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Despite the fact that heteromorph ammonites often show a large range of intraspecific variation, that variation has rarely been quantified. Here, we quantify the intraspecific variation and ontogeny of 85 newly collected specimens of the Hauterivian endemic ammonite genus Aegocrioceras. All specimens were collected from concretions in the recently exposed bed 82 in the clay pit Resse in NW Germany (Lower Saxony Basin). Data for the conch morphology (diameter, whorl height, whorl interspace, rib spacing) were collected in 45° steps using the new software CONCH©. The CONCH© software will be made officially available with this publication. All ammonites were a priori identified as A. bicarinatum or A. semicinctum. An assessment of the intra- and interspecific variation as well as the ontogeny of this assemblage demonstrates the presence of just one species, i.e., A. bicarinatum. Comparison with the type material of A. bicarinatum and A. semicinctum reveals a large morphological overlap of different conch parameters and does not support a separation of both forms as distinct species. The analyzed assemblage of A. bicarinatum has a high variation in conch morphology including whorl interspace, umbilical width, and whorl expansion. Furthermore, the changes in intraspecific variation through ontogeny were quantified and the presence or absence of sexual dimorphism within the assemblage is discussed.

Diurnal vertical migration (DVM) is a widespread phenomenon in the upper ocean, but it remains unclear to what degree it also involves passively transported micro- and meso-zooplankton. These organisms are difficult to monitor by in situ sensing and observations from discrete samples are often inconclusive. Prime examples of such ambiguity are planktonic foraminifera, where contradictory evidence for DVM continues to cast doubt on the stability of species vertical habitats, which introduces uncertainties in geochemical proxy interpretation. To provide a robust answer, we carried out highly replicated randomized sampling with 41 vertically resolved plankton net hauls taken within 26 hours in a confined area of 400 km2 in the tropical North Atlantic, where DVM in larger plankton occurs. Manual enumeration of planktonic foraminifera cell density consistently reveals the highest total cell concentrations in the surface mixed layer (top 50 m) and analysis of cell density in seven individual species representing different shell sizes, life strategies and presumed depth habitats reveals consistent vertical habitats not changing over the 26 hours sampling period. These observations robustly reject the existence of DVM in planktonic foraminifera in a setting where DVM occurs in other organisms.

Understanding the biology of reproduction is important for retracing key evolutionary processes (e.g. speciation and adaptation) in any group of organisms, yet gaining detailed insights often poses a major challenge. Planktonic Foraminifera are a group of globally distributed marine microbial eukaryotes that are important contributors to the global carbon cycle and, due to their fossil record, are widely used as model organisms to investigate the responses of plankton to past environmental changes. The extant biodiversity of planktonic Foraminifera shows restricted distribution patterns and local adaptations of some species, whereas others are cosmopolitan in the world ocean. Hypotheses on their diversification and population dynamics so far entirely rely on the assumption of a nearly exclusively sexual reproduction.So far, reproduction in culture has not been successful under laboratory conditions, and thus details on their life cycle and its influence on the evolution of the group remain unknown. Only the production of flagellated gametes has been observed and is taken as an indication for sexual reproduction. Yet, sexual reproduction by spawning of gametes in the open ocean relies on sufficient gamete encounters to maintain viable populations. This represents a problem especially for unflagellated protists like planktonic Foraminifera, which lack the means of active propulsion and are characterized by low population densities in large areas of the world ocean.To increase the sparse knowledge on the reproductive biology of planktonic Foraminifera, we applied a dynamic, individual-based modelling approach with parameters based on laboratory and field observations. We tested if random gamete encounters under commonly observed population densities are sufficient for maintaining viable populations or if alternative strategies, such as asexual reproduction or synchronization in depth and time, are indispensable to achieve reproduction success. Our results show that a strict synchronization of gamete release in time and/or space seems inevitable for a successful maintenance of populations. We further argue that planktonic Foraminifera optimized their individual reproductive success at the expense of community-wide gene flow, which may explain their high degree of diversity as well as hampered evolvability. Our modelling approach helps to illuminate the ecology and evolution of this important marine calcifier and to predict the existence of necessary reproduction strategies, which may be detectable in future field and laboratory experiments.

Spirula spirula (Coleoidea: Decabrachia) is a unique deep-sea squid with an uncertain taxonomic status. Here, we apply geometric morphometric analyses to precisely describe changes in conch morphology during the course of ontogeny of 21 specimens collected from 12 localities worldwide. These data were used to explore whether the genus is monospecific or comprises several species. Different 2D and 3D conch parameters are presented based on micro-computed tomography data, combining noninvasive imaging techniques with a range of morphometric analyses. Our data imply that Atlantic and Indo-Pacific specimens form two distinct morphological clusters, potentially representing two pseudocryptic species or two populations undergoing divergence (i.e. in the process of speciation). Given the evolutionary trend from straight to more coiled forms, we suggest that S. spirula represents a neotenous form that migrated from the Indo-Pacific towards the Atlantic via the Agulhas leakage, which has been active since the closure of the Strait of Panama (10–3 Ma).

Porosity in planktonic foraminifers (the proportion of the shell surface covered by pores) is a conspicuous quantitative trait, well preserved in fossil shells and implicated as a source of environmental information. Despite its potential, the functional importance of porosity remains poorly understood. It is likely that pores are important in gas exchange, and differences in shell porosity among species or within species may reflect differences in metabolic rates or ambient oxygen concentration. Theoretically, porosity also affects the weight of the shell; and differences in porosity may reflect an adaptation to the specific density of the seawater or differences in allocation of resources to calcification (shell calcification intensity). Finally, there is evidence that porosity may differ between closely related cryptic species. Here we analyzed the potential role of porosity as a regulator of calcification intensity in Orbulina universa by combining biometric measurements based on sediment surface samples from the western Atlantic with a modelling approach. Specimens of O. universa were analyzed concerning their shell size, shell thickness, and shell porosity under light and scanning electron microscopy, and weighed using a microbalance. The resulting empirically derived model shows an effect size of shell thickness that is 7.5 times larger than the effect of shell porosity on the overall shell calcification intensity. This indicates that porosity is unlikely to be used by this species to regulate calcification intensity. By implementing the model on literature data which analyzed calcification intensity in O. universa, we also show that porosity differences among cryptic species in O. universa are unlikely to explain the observed differences in calcification intensity within the species. These findings indicate that functional explanations for differences in porosity in planktonic foraminifers have to be sought outside of calcification or density regulation and, conversely, that the observed differences in calcification intensity are likely driven by shell thickness and their relationship with environmental forcing can be applied without correction for porosity.

Planktonic Foraminifera are widely used for environmental reconstructions through measurements of their shell's geochemical characteristics, including its stable oxygen and carbon isotope composition. Using these parameters as unbiased proxies requires a firm knowledge of all potential confounding factors influencing foraminiferal shell geochemistry. One such parameter is the shell calcification intensity (shell weight normalized for shell size) that may influence the shell delta 18O value either bioenergetically (by reducing energy available and required for equilibrium isotope fractionation during faster calcification) or kinetically (by influencing calcification depth through the shell's density contrast with seawater). Specimens from the Globigerinoides ruber/elongatus compound from a sediment trap in the North Atlantic have been used to quantify the influence of shell calcification intensity on shell delta 18O values. Shell calcification intensity was found to have a significant effect on the shell stable oxygen isotope composition in all species. Through model fitting, it is suggested that the effect size may be in a range of 1 to 2‰ (depending on species, depth migration, and local oceanographic conditions). We show that the confounding effect of shell calcification intensity on stable oxygen isotope composition can be of importance, depending on the anticipated precision of the derived reconstructions. A framework is provided to quantify this effect in future studies.

We have studied benthic foraminiferal assemblages in a marine sediment section (Pefka E section) from the Lindos Bay Formation deposited during the early Pleistocene to provide new insights into the paleo-ecologic and neotectonic evolution of the SE part of the island of Rhodes (NE Mediterranean Sea). Relatively high amounts of eutrophic/low oxygen tolerant species and a comparatively high foraminiferal diversity indicate generally mesotrophic conditions at the sea floor and the presence of well-oxygenated bottom waters. These conditions are attributed to generally elevated surface water productivity and related organic matter fluxes during the early Pleistocene, which is in contrast to the modern oligotrophic conditions in this region. The abundance of individual species shows orbital-driven variability in the obliquity (41 kyr) and precessional (∼23 kyr) bands. Obliquity-driven changes in food availability are indicated by increased percentages of Cassidulina carinata s.l. during marine isotope stages (MIS) 44 and 42, reflecting enhanced food fluxes under glacial conditions. Precession-driven changes are observed for Ca. carinata s.l., Cibicidoides pseudoungerianus s.l., Cibicidoides mundulus and Gyroidinoides altiformis. These changes likely reflect prolonged near-coastal phytoplankton blooms triggered by local fresh-water runoff at times of Northern-Hemisphere insolation maxima, coeval to the formation of sapropels in the adjacent deep-sea basins. The application of a benthic foraminiferal transfer function allowed for the identification of a number of short-term subsidence-uplift cycles, superimposed by overall long-term subsidence of the SE coast of Rhodes. Estimated average uplift and subsidence rates vary between ∼4.2 and ∼10.3 mm/yr. These rates of tectonic motions are distinctly higher compared to most other estimates from Rhodes and suggest a complex neotectonic history of the island during the early Pleistocene, involving both large-scale and local motions associated with alternating compressional and extensional regimes.

Species description in palaeontology is based on the morphology of preserved hard parts. Ammonoids have extensive intraspecific variation of conch shape, ornamentation, size and the morphology of the suture line. However, ammonoid species were usually differentiated and validated from each other on the grounds of subtle morphological differences of the adult stage. This procedure does not account for intraspecific variation or ontogenetic changes. The few available quantitative studies of ammonites have improved our understanding and the way of species description, documenting a wide intraspecific variability in conch parameters. Studies of intraspecific variation are likely not more widespread for three reasons: 1) not enough material from a single bed, 2) poor preservation of the fossil material and 3) it is a time-consuming process. Here we present a new software which significantly reduces the amount of time by 50% or more necessary to measure standard distances for spirally coiled monomorph or heteromorph shells, i.e. diameter, whorl height, whorl interspace, umbilical width, and ornamentation. Our software allows the collection of morphological data in 10, 30 or 45 degree steps. It is possible to collect more data from a single shell to precisely document ontogenetic changes compared to data collected from sectioned specimens. The set of marker placed along the shell outline can be saved as a project file, displaced markers can be corrected, and the project files can be shared with other researchers. Based on basic shell parameters indices and expansion ratios can be calculated. A dataset summarizing the morphology of a collection of heteromorph ammonite shells from the Hauterivian (Lower Cretaceous) heteromorph ammonite genus Aegocrioceras from Northwestern Germany will be presented.

Chitinous arm hooks (onychites) of belemnoid coleoid cephalopods are widely distributed in Mesozoic sediments. Due to their relative abundance and variable morphology compared with the single, bullet-shaped, belemnite rostrum, arm hooks came into the focus of micropaleontologists as a promising index fossil group for the Jurassic–Cretaceous rock record and have been the target of functional, ecological, and phylogenetic interpretations in the past. Based on three well-preserved arm crowns of the Toarcian diplobelidChondroteuthis wunnenbergi, we analyzed the shape of a total of 87 micro-hooks. The arm crown ofChondroteuthisis unique in having uniserial rather than biserial hooks. The first application of elliptic Fourier shape analysis to the arm weapons of belemnoid coleoids allows for the distinction of four micro-hook morphotypes and the quantification of shape variation within these morphotypes. Based on the best-preserved arm crown, we reconstructed the distribution of morphotypes within the arm crown and along a single arm. Our quantitative data support former observations that smaller hooks were found close to the mouth and at the most distal arm parts, while the largest hooks were found in the central part of the arm crown. Furthermore, we found a distinct arm differentiation, as not every arm was equipped with the same hook morphotype. Here, we report the functional specialization of the belemnoid arm crown for the first time and speculate about the potential function of the four morphotypes based on comparisons with modern cephalopods. Our analyses suggest a highly adapted functional morphology and intra-individual distribution of belemnoid hooks serving distinct purposes mainly during prey capture.

International audience; We present paleo-water depth reconstructions for the Pefka E section deposited on the island of Rhodes (Greece) during the early Pleistocene. For these reconstructions, a transfer function (TF) using modern benthic foraminifera surface samples from the Adriatic and Western Mediterranean Seas has been developed. The TF model gives an overall predictive accuracy of ~50 m over a water depth range of ~1200 m. Two separate TF models for shallower and deeper water depth ranges indicate a good predictive accuracy of 9 m for shallower water depths (0–200 m) but far less accuracy of 130 m for deeper water depths (200–1200 m) due to uneven sampling along the water depth gradient. To test the robustness of the TF, we randomly selected modern samples to develop random TFs, showing that the model is robust for water depths between 20 and 850 m while greater water depths are underestimated. We applied the TF to the Pefka E fossil data set. The goodness-of-fit statistics showed that most fossil samples have a poor to extremely poor fit to water depth. We interpret this as a consequence of a lack of modern analogues for the fossil samples and removed all samples with extremely poor fit. To test the robustness and significance of the reconstructions, we compared them to reconstructions from an alternative TF model based on the modern analogue technique and applied the randomization TF test. We found our estimates to be robust and significant at the 95% confidence level, but we also observed that our estimates are strongly overprinted by orbital, precession-driven changes in paleo-productivity and corrected our estimates by filtering out the precession-related component. We compared our corrected record to reconstructions based on a modified plankton/benthos (P/B) ratio, excluding infaunal species, and to stable oxygen isotope data from the same section, as well as to paleo-water depth estimates for the Lindos Bay Formation of other sediment sections of Rhodes. These comparisons indicate that our orbital-corrected reconstructions are reasonable and reflect major tectonic movements of Rhodes during the early Pleistocene.

Using shells collected from a sediment trap series in the Madeira Basin, we investigate the effects of seasonal variation of temperature, productivity, and optimum growth conditions on calcification in three species of planktonic Foraminifera. The series covers an entire seasonal cycle and reflects conditions at the edge of the distribution of the studied species, manifesting more suitable growth conditions during different parts of the year. The seasonal variation in seawater carbonate saturation at the studied site is negligible compared to other oceanic regions, allowing us to assess the effect of parameters other than carbonate saturation. Shell calcification is quantified using weight and size of individual shells. The size-weight scaling within each species is robust against changes in environmental parameters, but differs among species. An analysis of the variation in calcification intensity (size-normalized weight) reveals species-specific response patterns. In Globigerinoides ruber (white) and Globigerinoides elongatus, calcification intensity is correlated with temperature (positive) and productivity (negative), whilst in Globigerina bulloides no environmental forcing is observed. The size-weight scaling, calcification intensity, and response of calcification intensity to environmental change differed between G. ruber (white) and G. elongatus, implying that patterns extracted from pooled analyses of these species may reflect their changing proportions in the samples. Using shell flux as a measure of optimum growth conditions, we observe significant positive correlation with calcification intensity in G. elongatus, but negative correlation in G. bulloides. The lack of a consistent response of calcification intensity to optimum growth conditions is mirrored by the results of shell size analyses. We conclude that calcification intensity in planktonic Foraminifera is affected by factors other than carbonate saturation. These factors include temperature, productivity, and optimum growth conditions, but the strength and sign of the relationships differ among species, potentially complicating interpretations of calcification data from the fossil record.

Using shells collected from a sediment trap series in the Madeira Basin, we investigate the effects of seasonal variation of temperature, productivity, and optimum growth conditions on calcification in three species of planktonic Foraminifera. The series covers an entire seasonal cycle and reflects conditions at the edge of the distribution of the studied species, manifesting more suitable growth conditions during different parts of the year. The seasonal variation in seawater carbonate saturation at the studied site is negligible compared to other oceanic regions, allowing us to assess the effect of parameters other than carbonate saturation. Shell calcification is quantified using weight and size of individual shells. The size–weight scaling within each species is robust against changes in environmental parameters, but differs among species. An analysis of the variation in calcification intensity (size-normalized weight) reveals species-specific response patterns. In Globigerinoides ruber (white) and Globigerinoides elongatus, calcification intensity is correlated with temperature (positive) and productivity (negative), whilst in Globigerina bulloides no environmental forcing is observed. The size–weight scaling, calcification intensity, and response of calcification intensity to environmental change differed between G. ruber (white) and G. elongatus, implying that patterns extracted from pooled analyses of these species may reflect their changing proportions in the samples. Using shell flux as a measure of optimum growth conditions, we observe significant positive correlation with calcification intensity in G. elongatus, but negative correlation in G. bulloides. The lack of a consistent response of calcification intensity to optimum growth conditions is mirrored by the results of shell size analyses. We conclude that calcification intensity in planktonic Foraminifera is affected by factors other than carbonate saturation. These factors include temperature, productivity, and optimum growth conditions, but the strength and sign of the relationships differ among species, potentially complicating interpretations of calcification data from the fossil record.

The work was financially supported by the Deutsche Forschungsgemeinschaft (grant KU 2259/19) and the Natural Environment Research Council of the UK (grants NER/J/S/2000/00860 and NE/D009707/1). Molecular genetic investigations of the highly abundant extant planktonic foraminifera plexus Globigerinella siphonifera/. Globigerinella calida have recently shown this group to be the genetically most diverse one within planktonic foraminifera, separating it into 12 distinct genetic types belonging to three main genetic lineages. Independently, several morphological or physiological variants have been described within the group, but the correlation between the high genetic diversity and the phenotypic variability remains unclear. In this study, we combine genetic data with morphometric analyses of shell shape and porosity of genotyped individuals of the different genetic lineages. Our morphometric measurements suggest a differentiation of three morphotypes within the plexus, two of which possess the elongated chambers described as a typical trait of G. calida. These two morphotypes with elongated chambers are associated with two distinct genetic lineages. The G. calida morphology therefore appears to have evolved twice in parallel. Unexpectedly, we show that the two morphotypes with elongated chambers can be separated from each other by characters seen in the lateral view of their shells. This implies that the taxonomy of the extant members of the genus Globigerinella should be revised. A comparison with the original descriptions and type specimens of members of the genus shows that two genetic types of one major lineage correspond to G. calida. The second group with elongated chambers is associated with a recently diverged genetic type and we propose to reinstate the name Globigerinella radians for this distinct form. The remaining nine of the 12 genetic types correspond to the G. siphonifera morphology, and in the absence of evidence for morphological differentiation, they form a paraphyletic morpho-taxon. Our results highlight the prevalence of parallelism in the evolution of shell morphology in planktonic foraminifera even at the lowest level of relatedness represented by genetic types. Publisher PDF

To examine the sea-surface temperature (SST) evolution during interglacial Marine Isotope Stage (MIS) 11, we compiled a database of 78 SST records from 57 sites. We aligned these records by oxygen-isotope stratigraphy and subjected them to an Empirical Orthogonal Function (EOF) analysis. The principal SST trend (EOF1) reflects a rapid deglacial warming of the surface ocean in pace with carbon dioxide rise during Termination V, followed by a broad SST optimum centered at ~410 thousand years (ka) before present (BP). The second EOF indicates the existence of a regional SST trend, characterized by a delayed onset of the SST optimum, followed by a prolonged period of warmer temperatures. The proxy-based SST patterns were compared to CCSM3 climate model runs for three time slices representing different orbital configurations during MIS 11. Although the modeled SST anomalies are characterized by generally lower variance, correlation between modeled and reconstructed SST anomalies suggests a detectable signature of astronomical forcing in MIS 11 climate trends.

The deep-sea microfossil record is characterized by an extraordinarily high density and abundance of fossil specimens, and by a very high degree of spatial and temporal continuity of sedimentation. This record provides a unique opportunity to study evolution at the species level for entire clades of organisms. Compilations of deep-sea microfossil species occurrences are, however, affected by reworking of material, age model errors, and taxonomic uncertainties, all of which combine to displace a small fraction of the recorded occurrence data both forward and backwards in time, extending total stratigraphic ranges for taxa. These data outliers introduce substantial errors into both biostratigraphic and evolutionary analyses of species occurrences over time. We propose a simple method—Pacman—to identify and remove outliers from such data, and to identify problematic samples or sections from which the outlier data have derived. The method consists of, for a large group of species, compiling species occurrences by time and marking as outliers calibrated fractions of the youngest and oldest occurrence data for each species. A subset of biostratigraphic marker species whose ranges have been previously documented is used to calibrate the fraction of occurrences to mark as outliers. These outlier occurrences are compiled for samples, and profiles of outlier frequency are made from the sections used to compile the data; the profiles can then identify samples and sections with problematic data caused, for example, by taxonomic errors, incorrect age models, or reworking of sediment. These samples/sections can then be targeted for re-study.