition on their evolution was, and, in the end, what consequences their evolution had on the marine carbon cycle.</p>

A major premise of ecological neutral theory is that population size is inversely related to extinction risk. This idea is central to modern biodiversity conservation efforts, which often rely on abundance metrics to partially determine species extinction risk. However, limited empirical studies have tested whether extinction is indeed more probable for species with low abundances. Here we use the fossil record of Neogene radiolaria to test the relationship between relative abundance and longevity (time from first to last occurrence). Our dataset includes abundance histories for 189 polycystine radiolarian species from the Southern Ocean, and 101 species from the tropical Pacific. Using linear regression analyses, we show that neither maximum nor average relative abundance are significant predictors of longevity in either oceanographic region. This suggests that neutral theory fails to explain the plankton ecological-evolutionary dynamics we observe. Extrinsic factors are likely more important than neutral dynamics in controlling radiolarian extinction.

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Lophophaenidae is a clade of polycystine radiolarians that was highly abundant and diverse in the Late Neogene–Recent eastern equatorial Pacific (EEP). Despite their importance in fossil plankton assemblages, lophophaenids have been neglected because of their generally small size, complex morphology, and weak taxonomic framework. These challenges have left many lophophaenid concepts poorly defined or lacking formal description. Here we address this with a review of 101 lophophaenid taxa observed in EEP Middle Miocene–Recent marine sediments. We discuss existing lophophaenid genera Amphiplecta Haeckel 1881, Arachnocorallium Haeckel 1887, Arachnocorys Haeckel 1860, Botryopera Haeckel 1887, Ceratocyrtis Bütschli 1882, Lithomelissa Ehrenberg 1847, Lophophaena Ehrenberg 1847, and Peromelissa Haeckel 1881, including full species lists. We describe Pelagomanes n. gen., 23 new species: ​​Amphiplecta kikimorae n. sp., Arachnocorys jorogumoae n. sp., Botryopera amabie n. sp., Botryopera babayagae n. sp., Botryopera bolotniki n. sp., Ceratocyrtis? chimii n. sp., Ceratocyrtis vila n. sp., Lithomelissa alkonost n. sp., Lithomelissa babai n. sp., Lithomelissa dybbuki n. sp., Lithomelissa sirin n. sp., Lophophaena arie n. sp., Lophophaena casperi n. sp., Lophophaena domovoi n. sp., Lophophaena gozui n. sp., Lophophaena ikiryo n. sp., Lophophaena ikota n. sp., Lophophaena kaonashii n. sp., Lophophaena leshii n. sp., Lophophaena rusalkae n. sp., Lophophaena shishigae n. sp., Lophophaena ushionii n. sp., and Pelagomanes ibburi n. sp., and one new subspecies, Arachnocorys pentacantha wanii n. subsp. In addition, we document 35 taxa in open nomenclature, and revise generic assignments of 10 species. The names of 32 previously-described species are upheld, but with clarified synonymies, discussion, and illustrations. This work contributes a practical framework for identifying tropical Late Neogene–Recent lophophaenid taxa, and demonstrates their rich morphological diversity.