Modern Seas Research Articles

Illuminating the richness of the ascidian fossil record: a new exceptionally diverse assemblage of ascidian spicules from the Middle Miocene of Bosnia and Herzegovina

AbstractAscidians, or sea squirts, are sac‐like sessile tunicates commonly found in modern seas. Although the oldest ascidians, or at least ascidian‐like tunicates, are mid‐Cambrian in age, the quality of the ascidian fossil record is extraordinarily poor. It mostly consists of isolated finds or low‐diversity assemblages, often represented by mineral spicules. Our study reports the world's most diverse assemblage of ascidian spicules, originating from the Middle Miocene Bogutovo Selo near Ugljevik, Bosnia and Herzegovina. This material includes 31 spicule types, with four assignable to species (Lissoclinum cf. perforatum, Polysyncraton cf. bilobatum, Didemnum cf. vexillum and D. cf. leopardi) and 10 to genera, all belonging to aplousobranchiate ascidians. Comparing our findings with those of two other studies that use modern biological nomenclature, our assemblage shows a closer resemblance to the distant Eocene Australian assemblage than to the Miocene ascidians from Eastern Paratethys. This suggests the persistence of a once‐homogeneous and widely distributed Eocene fauna into the Miocene, while the Eastern Paratethyan basin developed an endemic fauna after the isolation of Eastern Paratethys from the open sea. Some taxa of our assemblage currently inhabit the Mediterranean Sea. The discovery of one species in distant South African waters suggests that tectonic and environmental changes during the Late Miocene, including the closure of the Gibraltar Strait and prior disconnection from the Indian Ocean, may have limited its survival to remote refugia. The study underscores the importance of including spicules in reconstructing ascidian faunas in the geological past, an area that has been surprisingly understudied.

Cambrian Oddity: An ancient nozzle-nosed animal lingered in seemingly modern seas.

Cambrian Oddity: An ancient nozzle-nosed animal lingered in seemingly modern seas.

Sedimentation model of the middle Devonian clastic succession of the South Tatar Arch, Pashyian Regional stage, Volga-Ural Oil and Gas Province, Russia

The Pashyian Regional stage (horizon) is the main productive unit of the middle Devonian clastic succession of the South Tatar arch. This article presents, for the first time, maps of the lower and upper parts of the Pashyian, including data on sand-shale ratio, number of sand layers (reservoirs) and thickness, based on the analysis of logging data from 25,000 wells. The maps were created by spatial interpolation of Natural Neighbor and ArcGIS Pro software. The model of sedimentation of the Pashyian Regional stage reflects the interpretation of the plotted maps as well as the synthesis of the results of detailed core investigations (lithological, sedimentological, ichnotextural, petrophysical, etc.) and analysis of archive and published materials. The main points of the proposed model are as follows. The Pashyian sediments were formed in a marine basin, in an environment comparable to that of the middle shelf of modern seas – in an offshore zone dominated by current activity. The basin floor was a relatively flat plateau, on which sandy, silty and clay sediments were simultaneously accumulated. Sediments of all types accumulated during sea transgression. Sea regression caused erosion and destruction of the already formed sediments. Positive landforms of seabed relief, composed predominantly of sandy well-sorted material, comprised autochthonous underwater sand bars, formed by constant currents parallel to the bathymetric contour of the seabed. Underwater sand bars formed extensive systems nearly throughout the entire territory of the modern South Tatar arch. At the same time, allochthonous, poorly sorted, less mature sediments were formed in underwater troughs produced by transversal currents (directed from the shore towards the sea). The proposed model explains the consistent thickness of the Pashyian Regional stage, the mosaic distribution of sand bodies over the area, and the lens-like shape of the sand and siltstone reservoirs. The model can be extrapolated to other stratigraphic intervals of the Devonian clastic succession with similar sedimentological features.

Mitogenomes provide insights into the phylogeny and evolution of brittle stars (Echinodermata, Ophiuroidea)

AbstractOphiuroidea is the most speciose of all classes of Echinoderma. It is an important component in benthic ecosystems, occurring in almost all ecological niches of modern seas. To date, the phylogeny and complete evolutionary history of the ophiuroids have not yet been fully resolved. In this study, we sequenced the complete mitochondrial genomes (mitogenomes) of Ophiothrix (Ophiothrix) exigua and two deep‐sea species Histampica sp. CS049 and Ophioplinthaca sp. M5261. These two deep‐sea ophiuroids displayed reversed strand‐compositional bias and rearranged gene orders. Thirteen distinct patterns of mitochondrial gene order among ophiuroid mitogenomes were detected, with two gene order newly found in Ophiuroidea. Our data supported the gene order found in all sampled Ophiuridae as the most likely ancestral order of all Ophiuroidea. To improve phylogenetic accuracy based on nucleotide differences, two different criteria were used for the analyses: (i) nucleotide sequence from all codon positions (PCG123); (ii) the NTE method (“Neutral Transitions Excluded”) for ameliorating the misleading effects of a reverse strand bias in the data. The two methods confirmed the polyphyly of the orders Ophiacanthida and Amphilepidia. At family and genus level, Ophiuridae, Ophionotus and Ophioplinthus were not monophyletic. The most notable exception was that the NTE phylogeny showed low variation of branch length. NTE dataset generated younger age for most lower‐level nodes than that from PCG123 dataset. All analyses suggested that the ophiuroids radiation occurred around the Permian–Triassic mass extinction event, and the divergence time of the deep‐sea lineages was during the Cretaceous.

Bryozoan–cnidarian mutualism triggered a new strategy for greater resource exploitation as early as the Late Silurian

Bryozoans were common benthic invertebrates in the Silurian seas. The large biodiversity among Silurian benthic organisms prompted diversified interactions, and as a result bryozoans hosted many other organisms as symbionts. Here we analyse the cystoporate bryozoan Fistulipora przhidolensis and unidentified trepostomes intergrown with auloporid tabulate corals and putative hydrozoans. The material comes from the uppermost Přídolí Series (Late Silurian) of the Sõrve Peninsula, Saaremaa, Estonia. Our analysis shows that the interaction was beneficial for both organisms—cnidarians benefited from feeding currents created by the host bryozoan, while the latter benefited from the protection from predators by cnidae, it can thus be classified as mutualism. Such associations are common in modern seas. The analysed organisms are typically encrusting when the symbiosis is absent, when intergrown they display erect, branching morphologies, raised over the substratum, thus exploiting a higher suspension-feeding tier. While similar associations were known from the Devonian, we demonstrate that this novel ecological strategy for greater resource exploitation started as early as the latest Silurian.

High diversity of siliceous sponges in Western Tethyan areas during the Eocene: palaeobiogeographical, ecological and taxonomic significance

AbstractPorifera is a clade of globally distributed, early diverging metazoans that are important components of modern aquatic environments. Despite the fact that they were also abundant in the geological past, their fossil record is uneven. For example, little is known about sponge communities that inhabited the Tethyan areas during the Cenozoic. Here, we record an abundant and taxonomically diverse assemblage of middle–late Eocene sponges from east‐central Ukraine. The material consists of preserved whole‐body specimens as well as disassociated spicules. The taxonomic composition of this new assemblage, supplemented with previously published data obtained from sponge materials originating from the middle and upper Eocene of the East European Platform, documents a surprisingly rich sponge community that inhabited shallow waters (depths of 100 m) and comprised at least 30 demosponge species, including two new taxa, Paratetilla milanek Łukowiak and Theonella alexandriae Łukowiak, three hexactinellids and a single homoscleromorph. Additionally, we report the first fossil occurrence of Vetulina, a demosponge genus that currently is found near the Philippines and Australia and in the Caribbean Sea. Some of the sponge taxa recognized were previously noted from the upper Eocene of Australia and New Zealand. This is indicative of their wide distribution during the early Cenozoic and also shows that a non‐interrupted connection existed between the western Tethyan and peri‐Australian areas, explaining the patchy distribution of some sponge taxa in modern seas.

Hexacoral-crinoid associations from the modern mesophotic zone: Ecological analogues for Palaeozoic associations

Coral-crinoid associations, where a coral overgrew a crinoid's stem, were among the very common Palaeozoic benthic associations, lasting until the end of the Palaeozoic. Many skeletal overgrowths described so far document syn vivo relationships. This type of interaction is unknown from later, Meso- and Cenozoic deposits, and to date has been unknown from recent seas. Here we analysed two individuals of the crinoid Metacrinus rotundus collected from mesophotic depths off the Japanese Pacific coast, overgrown by a single zoantharian polyp of Abyssoanthus sp. (Anthozoa: Hexacorallia: Zoantharia: Abyssoanthidae), and by some sea anemones identified as Metridioidea sp. indet. (Hexacorallia: Actiniaria). These azooxanthellate hexacorals do not possess skeletons, and were located below the host's feeding fan. Our microtomography examinations showed that the anemones did not modify the host's columnals. These specimens offer a good ecological analogue to similar associations of rugose, Cladochonus-like and tabulate corals known from the Palaeozoic. While in our specimens competition for food between hexacorals and crinoid likely does not occur, such interactions are possible. Both zoantharians and sea anemones show similar corallite/oral disc diameters to rugose corals and Cladochonus-like cnidarians that overgrew crinoids in the Palaeozoic, and therefore they probably obtained similar sizes of food particles. In environments with low relief seafloors these hexacorals benefited from their elevated position, and therefore stronger feeding currents. As both Actiniaria and Zoantharia have their phylogenetic roots deep in the Palaeozoic, and coral-crinoid associations are common among Palaeozoic tabulate and rugose corals, we speculate that also Palaeozoic non-skeletal corals, inferred from molecular studies, may have also developed this strategy of settling on crinoids, and therefore occupying similar ecological niches to these hexacorals described here. This report documents that coral-crinoid associations, characteristic of Palaeozoic benthic communities, and thought to have disappeared by the end of Permian, exist in modern seas.

Marine Metazoan Modern Mass Extinction: Improving Predictions by Integrating Fossil, Modern, and Physiological Data.

Evolution, extinction, and dispersion are fundamental processes affecting marine biodiversity. Until recently, studies of extant marine systems focused mainly on evolution and dispersion, with extinction receiving less attention. Past extinction events have, however, helped shape the evolutionary history of marine ecosystems, with ecological and evolutionary legacies still evident in modern seas. Current anthropogenic global changes increase extinction risk and pose a significant threat to marine ecosystems, which are critical for human use and sustenance. The evaluation of these threats and the likely responses of marine ecosystems requires a better understanding of evolutionary processes that affect marine ecosystems under global change. Here, we discuss how knowledge of ( a) changes in biodiversity of ancient marine ecosystems to past extinctions events, ( b) the patterns of sensitivity and biodiversity loss in modern marine taxa, and ( c) the physiological mechanisms underpinning species' sensitivity to global change can be exploited and integrated to advance our critical thinking in this area.

Diversification rates indicate an early role of adaptive radiations at the origin of modern echinoid fauna.

Evolutionary radiations are fascinating phenomena corresponding to a dramatic diversification of taxa and a burst of cladogenesis over short periods of time. Most evolutionary radiations have long been regarded as adaptive but this has seldom been demonstrated with large-scale comparative datasets including fossil data. Originating in the Early Jurassic, irregular echinoids are emblematic of the spectacular diversification of mobile marine faunas during the Mesozoic Marine Revolution. They diversified as they colonized various habitats, and now constitute the main component of echinoid fauna in modern seas. The evolutionary radiation of irregular echinoids has long been considered as adaptive but this hypothesis has never been tested. In the present work we analyze the evolution of echinoid species richness and morphological disparity over 37 million years based on an extensive fossil dataset. Our results demonstrate that morphological and functional diversifications in certain clades of irregular echinoids were exceptionally high compared to other clades and that they were associated with the evolution of new modes of life and so can be defined as adaptive radiations. The role played by ecological opportunities in the diversification of these clades was critical, with the evolution of the infaunal mode of life promoting the adaptive radiation of irregular echinoids.

Taming an ichnotaxonomical Pandora's box: revision of dendritic and rosetted microborings (ichnofamily: Dendrinidae)

Dendritic and/or rosetted microborings in calcareous and osteic skeletal substrates have a diverse trace fossil record, spanning most of the Phanerozoic, whereas the ichnodiversity of comparable bioerosion traces produced in modern seas is rather limited. The most prominent occurrences are known from Devonian brachiopods and from Upper Cretaceous belemnite rostra. Ichnotaxonomically, they are comprised within one of the few ichnofamilies established to date, the Dendrinidae Bromley et al., 2007. As an outcome of the present revision of this ichnofamily, the plethora of 84 ichnospecies established within 25 ichnogenera since the erection of the type ichnogenus Dendrina Quenstedt, 1849 was considerably condensed to 22 ichnospecies included in 7 ichnogenera, based on a coherent morphological categorisation and ichnotaxobasis assessment. The suite of ichnogenera now subsumed within the Dendrinidae includes Dendrina Quenstedt, 1849; Clionolithes Clarke, 1908; Calcideletrix Mägdefrau, 1937; Dictyoporus Mägdefrau, 1937; Abeliella Mägdefrau, 1937; Nododendrina Vogel et al., 1987; and Pyrodendrina Tapanila, 2008. New combinations thereby concern Dendrina dendrina (Morris, 1851) comb. nov., Clionolithes pannosus (Solle, 1938) comb. nov., C. alcicornis (Vogel et al., 1987) comb. nov., C. convexus (Hofmann, 1996) comb. nov., Calcideletrix anomala (Mägdefrau, 1937) comb. nov., C. fastigata (Radtke, 1991) comb. nov., Dictyoporus balani (Tavernier et al., 1992) comb. nov., Nododendrina europaea (Fischer, 1875) comb. nov., N. incomposita (Mägdefrau, 1937) comb. nov. and N. paleodendrica (Elias, 1957) comb. nov. Investigation of new material and a reassessment of 63 dendrinid microborings previously addressed in informal nomenclature allowed the establishment of two complementing ichnogenera, Rhopalondendrina igen. nov. and Antodendrina igen. nov., and eight new ichnospecies, comprising Pyrodendrina arctica isp. nov., P. belua isp. nov., P. villosa isp. nov., Rhopalondendrina avis igen. et isp. nov., R. acanthina igen. et isp. nov., R. contra igen. et isp. nov., R. tigris igen. et isp. nov. and Antodendrina ligula igen. et isp. nov. In densely bioeroded calcareous substrates, different dendrinids and other bioerosion traces may be found in direct contact with each other, forming composite trace fossils, but some of these associations appear rather systematic in nature and could be the work of the same tracemaker under different behavioural modes, thus forming compound trace fossils. In these cases, however, the distinction between the two concepts remains largely equivocal. Dendrinid microborings are primarily found in living and dead calcareous skeletal substrates of bivalves, brachiopods, belemnites and corals, with complementing records from six other substrate types. Facing considerable sampling artefacts, evidence for true substrate specificity or symbiotic relationships is inconclusive as yet, whereas there is direct evidence for post-mortem infestation in several cases, such as the diverse dendrinid associations in Upper Cretaceous belemnite guards. Despite a wealth of available interpretations, the actual biological identity of the dendrinids’ tracemakers remains largely speculative. The most convincing evidence has been put forward in support of foraminiferans as the producers of Nododendrina, and excavating micro-sponges producing Clionolithes and some Calcideletrix. Since most of the dendrinids are found in aphotic (palaeo-)environments, these two principal types of organotrophic tracemakers are also potential candidates for the other ichnogenera. With regards to evolutionary patterns through geologic time, strong adaptive radiations are evident from the ichnodiversity of dendrinid ichnospecies in the Early to Mid-Palaeozoic, reflecting the “Ordovician Bioerosion Revolution” (sensu Wilson & Palmer 2006) and the “Mid-Palaeozoic Precursor of the Mesozoic Marine Revolution” (sensu Signor & Brett 1984), respectively, and in the Mesozoic, coinciding with the prominent “Marine Mesozoic Revolution” (sensu Vermeij 1977). This pattern mimics that of other micro- and macro-bioerosion trace fossils and is interpreted as a reflection of increased predation pressure and consequent infaunalisation. For extinction events, in turn, a differential effect is recorded in that the first four of the “Big Five” mass extinctions appear not to have had any noticeable effect on dendrinid ichnodiversity, whereas the end-Cretaceous mass-extinction resulted in a 77% drop following the Cretaceous peak ichnodiversity of 13 dendrinid ichnospecies.

Megaripples from the Mesoproterozoic of the Kimberley region, northwestern Australia and its geological implications

AbstractLarge ripples are described from the Mesoproterozoic Hilfordy Formation in the Kimberley region, northwestern Australia. Both ripple index (RI) and ripple symmetry index (RSI) suggest the Kimberley ripples were likely generated by storm waves. Their wave height is up to 15–23cm and wave length is up to 70–90cm. These features, incorporated with other morphological characteristics such as symmetry, steepness, ripple spacing, and compositions, agree well with the megaripples previously reported from the intertidal-nearshore settings of modern seas and the geological past. The Mesoproterozoic ripples were likely generated by the storm-induced flows. Literature survey of the global record of megaripples reveals that such structures have occurred through the geological past from the Archean to present day. They were particularly common in the Neoproterozoic and had the largest ripple length and ripple height among the modern and geological records. This is probably because extreme storms prevailed at that time. Their frequent occurrence in present day beach is probably due to the prevalence of extreme storms caused by the monsoon or tsunami/earthquake influenced climatic regimes.

Eocene Varna Reefs in NE Bulgaria

The Varna microbial carbonate reefs, known as the ‘upright stones’, аrе limestone columns of natural origin, formed in the Eocene sands near the town of Varna, NE Bulgaria. These unique geological formations are among the most impressive natural phenomena in Bulgaria and lie in a protected area of 253.3 hectares which includes 18 geosites of aesthetic and scientific value. Some of these features forme part of the ‘Golden Sands’ Natural Park. The upright stones are bacterial-algal reefs formed within non-carbonate Ypresian sands and silts of the Dikilitash Formation. They are of geomorphological, sedimentological and paleontological interest. Human interest in the columns is a result of their unique morphology, due to which they were originally considered to be the remains of ancient temples and castles. According to various theories, these are weathering or infiltration formations, concretions, coral reefs, petrified forests, etc. At the end of the twentieth century, their genesis was studied in the context of a phytogenetic origin, and it was concluded that they are bacterial-algal bioherms similar to recent atolls and miniatols in modern oceans and seas. In support of this hypothesis is the presence of microbial stromatolite laminations and structures, tubular bodies and algal remains in the columns that are not found in the sediments outside of the columns. The Varna reefs are an attractive tourist destination for visitors of the Bulgarian Black Sea coast. These are included in the UNESCO Programme for the protection of geological heritage of scientific value. The future of these unique geological formations depends on their protection at a national and a European level.

Latitudinal variation of brachiopod ornamentation in the Jurassic faunas from the western Tethys and its possible relation to a predation gradient

In modern seas shell ornamentation becomes stronger towards the equator as a response to the increasing predation and a similar relationship was recorded in the case of mid-Palaeozoic brachiopods. It is expected that similar trends and relationship existed in the Jurassic, in the time of the Mesozoic Marine Revolution. The paper describes the latitudinal variation of brachiopod ornamentation in the western part of the Jurassic Tethys and neighbouring epicontinental areas and discusses their relationships to a possible predation gradient. The database included 29 localities (Pliensbachian, Bajocian, Callovian, and Tithonian/Volgian) covering the western Tethyan area from the palaeolatitudes 45° N to 10° S. In the Jurassic western Tethys, the brachiopod ornament was apparently the strongest in the high palaeolatitudes (45° N); decreased in the mid-latitudes and reached high values again near the equator. Considering the anti-predatory function of ornament, and other alternative hypotheses, the present study suggests that in the Jurassic the predation gradient was partly opposite to that of the Palaeozoic. The distribution of two main types of ornament showed opposite trends: spinosity was confined to higher palaeolatitudes whereas ribbing was stronger near the equator. This bipolarity is tentatively interpreted as adaptations to different types of predation; ribbing was a possible tool against durophages, whereas spinosity is supposed to hinder drilling predators.

Stable isotope (δ18O and δ13C) sclerochronology of Callovian (Middle Jurassic) bivalves (Gryphaea (Bilobissa) dilobotes) and belemnites (Cylindroteuthis puzosiana) from the Peterborough Member of the Oxford Clay Formation (Cambridgeshire, England): Evidence of palaeoclimate, water depth and belemnite behaviour

Incremental δ18O and δ13C signals were obtained from three well-preserved specimens of Cylindroteuthis puzosiana and from three well-preserved specimens of Gryphaea (Bilobissa) dilobotes from the Peterborough Member of the Oxford Clay Formation (Cambridgeshire, England). Through-ontogeny (sclerochronological) δ18O data from G. (B.) dilobotes appear to faithfully record seasonal temperature variations in benthic Callovian waters of the study area, which range from c. 14°C to c. 17°C (arithmetic mean temperature c. 15°C). Water depth is estimated to have been in the region of c. 50m, based upon comparisons between these data, previously published non-incremental sea surface δ18O values, and a modern analogue situation. Productivity in Callovian waters was comparable with that in modern seas, based upon δ13C data from G. (B.) dilobotes, with 13C depletion occurring during warmer periods, possibly related to an interaction between plankton blooms and intra-annual variations in mixing across a thermocline. Incremental δ18O data from C. puzosiana provide temperature minima of c. 11°C for all specimens but with maxima varying between c. 14°C and c. 16°C for different individuals (arithmetic mean values c. 13°C). Temperatures for late ontogeny, when the C. puzosiana individuals must have been living close to the study site and hence the analysed specimens of G. (B.) dilobotes, are closely comparable to those indicated by the latter. However, for significant portions of ontogeny C. puzosiana experienced temperatures between c. 2°C and c. 3°C cooler than the winter minimum as recorded by co-occurring G. (B.) dilobotes. Comparisons with modern seas suggest that descent to a depth of c. 1000m would be necessary to explain such cool minimum temperatures. This can be discounted due to the lack of deep waters locally and due to estimates of the depth tolerance of belemnites. The most likely cause of cool δ18O signals from C. puzosiana is a cosmopolitan lifestyle including migration to more northerly latitudes. Mean δ13C values from C. puzosiana are comparable with those from G. (B.) dilobotes. However, the incrementally acquired data are highly variable and probably influenced by metabolic effects. The probable identification of migratory behaviour in C. puzosiana calls into question the reliability of some belemnite species as place-specific palaeoenvironmental archives and highlights the benefits of adopting a sclerochronological approach.

Predation by Drilling Gastropods and Asteroids Upon Mussels in Rocky Shallow Shores of Southernmost South America: Paleontological Implications

To achieve a better understanding of predation pattern recorded in the fossil record it is essential to study predator-prey interactions in the modern seas. It includes the data collected from the field observations as well as from the experiments in captivity. Such an approach allows recognition of the bioeroders, its description and also provides quantification of these interactions. This work offers a case study of the traces of predation resulting from the predator-prey interactions between three mussels: Mytilus chilensis, Brachidontes purpuratus, and Aulacomya atra; and their five natural enemies: the gastropods Trophon geversianus, Xymenopsis muriciformis, and Acanthina monodon, and the asteroids Cosmasterias lurida and Anasterias antarctica living along the intertidal and/or subtidal rocky shores in Tierra del Fuego. The predatory damage to mussel shells varies according to the predator and prey species and techniques for attacking prey are highly specialized. A. monodon drills a hole in B. purpur...

Behavioral and morphological changes caused by thermal stress in the Great Barrier Reef sponge Rhopaloeides odorabile

Climate change is a significant threat to coral reef ecosystems worldwide, with warming oceans having a variety of negative effects on organisms adapted to conditions in modern seas. Increasing sea surface temperatures are predicted to affect many biological processes including sponge heterotrophy. Sponges are a vital component in benthic-pelagic coupling, and therefore these organisms have a significant impact on bacterioplankton communities. Elevated water temperatures may 1) affect sponge pumping behavior by elevating or depressing filtration rates, 2) modify the basic feeding behavior of the sponge, and 3) negatively impact the host's symbiotic microbial communities. Here, we examined the effects of thermal stress on feeding behavior in the common Great Barrier Reef sponge, Rhopaloeides odorabile, primarily focusing on filtration efficiencies and choanocyte chamber characteristics. Temperatures below 31°C had little effect on sponge feeding behavior. At 31°C, however, flow rate, filtration efficiency, and choanocyte chamber density and size were all reduced, and temperatures above 31°C were lethal. Sponges were found to shift feeding preferences towards phototrophic bacteria at 31°C, and there was a strong correlation between pumping rate and choanocyte chamber density. Notably, R. odorabile was able to recover from thermal stress within 48 hours if returned to 27°C. Our results clearly indicate that ecologically realistic temperatures have deleterious effects on sponge feeding behavior.

Coastal dysoxia accompanies Early Miocene warming based on benthic foraminiferal and sedimentary records from Oregon

Abstract The Newport Member of the Astoria Formation, exposed on the central Oregon coast, was deposited at shallow marine depths during the Early Miocene global warming that led to the Middle Miocene Climate Optimum. This record thus provides the opportunity to examine a coastal environment over past warming and ask if the low oxygen conditions observed in recent years on the modern Oregon shelf is a recent phenomenon or a repeated symptom of global warming. Although δ18O variation can be influenced by freshwater flux, if due to temperature δ18O values suggest 2.4–4.5 °C of local warming during deposition of the Newport Member. Species of Buliminacea, Fursenkoina, and Nonionella, abundant in organic-rich, low-oxygen sediments in modern seas, increased in proportional abundance after warming began. In addition, the offset in δ13C values between epifaunal to shallow infaunal taxa and a deeper infaunal species is greater in sediments with higher abundances of these taxa, further supporting increased organic carbon flux. An increase in laminated sediments coincident with these faunal and geochemical changes suggests dysoxic conditions accompanied the increase in organic carbon. Taken together, this multiproxy record suggests that high-organic, low-oxygen, environments developed in shallow waters during Early Miocene warming, perhaps driven by similar upwelling mechanisms thought to drive hypoxia on the modern Oregon coast.

Check-list of holocene brachiopods annotated with geographical ranges of species

All known data on the composition of extant and extinct Pleistocene brachiopods are summarized based on of the author’s identification of domestic and some foreign (Danish, French, German, and Norwegian) collections and published data. The data on 389 species and 114 genera and subgenera of 31 families, 5 orders, and 3 classed are presented. The synonymy of some taxa is considered; some taxa are partly revised. Each species is provided with the data on geographic distribution and, if possible, on the depth range in the modern seas. The data on the time of appearance show that the species composition of Holocene brachiopods was formed mostly in the postglacial time. The oldest records of the species considered are dated Eocene (inarticulate and short-looped terebratulids), Oligocene (thecideids and long-looped terebratulids), and Miocene (rhynchonellids), that is, the time of phased establishment of the modern global thermohaline circulation of surface and deep waters in the seas and oceans.

Intensities of drilling predation of molluscan assemblages along a transect through the northern Gulf of Trieste (Adriatic Sea)

Drilling predation is one of the most studied biotic interactions in the fossil record and potentially controls biodiversity, but its history may be confounded by natural patchiness across environments. This aspect has been inconsistently evaluated. The current study contributes to our understanding of drilling predation in the Northern Adriatic, which has been previously classified as a low-predation setting, and examines the roles of environment, patchiness, and ecology of prey organisms in modern seas. Nearly 49,000 molluscs from two intertidal and six sublittoral bulk samples along a transect in the Gulf of Trieste were analysed for drill frequency (DF) and prey effectiveness (PE), a measure of prey's ability to resist predatory attacks. DF across all samples was 20.6%, but varied between the intertidal (1.4%) and sublittoral (27.4%). Among the latter, DF differed between the delta foreset beds (18.1%) and level bottom muds and sands (∼ 28% each). PE was low in the intertidal (1.1%) and sublittoral (4.5%). Overall DF and PE among the three mud samples varied by nearly 10%, while that within the two sand samples varied little; however, significantly different DFs were observed only among the families Nuculidae, Galeommatidae and Corbulidae in level bottom mud and Cerithiidae in level bottom sand samples. Only Corbulidae displayed significant variation in PE among level bottom mud samples (16.5–43.7%). PE varied significantly between level bottom sand samples only within the families Cerithiidae and Trochidae. Suspension-feeding bivalves and gastropods had the highest DFs (24.3% and 39.1%, respectively), and the value of epifaunal bivalves (32.0%) was nearly twice as high as that of infaunal bivalves (17.9%). DFs of cementing (43.0%) and byssate (27.0%) bivalves were higher than that of recliners (9.9%). Considering their cryptic life habits, parasitic gastropods (20.3%) and commensal bivalves (40.6%) had exceptionally high DF. For each ecological category, PE was highest on suspension-feeding (11.1%), infaunal (15.8%) and cementing (10.5%) bivalves, and on parasitic gastropods (11.9%). DF did not correlate with diversity indices or predator abundance in the sublittoral; therefore, drilling predation probably does not control diversity on the local scale here. DFs support paleoecological theory relating predation to changes in ecological guilds through the Phanerozoic. DFs were highest on suspension feeders, parasites and sessile prey, and were lowest on predators, recliners, and endobenthic molluscs. While cementation likely reduces bivalve susceptibility to durophages, it apparently does not to impede drilling predators. Finally, DF did not vary across size classes in any species examined except Venerupis rhomboides, where the smallest fraction was drilled more often. Additionally, as the proportion of large individuals in our samples was small, disparities in DF across size classes probably did not influence our results. With respect to predation intensity the relatively high DF in the sublittoral, as well as high DF and PE for various taxa and guilds, places the Northern Adriatic Sea among typical Cenozoic shelf environments.

Octocorals as hosts to serpulid‐macroids from the Cretaceous of the Potiguar Basin, Brazil

LethaiaVolume 42, Issue 3 p. 381-382 Octocorals as hosts to serpulid-macroids from the Cretaceous of the Potiguar Basin, Brazil MARTIN ZUSCHIN, MARTIN ZUSCHIN Martin Zuschin [[email protected]], Department of Palaeontology, University of Vienna, Althanstrasse 14, A-1090 Wien, Austria; Holger Gebhardt [[email protected]], Geologische Bundesanstalt, Neulinggasse 38, A-1030 Wien, Austria;Search for more papers by this authorHOLGER GEBHARDT, HOLGER GEBHARDT Martin Zuschin [[email protected]], Department of Palaeontology, University of Vienna, Althanstrasse 14, A-1090 Wien, Austria; Holger Gebhardt [[email protected]], Geologische Bundesanstalt, Neulinggasse 38, A-1030 Wien, Austria;Search for more papers by this author MARTIN ZUSCHIN, MARTIN ZUSCHIN Martin Zuschin [[email protected]], Department of Palaeontology, University of Vienna, Althanstrasse 14, A-1090 Wien, Austria; Holger Gebhardt [[email protected]], Geologische Bundesanstalt, Neulinggasse 38, A-1030 Wien, Austria;Search for more papers by this authorHOLGER GEBHARDT, HOLGER GEBHARDT Martin Zuschin [[email protected]], Department of Palaeontology, University of Vienna, Althanstrasse 14, A-1090 Wien, Austria; Holger Gebhardt [[email protected]], Geologische Bundesanstalt, Neulinggasse 38, A-1030 Wien, Austria;Search for more papers by this author First published: 23 July 2009 https://doi.org/10.1111/j.1502-3931.2009.00176.xCitations: 3Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume42, Issue3September 2009Pages 381-382 RelatedInformation