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The Kimmeridgian Alcobaça Formation of the Lusitanian Basin forms a mixed carbonate–siliciclastic unit between basinal deposits of the Abadia Formation, and fluvial–terrestrial strata of the Lourinhã Formation. This study presents >2.5 km of detailed logs of nine outcrop sections of the Alcobaça Formation in its type region. Eight of these sections encircle the Caldas da Rainha Diapir, which was a prominent, emergent, passive salt diapir during the time of deposition. Palaeoenvironments of the unit form a complex mosaic of low- to high-energy, carbonate- or siliciclastic-dominated shallow shelf settings; coastal embayments and lagoons; and coastal plains with rivers, lakes and playas. In the strata, abundant microfauna is often joined by a rich macrofauna, usually dominated by bivalves. Locally, corals, calcareous sponges or oysters form meadows or patch reefs. These autochthonous to parautochthonous remnants of former communities are assigned to 35 benthic macrofaunal associations. The integration of palaeoecological analysis of these associations with microfaunal and sedimentological data provides constraint on their salinity ranges, which range from slightly hypersaline to freshwater. Frequent temporal and spatial salinity fluctuations are attributed to variations in relative sea-level, salt tectonics or climate. The NNE-trending Caldas da Rainha Diapir induced pronounced facies differentiation. Predominantly, non-marine siliciclastic facies in the northwest and carbonate to siliciclastic, marine to brackish facies in the southwest are contrasted by shallow-marine carbonate facies east of the diapir. Comprehensive exposure and well-preserved fossils make the Alcobaça Formation an excellent showcase to demonstrate how biofacies analysis can help to disentangle the interplay of climate changes, sea-level fluctuations and salt tectonics. Based on the improved characterisation of the unit, the Alcobaça Formation is formally defined, and seven members are established.

The Aptian Crato Konservat-Lagerstätte is renowned for its exceptionally preserved fossils in lacustrine laminated limestones. Although previous works on this site include numerous taxonomic studies, its taphonomy remains a subject of debate. Herein, we present new data on the taphonomy of decapod crustaceans preserved in wrinkle laminites, highlighting the role of microbial mats in enhancing fossil preservation. Our results suggest that benthic microorganisms may have promoted protection and organic mineralization of some of the allochthonous to parautochthonous organic remains within the microbial laminites of the Crato lake. Overall, this work provides the first empirical evidence that the preservational pathways of the fossils in the Crato Konservat-Lagerstätte involved microbial mats.

Drill holes provide valuable information about palaeoecological interactions in fossil ecosystems, but the Jurassic drill-hole record is scarce. We report circular drill holes in the infaunal bivalve Eothyasira antiqua(Münster in Goldfuss) from the Pliensbachian grey shales of the Amaltheenton Formation of Franconia, southern Germany. The outcrop of the Amaltheenton Formation at Buttenheim yields a rich bivalve fauna (57 species), which represents a typical soft-bottom community. Eothyasira antiqua, the yet oldest known member of the family Thyasiridae, represents only 1% of the total bivalve specimens from Buttenheim, but shows an exceptionally high frequency of drill holes. With a drilling rate of 81% of the well-preserved articulated specimens, this occurence is unique compared with other drilled bivalve records from the Mesozoic and even from Recent assemblages. The drill holes resemble those of modern naticids with a larger outer opening and are assigned to the ichnospecies Oichnus paraboloides Bromley. Statistical methods show a non-random distribution of the drill holes over the shell surface with a concentration on the central flank. The drill-hole producer was highly efficient in drilling and exhibited a remarkable prey and site-selective behaviour. The drill holes on the moderately deep infaunal Eothyasira suggest that the predator was also infaunal for at least parts of its life and could cope with poorly oxygenated substrate conditions occurring temporarily in the Amaltheenton environment. Drill-hole characteristics point to a gastropod as producer. None of the about 50 gastropod taxa of the Amaltheenton Formation can be associated with the drill holes with certainty, but Hayamia reticulata (Münster) seems to be the most likely candidate. The results of this study support the opinion that drill holes are generally a scarce phenomenon in the Early Jurassic generated by rare, probably highly specialised predators. Preservational biases are considered to have been less important.

The palaeoecology of Spinicaudata, the dominant group of benthic invertebrates in many pre-Cenozoic freshwater environments, remains poorly understood. In analogy with extant taxa, it has been oversimplified and often reduced to shallow, temporary environments characterized by few trophic levels, implying ecological stasis from the Devonian to the Recent. We excavated 43 horizons of the Lower Cretaceous Yixian Formation (Anjiagou and Hengdaozi beds) to evaluate whether spinicaudatan ecology can be simplified to such an extent. Sedimentological evidence suggests general perennial conditions during the excavated lake interval. Based on 33226 specimen counts, we identified three arthropod-dominated macrobenthic associations and two assemblages. Response curves indicate that the spinicaudatan Eosestheria middendorfii was exceptionally tolerant to environmental gradients, followed, in decreasing order, by mayfly larvae, water boatmen and oligochaetes. Many spinicaudatan-yielding layers represent death after reproductive senescence rather than mass-mortality events. Spinicaudatan size varies significantly according to faunal association. A forward stepwise regression model suggests that growth responded to population density and diversity: lower densities and higher diversities triggered fast growth, and vice versa. The proposed strong density effect on carapace size has been corroborated by rearing experiments: as for E.middendorfii, natural log regression provided the best fit for the two extant species Eulimnadia texana and Eocyzicus argillaquus. Hence, E.middendorfii was a tolerant and morphologically variable species adapted to perennial waters and the frequent presence of higher trophic levels. Although there are rare records of extant taxa co-occurring with fish, the described Early Cretaceous environment is commonly not inhabited by extant Spinicaudata.

A total of 93 surface sediment samples were collected to analyze the environmental factors constraining the foraminiferal distribution pattern in the southern South China Sea (SCS). Species distributions and stable isotopic compositions were combined to reveal the controlling factors, such as depth, salinity, substrate, runoff, currents, and cold seep activities. Water depth is the dominant factor controlling both assemblage composition and δ18O of benthic foraminiferal tests. The 1000 m isobath separates the sites into two clusters (Cluster A and B), which are dominated by deep-water species and shallow-water species, respectively. The sites in the deep-water zone (Cluster A) are characterized by lower absolute abundances, species richness and Shannon Index values (a measure of diversity), and higher proportions of planktonic foraminifers compared with the sites in the shallow-water zone (Cluster B). Increasing proportions of agglutinated tests with depth and rapidly decreasing proportions of planktonic foraminifera in the Nansha Trough Basin provide evidence of calcium dissolution occurring at a depth corresponding with previous reports. Oxygen stable isotopes (δ18OB) of benthic foraminifera become more positive with depth only up to 1000 m and remain constant beyond. Differences in the proportion of agglutinated and porcelaneous tests in the shallow-water zone suggest that terrestrial runoff from nearby river systems (Mekong River and northern Borneo rivers) and seasonal surface currents (SCS Southern Cyclonic Gyre and SCS Southern Anticyclonic Gyre) jointly influence the distribution patterns of foraminifera in the study area. Enrichment of planktonic δ18O is a response to cold waters brought by the SCS southern cyclonic gyre during winter. An upwelling current (Winter Natuna Off-Shelf Current) containing higher amounts of organic matter/nutrients contributes to the depleted δ13C of planktonic foraminifera and to the abnormal abundance of foraminifera at the sites within its area of influence. The dominance of the foraminifer Melonis barleeanus at sites belonging to Subcluster A1 and the stable isotope compositions of benthic foraminifera (δ18O > 0, δ13C

Stable isotope (δ 18 O, δ 13 C) analyses of brachiopod and oyster shells from the Gebel Maghara, Egypt, were used to reconstruct the first detailed dataset on peri-equatorial water temperatures during the Middle to Late Jurassic. Throughout this time interval, temperatures remained relatively constant around an average of 25.7 °C. Slightly warmer conditions existed in the Early Bathonian (~ 27.0 °C), while the Kimmeridgian shows the lowest temperatures (~ 24.3 °C). As expected for a tropical palaeolatitude, the seasonality was very low ( 18 O value of seawater).

The 2-m-thick Wood-Log Bed is a highly ferruginous Middle Oxfordian rock unit exposed in the dry bed of the river Tramau in the Wagad Uplift of the eastern Kachchh Basin, western India, and composed of several layers. The bed contains, at several levels, permineralised conifer wood logs, seeds (Carpolites), cones (Araucarites), leaves (Brachyphyllum, Podozamites), possible bennettitalean flowers (?Williamsonia), and abundant wood debris in a poorly sorted muddy sandstone with scattered coarse quartz grains. The wood concentration is interpreted as the result of episodic flash floods in the hinterland situated in the east. Associated with the wood fossils are abundant ammonites which, together with the ferruginous nature of the sediment, point to offshore sediment starvation. Decay of the plant material might have led to widespread anoxia at the sea floor which restricted the benthic macrofauna for much of the time. Thus, the Wood-Log Bed is the product of two processes, episodic flash floods and sediment starvation. Signs of these processes can be seen in age-equivalent sediments throughout the Kachchh Basin.

Clam shrimps have been recognized as a key group for the study of reproductive system evolution, owing to the diversity of sexual systems in extant members. However, there are comparatively little data on fossil taxa. In this study, we reveal the sexual system of the Early Cretaceous clam shrimp Eosestheria middendorfii (Yixian Formation, China). This is the first study that restricts the analysis to a single cohort, minimizing the otherwise considerable impact of ecophenotypic variation within this species. In addition, the presence of egg clutches, which identifies some individuals as either female or hermaphroditic, serves as an independent indicator for sex prior to the statistical treatment of the data. Obligate sexuality (‘dioecy’) is the inferred reproductive system for E. middendorfii and sexual dimorphism accounts for about 10% of the adult shape variation. Carapace shape variation resulting from malformation and deformation is more pronounced than the underlying sexual dimorphism. Subtle sexual dimorphism, smaller and slightly more elongate females, lateral egg clutches, and egg diameters of about 140 μm indicate that E. middendorfii is closely allied with the extant family Cyzicidae.

Bivalves are comparatively rare elements of the benthic faunas of Jurassic and Early Cretaceous lakes of northeastern China. In the past, Arguniella and Sphaerium have been regarded as belonging to the communities that populated the offshore areas of lake Sihetun, represented by the Lower Cretaceous Yixian Formation of western Liaoning. A detailed biostratinomic analysis of these bivalves suggests, however, that they were introduced from marginal lake habitats where they were reworked by storms and occasionally were transported in suspension offshore. Some of these bivalves were dead and settled on the lake floor as single valves or articulated but opened valves (butterfly position). Others were transported alive but died on their arrival at the bottom due to inimical conditions caused by reduced oxygen levels. A similar interpretation is given for articulated valves of Ferganoconcha in thinly bedded siltstones of the Jurassic Daohugou Fossil Beds of Inner Mongolia, which were also carried alive by hyperpycnal flows to their burial site where they died due to lack of oxygen.

The early history on the discovery of the first Chinese crinoid calyx of “Cupressocrinus abbreviatus” (now Halocrinites schlotheimii Steininger, 1831 ) remains unclear. The first record of “C. abbreviatus” was reported by Fritz Frech in 1911. It was included in the fifth and the last volume of the series titled China by the German traveler and explorer Ferdinand Freiherr von Richthofen. The cover page, title page, and prologue are informative; thus, they are explained and translated in detail. Richthofen's specimen is still the oldest documented cupressocrinitid calyx known in China today. Discovery of a second cupressocrinitid specimen confirms the existence of this family in China. Current taxonomic positions of the Chinese specimens are discussed.

Little is known about the palaeoenvironments of the Early Cretaceous lakes of western Liaoning. Uncertainties exist especially about the water depth, water temperatures and annual temperature fluctuations. Here, we analyse the preservation of the most abundant fish of the lakes, the teleost Lycoptera, articulated skeletons of which occur in large concentrations suggestive of mass mortality. Taphonomic features such as degree of disarticulation, orientation patterns and displacement of skeletal elements reveal distinct preservational patterns. They suggest that the water temperature was low during winter and exhibited pronounced seasonal fluctuations. The depth of the lakes was not deep. Possible causes of the fish mortality are discussed, of which anoxia is favoured. This leads to a more refined palaeoenvironmental model for these palaeolakes, which harbour one of the most important Mesozoic Lagerstatten.

Based on newly collected material from the Bajocian–Oxfordian rocks of Gebel Maghara (North Sinai, Egypt) and available published information, the palaeobiogeographic pattern and the dispersal potential of the macrofauna including bivalves, ammonites, corals, and brachiopods are investigated. Both clustering methods and ordination techniques were applied and evaluated. During Bajocian times, G. Maghara occupied an intracratonic setting and was isolated from the main ocean by islands and shallows. These barriers may have limited the dispersal potential of the macrofauna and impeded the faunal exchange with even nearby areas. Although these barriers had disappeared by rejuvenation of faults during an active rift stage in Bathonian times, the same biogeographic patterns continued, which may be related to the global sea level lowstand. By Callovian times, a time of global sea level highstand, in contrast, the fauna of the study area became very similar to that of northeastern Africa. Similarly, diversity and extinction rates increased from the middle Bathonian onward, which may reflect intrusion of cosmopolitan taxa due to the newly established open marine setting and the global sea level highstand. Towards the Oxfordian, lowering of temperature may have limited the dispersal ranges of the macrofauna within the Ethiopian Province. As a result, a southeastern subprovince (Indo–Malagasy) including Tanzania, Madagascar, and India became established. Although the geographic patterns of the different faunal groups exhibit some similarities resulting from abiotic factors such as sea level, climate, and basin topography, biotic characteristics such as life habits and larval development played the dominant role in shaping the distribution pattern. The dispersal potential was highest for ammonites, followed by that of corals and then bivalves. Brachiopods had the lowest dispersal potential.

The taphonomic pathways of “Ephemeropsis trisetalis” nymphs (mayfly larvae) were systematically investigated based on fossils of different preservational types, collected during three high–stratigraphic-resolution (mm to cm) excavations in the Lower Cretaceous Yixian Formation in the Sihetun area of western Liaoning, China. All fossils studied are fully articulated either in three or two dimensions, which indicates that decay was terminated at a stage before the exoskeleton became disarticulated. We conclude that the Jehol organic skeletons represent at least two general types of preservation produced by pyritization and collapse/compression, respectively. The two-dimensional compressions show no evidence for authigenic minerals, but the three-dimensionally preserved fossils are wholly or partially pyritized. Our study also indicates that aluminosilicate clay and pyrite mineralization are closely associated with fossil “Ephemeropsis trisetalis” nymphs, suggesting that both clay and pyrite played ...

The late Kimmeridgian Tereñes Formation, exposed on the coast of Asturias, northern Spain, displays a complex pattern of directed changes of grain size, carbonate content, and skeletal concentrations. In its upper part, here investigated, the formation represents a protected shelf lagoon in which four major facies types are distinguished: The Nanogyra virgula mudstone (1) and the Corbulomima concentrations (2) are characterized by concentrations of small bivalves. The carbonate mudstone (3) contains pseudomorphs after gypsum crystals and thin crusts of gypsum, occasionally in connection with thin microbial layers. Finally, the silty to fine-sandy marlstone and micrite and marly silt (4) is highly bioturbated and contains a moderately diverse benthic macrofauna. These facies indicate a generally quiet environment punctuated by brief episodes of high water energy. Two low-diversity macrobenthic assemblages can be recognized, each of them strongly dominated by a single bivalve taxon. The Nanogyra virgula assemblage exhibits a higher diversity than the near-monospecific Corbulomima assemblage. The former lived in well aerated waters of slightly reduced salinity, and the latter in dysoxic waters of more strongly reduced salinity. The environmental stress responsible for the extremely low species richness and evenness is thought to be multifactorial, produced by reduced salinity, dysoxic conditions, and a soft substrate, and resulted in simple food chains. The eurytopic opportunist Corbulomima was the only element of the shelly macrobenthos that was able to thrive in the shelf lagoon under these conditions. It occurs in countless mm- to cm-thick pavements and shell beds which show evidence of winnowing, influence of weak currents, and occasionally of distal storms, as can be deduced from the orientation pattern of shells. These rhythmic Corbulomima concentrations are explained as reflecting small-scale climatic fluctuations between wetter, stormier conditions leading to mixing of the water masses and enabling colonization of the lagoonal floor by the bivalve, and drier, more tranquil conditions. The latter resulted in a stratified water mass and anoxia at the bottom. Superimposed on this rhythmic alternation are three higher orders of cycles which are partly climatic controlled, partly reflect changes in relative sea level, FG Paläoumwelt, GeoZentrum Nordbayern der Universität Erlangen, Alemania, Bayerische Staatssammlung für Geologie und Paläontologie, Alemania, Instituto Geológico y Minero de España, España, Museo del Jurásico de Asturias, España, Área de Didáctica de las Ciencias Experimentales, Departamento de Educación, Universidad de Cantabria, España

Sedimentological, taphonomic, and palaeoecological analyses of a core from the central Pearl River delta plain allow a detailed reconstruction of the Holocene sedimentological and biological evolution. The marine ingression of the postglacial sea-level rise reached the core site 9,600 years ago and quickly established brackish conditions. Subsequent to a minor regression, water depths and salinity levels peaked between 7,500 and 6,800 years ago. The eventual cessation of the postglacial sea-level rise led to progradation of the delta front and the establishment of fluvial conditions around 4,200 years BP. Subsequent episodic and short-lived marine ingressions can be attributed to shifting delta lobes. While the reconstructed model parallels already established global and regional sea-level curves, the dataset allows further conclusions. The highly fossiliferous core yields abundant bivalves, gastropods, foraminifera and ostracods. Although these fossil groups recur throughout the core, their resolution potentials for palaeoenvironmental reconstructions differ substantially. Bivalves and foraminifera are extremely abundant. However, their very low species richness and high tolerance to environmental fluctuations only allow the reconstruction of the major steps of delta evolution. Gastropods are more diverse (22 taxa) but occur only sporadically, which diminishes their resolution potential. Another problem is the insufficient knowledge on these mm-scale brackish-water molluscs. In the present study, ostracods exhibit the highest resolution potential, which is mainly due to their high abundance and diversity (32 taxa). Although many of the recorded ostracod species are euryoecious with regard to environmental factors such as salinity, substrate, or water depth, the use of palaeocommunity analyses allows the most detailed palaeoenvironmental reconstruction. While the study of molluscs involves considerably less preparation time than that of microfossils, only ostracods reflect all environmental changes present in the studied core.

The study combines the results of stable isotope (δ13C, δ18O) analyses of 187 belemnites, brachiopods, and oysters from the Middle to Upper Jurassic (Upper Callovian to Kimmeridgian) of the Kachchh Basin in western India. Generally, belemnites show lower δ13C and higher δ18O ratios than the benthic fauna. It is proposed that this discrepancy is caused by different life habitats of both groups with belemnites spending major parts of their life in deeper water outside the Kachchh Basin and entering shallow areas only occasionally (e.g., during seasonal migrations to spawning grounds). A mode of life as fast-swimming, nektonic predators similar to many modern squid species seems plausible. The study emphasises that results of stable isotope analyses should be evaluated separately for each fossil group. In addition to the influence of diagenetic alteration, weathering, salinity changes, and sea-level fluctuations, the ecology of the analysed fossil taxa has to be considered. Temperatures calculated from δ18O ratios point to relatively warm conditions around the Middle to Late Jurassic transition with no evidence for a glacial phase which had been proposed for this boundary. A distinct fall in temperatures is observed during the Middle Oxfordian reaching a minimum in the early Late Oxfordian. It is tempting to connect this event with the break-up of Gondwana causing stronger upwelling in the northwestern Tethys or alternatively the influx of polar water by the opening of the Transgondwanan Seaway. However, such connections cannot be verified without further data, preferably from localities in the southern Malagasy Gulf (e.g., Madagascar) and from younger horizons (Kimmeridgian–Tithonian).

Pan, Y., Sha, J., Fursich, F.T., Wang, Y., Zhang, X. & Yao, X. 2011: Dynamics of the lacustrine fauna from the Early Cretaceous Yixian Formation, China: implications of volcanic and climatic factors. Lethaia, Vol. 45, pp. 299–314. The taphonomy and palaeoecology of the famous Lower Cretaceous Jehol biota of northeastern China are two of its least resolved aspects. The biota occurs in lacustrine sediments characterized by abundant volcanic ash layers. The general view is that these tuff layers correlate strongly with vertebrate mass mortality events. However, though aquatic invertebrates also suffered mass mortality, in the majority of cases individuals tend to occur on bedding planes of finely laminated sediments, suggesting that each mass mortality event is not related to volcanic activity. Based on data collected in the course of two excavations at Zhangjiagou and Erdaougou, the role of volcanic activity and other factors that could have controlled the dynamics of the fauna were investigated. Cluster analyses of fossil assemblages from both localities show similar results, and eight fossil communities are recognized. In the lacustrine Yixian Formation, frequent and often severe volcanic activity represented by the abundant tuff layers influenced the water quality, causing repeated collapse of the aquatic ecosystem. Bedding planes with remains of the eight different communities were analysed, each recording the community dynamics of a shallow eutrophic lake system that was most probably controlled by fluctuations of oxygen level related to climate. A mortality model, in which oxygen-level fluctuations play the decisive role, is proposed to explain the existence and distribution of the fossil communities, as well as the unfossiliferous layers. □China, Jehol biota, lacustrine community, mass mortality, palaeoclimate, volcanic activity.

The Upper Kimmeridgian Wattendorf Plattenkalk, the oldest of the Solnhofen-type plattenkalks of southern Germany, has yielded a high number of exceptionally preserved fossils over the past several years. The high number of fossils and the fact that every bedding plane, along which the laminated rocks split, has been equally thoroughly searched for fossils, allow for qualitative as well as quantitative taphonomic investigations. For a quantitative analysis of the Wattendorf lagerstatte, four different taphofacies (A–D) were established by means of euclidean cluster analysis. For this, biostratinomic features of neopterygian fishes, primarily of the genus Tharsis, were recorded. Percentages of the occurrence of these features per layer were determined and clustered into groups of similar patterns. The taphonomic features utilised were bending of the spinal column, completeness, and skeletal articulation. Taphofacies A through D mark a change from a palaeoenvironment with only small extrinsic disturbing factors to a palaeoenvironment characterised by greater disturbance (e.g. bottom currents, fluctuating salinity). At the beginning of plattenkalk deposition, cyclic changes of the palaeoenvironment prevailed with periodic high disturbance, probably caused by storm-induced flows. These events initiated mixing of the supposedly chemically stratified water body. In the upper part of the plattenkalk unit, taphofacies indicative of higher disturbance dominate, suggesting a change from stable to less stable environmental conditions in the plattenkalk basin resulting in disruption of the typical plattenkalk sedimentation. Sporadic oxygenation of bottom waters is also indicated by the style of soft-tissue preservation. Besides typical phosphatisation, a specimen of Palaeohirudo? sp. shows soft-tissue preservation through iron-oxide permineralisation.

The morphological variability of the soft-bottom oysters Ilymatogyra africana (Lamarck, 1801), Costagyra olisiponensis (Sharpe, 1850) and Chondrodonta joannae (Choffat, 1886) from the Cenomanian of eastern Sinai is interpreted in terms of ecophenotypic response to environmental parameters. In I. africana, the influence of coiling and shape of the left valve on the concavity and outline of the right valve can be demonstrated. Type and stability of the substrate also influenced the shell microstructure: In early growth stages, the layers are conformable, becoming unconformable during later growth stages. This unconformity and the pronounced thickening of the dorsal region of the left valve is interpreted to have led to a re-orientation of the organisms in the sediment, thereby protecting them from the danger of becoming buried and of their gills becoming clogged. The three-dimensional spiral growth and high vertical increment of forma typica of I. africana also protected the organisms from becoming buried. The high degree of disarticulation and the concentration of Ilymatogyra shells suggest reworking due to winnowing and bioturbation. In C. olisiponensis, juveniles were cemented to secondary hard substrates, whereas adults were adapted to a free reclining mode of life. Taphonomic analysis of C. olisiponensis shells suggests a lack of reworking and low rates of sedimentation. There exists a relationship between the size of the attachment area and the shell outline and convexity of C. olisiponensis, with a small attachment area occurring in individuals with a wide postero-ventral part and less convex valves and a large attachment area occurring in more elongated shells with strongly convex valves. Chondrodonta shell concentrations occur in various preservational states, which reflect the gradual mixing and mechanical destruction of a former community. Storm-induced waves and currents as well as reduced sediment input were responsible for their formations.

The so-called Jehol Biota, an excellently preserved Early Cretaceous biota consisting of both lacustrine and terrestrial organisms, is one of the most important Mesozoic fossillagerstatten. Although there have been extensive palaeontological studies, little work has been done on the volcanic settings under which the biota was preserved. The Sihetun area is the most famous fossil locality of the Jehol Biota in western Liaoning, and the volcanic succession in that area is the most representative and best studied. We use a case study of the volcanic succession of the Lower Cretaceous Yixian Formation in the Sihetun area to reconstruct the volcanic complexes and their history, to propose a depositional model of the volcanic successions, and to understand the relationship between volcanic activity and fossil preservation in western Liaoning. The volcanic succession comprises four volcanic complexes, each with distinct products; a shield volcano, an intermediate multi-vent center, a volcanic lake (in summit caldera), and finally lava domes. The presence of a caldera is postulated from exposures which suggest the presence of an inner topographic wall, bounding faults, and intra-caldera fill. Frequent volcanic activities and widespread existence of volcanic lakes during the Early Cretaceous are thought to account for the exceptional preservation of invertebrates and vertebrates of the Jehol Biota in western Liaoning.

Phanerozoic trends in shell and life habit traits linked to postmortem durability were evaluated for the most common fossil brachiopod, gastropod, and bivalve genera in order to test for changes in taphonomic bias. Using the Paleobiology Database, we tabulated occurrence frequencies of genera for 48 intervals of ∼11 Myr duration. The most frequently occurring genera, cumulatively representing 40% of occurrences in each time bin, were scored for intrinsic durability on the basis of shell size, reinforcement (ribs, folds, and spines), life habit, and mineralogy.Shell durability is positively correlated with the number of genera in a time bin, but durability traits exhibit different temporal patterns across higher taxa, with notable offsets in the timing of changes in these traits. We find no evidence for temporal decreases in durability that would indicate taphonomic bias at the Phanerozoic scale among commonly occurring genera. Also, all three groups show a remarkable stability in mean shell size through the Phanerozoic, an unlikely pattern if strong size-filtering taphonomic megabiases were affecting the fossil record of shelly faunas. Moreover, small shell sizes are attained in the early Paleozoic in brachiopods and in the latest Paleozoic in gastropods but are steady in bivalves; unreinforced shells are common to all groups across the entire Phanerozoic; organophosphatic and aragonitic shells dominate only the oldest and youngest time bins; and microstructures having high organic content are most common in the oldest time bins.In most cases, the timing of changes in durability-related traits is inconsistent with a late Mesozoic Marine Revolution. The post-Paleozoic increase in mean gastropod reinforcement occurs in the early Triassic, suggesting either an earlier appearance and expansion of durophagous predators or other drivers. Increases in shell durability hypothesized to be the result of increased predation in the late Mesozoic are not evident in the common genera examined here. Infaunal life habit does increase in the late Mesozoic, but it does not become more common than levels already attained during the Paleozoic, and only among bivalves does the elevated late Mesozoic level persist through the Holocene.These temporal patterns suggest control on the occurrence of durability-related traits by individual evolutionary histories rather than taphonomic megabiases. Our findings do not mean taphonomic biases are absent from the fossil record, but rather that their effects apparently have had littleneteffect on the relative occurrence of shell traits generally thought to confer higher preservation potential over long time scales.

Bivalve concentrations are a conspicuous feature of the Upper Jurassic rock succession of the central Lusitanian Basin. In order to illustrate the mode of their formation and their palaeoecological and sequence stratigraphic significance, we describe and interpret in detail 27 assemblages of bivalves based on their taphonomic and ecological features. Bivalve concentrations are particularly widespread in marginally marine, salinity-controlled environments and less common in open shelf settings. Only the Eomiodon and Myophorella concentrations are dominated by a shallow infaunal bivalve; all other concentrations are composed mainly of epi- or endobyssate [Isognomon (Rostroperna), I. (Isognomon), Pteria, Alaperna, Juranomia] and cementing taxa (Praeexogyra, Actinostreon). Most of the concentrations are mono- to paucispecific, except for the highly diverse Alaperna polita–Pteria credneriana concentrations, which occur in nearshore shelf environments. Lack of sorting, a high percentage of articulated shells, and shells preserved in growth position are evidence that, with few exceptions, the concentrations are autochthonous. Main factors leading to their formation are, apart from a gregarious life habit, a high productivity and a reduced rate of sedimentation. Autogenic and allogenic successional stages can be recognized on the basis of their spatial separation. The time involved in the formation of the concentrations is generally in the order of 102–103 years. Due to the lack of compositional changes within concentrations, time-averaging played no or only a minor role, except in the Alaperna polita–Pteria credneriana concentrations. In sequence stratigraphic terms, most of the concentrations are the product of the maximum flooding zone, but in some cases they constitute the transgressive systems tract. Invariably, they are useful tools for defining depositional sequences. Several of the concentrations described here are not restricted to the Lusitanian Basin but also occur elsewhere in the epicontinental seas bordering the northern margin of the Neotethys.

The faunal content of eighteen bedding planes within the Jianshangou Unit of the Lower Cretaceous Yixian Formation of western Liaoning has been analysed in detail in order to understand the environmental and taphonomic framework of this famous lacustrine fossillagerstatte. The bedding planes were excavated within a 3 m thick section, which is composed of laminated mudstones, graded sandstones and mudstones, and horizontally stratified structureless sandstones and tuffs. All investigated bedding planes occur within the laminated mudstone facies and contain elements of the so-called Jehol Biota, in particular the conchostracan Eosestheria ovata, the ephemerid nymph Hexagenites trisetalis and the crustacean Liaoningogriphus quadripartitus. These three faunal elements occur in high abundance, originally possessed chitinous skeletons and are preserved as compressed, faintly mineralized coats or, in the case of Eosestheria, still possess organic material. The specimens do no represent exuviae, but body fossils. The fossils can be grouped into three low diversity associations, each characterized by one of the three taxa. The plan-view orientation of the taxa is invariably random and size frequency histograms are bimodal or polymodal. This indicates that the fauna is autochthonous and that the histograms reflect several recruitment phases. Apparently, the faunal elements suffered seasonal mass mortality caused by anoxic conditions, which became established in the lake during the summer months. Increased humidity during the winter led to mixing of the lake waters, re-establishment of oxic conditions and to deposition of a thin film of sediment. Such environmental conditions were episodically interrupted by flash floods and volcanic ash falls, which may have been responsible for the preservation of the more spectacular elements of the Jehol biota such as birds and feathered dinosaurs.

The graphoglyptid trace fossil Paleodictyon, characterized by a stratiform hexagonal net, is a diagnostic member of the deep-water Nereites ichnofacies and usually found in deep-sea flysch successions. Scattered records of the trace fossil from shallower, lower-shelf-to-upper-slope environments, particularly since the mid-Mesozoic, have been substantially augmented by new data from Upper Triassic and Jurassic sedimentary basins of Iran. Paleodictyon has been found on the soles of mid-to-lower-shelf event beds produced by storm-induced currents and on the soles of prodelta turbidite deposits in the Upper Triassic Nayband Formation of east-central Iran, the lower Middle Jurassic Shemshak Formation of north-central Iran, the Middle Jurassic Kashafrud Formation of the Koppeh Dagh, and the Middle Jurassic Dalichai Formation of the Binalud Mountains. It appears that the bathymetric range of Paleodictyon throughout the Phanerozoic was considerably wider than generally assumed. The observed dominance of ...

At Wattendorf in the northern Franconian Alb, southern Germany, centimetre- to decimetre-thick packages of finely laminated limestones (plattenkalk) occur intercalated between well bedded graded grainstones and rudstones that blanket a relief produced by now dolomitized microbialite-sponge reefs. These beds reach their greatest thickness in depressions between topographic highs and thin towards, and finally disappear on, the crests. The early Late Kimmeridgian graded packstone–bindstone alternations represent the earliest plattenkalk occurrence in southern Germany. The undisturbed lamination of the sediment strongly points to oxygen-free conditions on the seafloor and within the sediment, inimical to higher forms of life. The plattenkalk contains a diverse biota of benthic and nektonic organisms. Excavation of a 13 cm thick plattenkalk unit across an area of 80 m2 produced 3500 fossils, which, with the exception of the bivalve Aulacomyella, exhibit a random stratigraphic distribution. Two-thirds of the individuals had a benthic mode of life attached to hard substrate. This seems to contradict the evidence of oxygen-free conditions on the sea floor, such as undisturbed lamination, presence of articulated skeletons, and preservation of soft parts. However, palaeoecological and taphonomic analyses indicate that the benthic faunal elements are allochthonous having settled out of suspension and thus must have been derived from hard substrate areas of neighbouring topographic highs. Solely the bivalve Aulacomyella, which occurs concentrated on a single bedding plane, may have colonised the plattenkalk depression during brief periods of oxygenation. Alternatively, a pseudoplanktonic mode of life, attached to floating sea weed, is envisaged for the bivalve. The formation of the plattenkalk is related to local and global factors: a drop in relative sea level caused the death of the microbialite-sponge reefs. Restricted circulation in depressions between the crests of the former reefs led to anoxic conditions and the formation of finely laminated sediments stabilised by microbial mats. The small depressions received sediment and skeletal elements of benthic organisms that were swept off neighbouring topographic highs by storms and that entered the depressions partly as turbidity currents, partly as suspension clouds. A rise in the relative sea level finally terminated the restricted circulation in the depressions and closed the taphonomic window that led to the preservation of the plattenkalk biota.

Distinguishing the differential roles of hardpart-input rates and burial rates in the formation of shell beds is important in paleobiologic and sedimentologic studies, because high shelliness can reflect either high population density of shell producers or lack of sediment. The modeling in this paper shows that differences in the relative importance of burial rates and hardpart-input rates lead to distinct patterns with respect to the degree of shelliness and taphonomic alteration in shell beds. Our approach substantially complements other models because it allows computation of both shelliness and assemblage-level alteration. To estimate shelliness, we dissected hardpart-input rates into dead-shell production and shell destruction rates. To estimate assemblage-level alteration, we computed an alteration rate that describes how rapidly shells accrue postmortem damage. Under decreasing burial rates but constant hardpart-input rates, a positive correlation between alteration and shelliness is expec...

Evaluating the relative importance of biotic versus abiotic factors in governing macroevolutionary patterns is a central question of paleobiology. Here, we analyzed patterns of changes in global relative abundances and diversity of ecological groups to infer the role of biological interactions as driving evolutionary forces in mid-Mesozoic macrobenthic marine ecosystems. Specifically, we tested the hypothesis of escalation, which states that macroevolutionary patterns were controlled by an increasing pressure exerted by enemies on their victims. Associated with evidence of increasing levels of predation and biogenic sediment reworking (bulldozing) is an increasing representation of predation- and disturbance-resistant groups in the fossil record. In particular, we observe increasing proportions of mobile organisms; a decline of vulnerable epifauna living freely on the substrate; and a trend toward infaunalization of the benthos. These trends were most pronounced in the paleotropics, i.e., the region where biological activity is thought to have been highest. The observation that these changes affected several biotic traits and occurred within independent clades argues against the overriding role of a single key adaptive innovation in causing shifts in ecological abundance. Also, changes in the abiotic environment cannot explain these faunal patterns because of lacking cross-correlations with physico-chemical parameters such as global sea level, climate, and seawater chemistry. We conclude that in marine benthic ecosystems of the mid Mesozoic, enemy-driven evolution, or escalation, was a plausible and important factor.

Biological veracity of the sharp diversity increase observed in many analyses of the post-Paleozoic marine fossil record has been debated vigorously in recent years. To assess this question for sample-level (“alpha”) diversity, we used bulk samples of shelly invertebrates, representing three major fossil groups (brachiopods, bivalves, and gastropods), to compare the Jurassic and late Cenozoic sample-level diversity of marine benthos. After restricting the data set to single-bed, whole-fauna, bulk samples (n≥ 30 specimens) from comparable open marine siliciclastic facies, we were able to retain 427 samples (255 Jurassic and 172 late Cenozoic), with most of those samples originating from our own empirical work.Regardless of the diversity metric applied, the initial results suggest that standardized sample-level species (or genus) diversity, driven by evenness and/or richness of the most common taxa, increased between the Jurassic and late Cenozoic by at least a factor of 1.6. When the data are partitioned into the three dominant higher taxa, it becomes clear that (1) the bivalves, which dominated the samples for both time intervals, increased in sample-level diversity between the Jurassic and the late Cenozoic by a much smaller factor than the total fauna; (2) the removal of brachiopods, which were a noticeable component of the Jurassic samples, did not significantly affect standardized sample-level diversity estimates; and (3) the gastropods, which were rare in the Jurassic but common in many late Cenozoic samples, contributed notably to the increase in sample-level diversity observed between the two time intervals. Parallel to these changes, the samples revealed secular trends in ecological structure, including Jurassic to late Cenozoic increases in proportion of (1) infauna, (2) mobile forms, and (3) non-suspension-feeding organisms. These trends mostly persist when data are restricted to bivalves.Supplementary analyses indicate that these patterns cannot be attributed to sampling heterogeneities in paleolatitudinal range, lithology, or paleoenvironment of deposition. Likewise, when data are restricted to samples dominated by species with originally aragonitic shells, the observed temporal changes persist at a comparable magnitude, suggesting that the pervasive loss of aragonite in the older fossil record is unlikely to have been the primary cause of the observed patterns. The comparable ratio of identified to unidentified species and genera, observed when comparing the Jurassic and late Cenozoic samples, indicates that the relatively poorer (mold/cast) preservation of Jurassic aragonite species also is unlikely to have been responsible for the observed patterns. However, the diagenesis-related taphonomic and methodological artifacts cannot be ruled out as an at least partial contributor to the observed post-Paleozoic changes in diversity, taxonomic composition, and ecology (the outcomes of the three tests of the diagenetic bias available to us are incongruent).The study demonstrates that the post-Paleozoic trends in the sample-level diversity, ecology, and taxonomic structure of common taxa can be replicated across multiple studies. However, the diversity increase estimated here is much less prominent than suggested by many previous analyses. The results also narrow the list of causative explanations down to two testable hypotheses. The first isdiagenetic bias—a spurious trend driven by either (a) increasing taphonomic loss of small specimens in the older fossil record or (b) a shift in sampling procedures between predominantly lithified rocks of the Mesozoic and predominately unlithified, and therefore sievable, sediments of the late Cenozoic. The second hypothesis isgenuine biological changes—macroevolutionary trends in the structure of marine benthic associations through time, consistent with predictions of several related models such as evolutionary escalation, increased ecospace utilization, and the Mesozoic marine revolution. Future studies should focus on testing these two rival models, a key remaining challenge for identifying the primary causative mechanism for the long-term changes in sample-level diversity, ecology, and taxonomic structure observed in the Phanerozoic marine fossil record.

The Middle Jurassic sedimentary succession of the Kachchh Basin shows significant changes in lithology, faunal content and diversity across the Bathonian–Callovian boundary. The change in lithology from predominantly carbonates in the Middle and Late Bathonian to siliciclastics in the Callovian is accompanied by a drop in species diversity from high to moderate. Characteristic faunal elements of the Bathonian (corals, sponges, the bivalves Eligmus and members of the Opinae) are absent or rare in the Callovian. In contrast, Callovian sediments contain comparatively high proportions of nuculid bivalves. The clay mineral assemblage reveals prominent variations in the smectite vs. kaolinite abundance, especially during the Bathonian to Callovian transition. From the Bajocian to the Middle Bathonian, smectite becomes the dominant clay mineral and is nearly exclusively present in the Late Bathonian. Towards the Middle Callovian, its content gradually decreases and kaolinite becomes the dominant clay mineral. Illite generally is only a minor component throughout the Middle Jurassic. Based on these results, the Bajocian to Middle Bathonian time interval is interpreted to represent subtropical climatic conditions with seasonal droughts and a moderate supply of terrigenous clastics to the basin. The Late Bathonian was a period with a semi-arid climate, hot seasonal droughts and a minor input of terrigenous clastics. The increase in kaolinite contents in the Callovian suggests a subtropical humid climate with less prominent seasonal droughts and a higher input of siliclastics into the basin accompanied by a higher nutrient influx. Oxygen isotope ratios measured on Bathonian to early Callovian brachiopod shells give palaeotemperatures of 19–24 °C. Callovian to Oxfordian paleotemperatures calculated from oxygen isotopes measured on belemnite rostra range from 11 to 21 °C. The lower palaeotemperatures estimated from the oxygen isotopic composition of belemnite calcite are explained by assuming that the belemnites spent most of their life span in colder regions of the Malagassy Gulf and migrated into the warmer subtropical waters of the Kachchh Basin. Combining these various lines of evidence, the changes in lithology and faunal composition taking place in the Kachchh Basin during the Middle Jurassic appear to reflect largely a change towards increasing humidity rather than a distinct decrease in water temperature.

Upper Jurassic and Lower Cretaceous siliciclastic shallow water sediments of the Kachchh Basin, western India, form strongly asymmetric coarsening-upward cycles, which are interpreted as recording changes in relative sea level (deepening–shallowing cycles). These cycles correspond to depositional sequences, in which deposits of the lowstand systems tract are not present, the sequence boundary coinciding with the transgressive surface. Shell concentrations are found in the transgressive lags at the base of the transgressive systems tract (TST), in the maximum flooding zone (MFZ), and at or close to the top of the highstand systems tract. They belong to six assemblages, five of them dominated by large bivalves such as Seebachia, Herzogina, Gryphaea, Gervillella, Megacucullaea, Pisotrigonia and Indotrigonia, the sixth by the coral Amphiastraea. Three types of shell concentrations can be distinguished that differ from each other in a number of ecological and taphonomic features, such as species diversity, preservation quality, orientation in cross-section, percentage of disarticulation, and degree of biogenic alteration. Characteristic features of concentrations at the base of the TSTs are moderate time-averaging, sorting, a preferred convex-up orientation, and nearly total disarticulation of shells. They are suggestive of an environment in which reworking and local transport were frequent events. Similar features are shown by concentrations near the tops of the HSTs, except that there shells were largely concentrated in lenses and in pavements rather than in beds as in the transgressive lags. Associated sedimentary structures indicate deposition above fair weather wave base in a high-energy environment. Concentrations occurring in the MFZ, in contrast, are autochthonous and highly time-averaged, having accumulated during times of low rates of sedimentation below storm wave base. This is supported by their high preservation quality (comparatively high percentage of articulated shells, shells of infaunal organisms commonly preserved in life position), biogenic alteration being the most important taphonomic agent. The dominant elements of these shell concentrations, i.e. Seebachia, Megacuccullaea, and Indotrigonia in the Upper Jurassic, and Pisotrigonia in the Lower Cretaceous, are endemic to the Ethiopean faunal province and belong to lineages that rapidly evolved during this time period.

Toarcian (Lower Jurassic) argillaceous-marly sediments of southern France (Causses) and east-central Spain (Barranco de la Puta section) were deposited in mid to lower shelf settings. They contain a low to moderately diverse, autochthonous fauna of benthic macroinvertebrates dominated by bivalves and gastropods, in the case of the Causses, and by bivalves and brachiopods in the Barranco de la Puta section. Five benthic associations are recognized at the latter locality and four at the former. In the Causses, low species diversity, evidence of seasonal mass mortality, presence of the opportunistic bivalve Parvamussium pumilum, local dominance of the soft bottom coral Thecocyathus mactrus and the dark-grey, fine-grained sediment point to high rates of sedimentation, high turbidity, intermittently lowered oxygen values and soft to soupy substrate conditions. These factors, together with eutrophic water masses, were the main environmental parameters governing faunal distribution. Soupy substrate conditions are thought to be largely biologically produced by the activity of infaunal depositfeeders, chiefly nuculoid bivalves. In the Barranco de la Puta section, abundant brachiopods, higher carbonate content of the sediment, and evidence of intermittent in-situ reworking and winnowing point to an influence of storm-induced currents, a shallower depositional depth, lower turbidity, a lower rate of sedimentation, and a somewhat firmer substrate. As a consequence, the fauna is largely dominated by epifaunal suspension-feeders. Compared with maximum and average sizes from elsewhere in the Jurassic, most bivalve species are distinctly smaller, a feature interpreted as stunting. Brachiopods, in contrast, reach normal size. The lack of nuculids, scarcity of deposit-feeders in general, and stunting are interpreted as evidence of an oligotrophic environment. Lowered oxygen conditions appear to have played only a very limited role in shaping the distribution pattern. Many of the differences between both areas can be explained by the different trophic regimes that reflect considerably higher run-off and consequently higher input of terrigenous sediment and dissolved nutrients to the basin in the case of the Causses. This in turn is thought to possibly reflect differences in regional climate; humid in southern France and more arid in eastcentral Spain.

Using multivariate methods, the distribution pattern of Jurassic bivalve genera and subgenera within the Proto-Atlantic and along the southern margin of the Tethys is analysed based on an extensive literature survey and examination of field collections. Four bivalve provinces are recognised within the Proto-Atlantic: (1) the Boreal Bivalve Province in the north; (2) the Northern Transitional Province; (3) the Southern Transitional Province; and (4) the Mediterranean Bivalve Province. The former two provinces are assigned to the Boreal Faunal Realm, the latter two to the Tethyan Faunal Realm. The southwestern margin of the Tethys belongs to the Mediterranean Bivalve Province, the southeastern margin to the Ethiopian Bivalve Province. The latter is only poorly defined by bivalve genera/subgenera; in particular, its northern boundary is blurred, with the Arabian region occupying an intermediate position between the Mediterranean and the Ethiopian bivalve provinces. Province boundaries based on bivalves do not always coincide with those based on ammonites. The reason for this is probably different modes of life: ammonites, as a rule, being active swimmers and bivalves being substrate-related and subjected to passive dispersal during the larval stage. Diversity is not suitable to characterize bivalve provinces, due to differences in outcrop size, preservation potential and sampling history, and due to differences in the degree of environmental heterogeneity within and between regions. Migration patterns of Jurassic bivalves either reflect changes in the climatic condition (e.g. the northward spread of Tethyan taxa in the late Early Jurassic and Middle Jurassic in the course of amelioration of the climate) or prevailing current patterns. The origin of faunal provinciality is thought to be complex and a result of the interplay of several factors, the importance of which varied throughout the Jurassic.

Lower Bathonian sediments of the Causses, southern France, largely represent very shallow low energy carbonates deposited on an extensive carbonate platform. Environments range from distal oolite shoals to shallow lagoons, interto supratidal mudflats, brackish bays, coastal swamps and freshwater ponds. Associated benthic macrofauna occurs often in high abundance, but low diversity and is dominated by bivalves and gastropods. Stenohaline elements are rare to absent. The fauna can be grouped in 13 associations, some of them monospecific, and several assemblages. Some of the associations are clearly substrate-controlled, especially by grain size and substrate consistency. However, the main controlling factor appears to have been salinity which fluctuated from zero (freshwater) to more than 40‰ (hypersaline). An analysis integrating sedimentological data, microfauna, microflora, and ecological data of the macrobenthos made it possible to assign the benthic associations to various salinity regimes. Accordingly, the Naricopsina matheroni association is restricted to freshwater; the Eomiodon angulatus, Myrene raristriata, Neomiodon ruthenensis, and Neomiodon ruthenensis-Placunopsis socialis associations occupied the oligohaline-mesohaline regimes; the Placunopsis socialis association ranged from the upper mesohaline to the lower brachyhaline regime; the Protocardia stricklandi, Protocardia buckmani-“Ostrea” sp., Protocardia buckmani, Bakevellia waltoni, and Bakevellia waltoni-Protocardia buckmani associations lived in brachyhaline environments. Only two associations, the Pholadomya lirata and the Ceratomya striata associations, occurred in normal marine water. The opportunistic Myrene raristriata apparently managed to thrive also in hypersaline environments as is shown by its close association with pseudomorphs after autigenic gypsum and with algal layers. The Lower Bathonian macrofauna of southern France resembles that of other Middle Jurassic salinity-controlled benthic faunas from Scotland, Northern Africa, Western India, and Tibet except for its scarcity of mytilid bivalves and lack of corbulids.

Salinity-controlled benthic macroinvertebrate associations are typical of many Mesozoic marginally marine environments. They can be recognized by abiotic criteria (e.g., environmental setting, specific autigenic minerals), by biotic criteria (faunal composition, diversity, shell morphology, size-frequency histograms, taphonomic features, associated micro fauna and microflora), and by isotope geochemistry of shells. Although salinity-controlled associations must have been widespread in the European German Triassic, very little is known about their ecology. They appear to have been dominated by the bivalve Unionites and the brachiopod Lingula. In the Jurassic, brackish-water associations are characterized by bivalves, in particular neomiodontids, corbulids, mytilids, bakevelliids, isognomonids, and oysters. In the Cretaceous, in addition, corbiculid bivalves and gastropods become increasingly abundant. Salinity-controlled benthic macroinvertebrate associations can be used to reconstruct salinity regimes of ancient environments, but emphasis should be placed on an integrated sedimentological and ecological approach, as salinity is rarely the only parameter influencing faunal composition and diversity. Although the species composition of salinity-controlled benthic associations changes distinctly through time, the composition of morphotypes remains surprisingly constant throughout the Mesozoic and up to the Recent, evidence of a conservative evolution of benthic faunas within marginal marine high-stress environments. □Salinity, benthic associations, palaeoecology, Mesozoic.

Upper Callovian to Oxfordian shelf sediments at Ler in the Kachchh Basin, western India, are interpreted in terms of transgressive-regressive cycles. The transgressive phases are represented by thin layers of reworked and bored concretions, sometimes in association with skeletal concentrations, the regressive phases are documented by much thicker units of largely fine-grained sediments. The benthic fauna of transgressive and regressive phases differes markedly and thus mirrors the sedimentary cycles: During transgressive phases non-sedimentation produced hard substrates colonized mainly by byssate, cemented, or pedicle-attached suspension-feeding epifaunal species, whilst sediment input during regressive phases lead to soft substrate conditions characterized by infaunal deposit- and suspension-feeders as well as by epifaunal opportunists. Whereas the composition of the “regressive fauna” remains fairly constant through time, that of successive “transgressive faunas” often differs drastically. This is possibly due to a greater environmental sensitivity of epifaunal taxa as compared to infaunal taxa.

The sediments forming the Cassian Formation (Middle—Upper Triassic) of the Central Dolomites represent the following environments: back-reef areas, shallow marginal basins, slope, and central basin. In each of these major environments faunal assemblages were found whose composition, mode of preservation and occurrence proved to be characteristics. In the back-reef areas, algal/foraminifera- and calcareous sponge/coral-patch reefs with a highly diverse fauna of frame-builders and reef-dwellers, in some localities excellently preserved, form the most conspicuous feature. In the shallow marginal basins autochthonous algal meadow/soft-bottom associations dominated by gastropods and deposit-feeding bivalves prevail. Slope deposits do not contain any autochthonous associations but either remains of pelagic faunas or transported faunal elements of shallow-water origin in the form of Cipit boulders (subaerially cemented parts from the outer edge of the carbonate platforms), worn Pachycardia rugosa-dominated, or echinoderm debris-dominated assemblages. Sediments of the central basin lack benthic faunas but contains pelagic assemblages of low diversity dominated by Daonella, Posidonia, and some ammonites.

Excellently preserved specimens of the trace fossil Haenrzschelinia onoi (Geinitz) allow its three-dimensional reconstruction and interpretation of the behaviour underlying the morphological pattern. H. onoi is a rosette-shaped endogenic trace fossil comprising central tube and branching incomplete radial protrusive spreiten. The basic behaviour pattern (rosetted vertical spreiten with central shaft) is the same as that of Brooksella Walcott 1896 and Dactyloidites Hall 1886. Haentzschelinia is therefore placed in synonymy with Dactyloidites, which has priority.

Several of the seventeen macroinvertebrate associations found in the Corallian (Middle and Upper Oxfordian) of England and Normandy show preferences for particular environments whereas other, consisting mainly of epifaunal organisms, display a high degree of independence. Because different associations seem to have been able to live in similar environments and similar associations in different environments, the macroinvertebrate fauna is not a very useful tool in interpreting bathymetry, except if all other available evidence (e.g., sedimentary structures, trace fossils) is taken into account as well. Most of the transgressive horizons observed in southern England and postulated to have been fairly widespread, could also be found in Normandy.

OMonotypic and very low diversity virgianid shell beds from the Upper Ordovician to Lower Silurian dolomites of North Greenland were formed in marginal marine quiet-water hypersaline environments. In the light of this evidence the salinity tolerances of other Palaeozoic articulate brachiopods is evaluated. There are only a small number of species apparently invading hypersaline or brackish environments, but it is significant considering that previously all articulate brachiopods were thought to be fully marine. Two types of occurrence are noted, those species specifically related to marginally marine environments, disappearing with the introduction of fully marine faunas, and the majority of species which extend their normal marine range into marginal conditions. No brachiopod species appears to have invaded very hypersaline or truly brackish conditions. No single group of articulate brachiopods specifically specialised in colonising marginal marine environments, apart from possibly the virgianid pentamerids. Palaeozoic, Upper Ordovician, Lower Silurian, Brachiopoda. Pentamerida, Virgianidae, Greenland, palaeoecology. hypersaline environments, brackish environments.

The distribution of trace fossils in Corallian (Upper Jurassic) rocks has been studied in three coastal areas in Yorkshire, Dorset, and Normandy. Three trace fossil associations, primarily related to the hydrodynamic conditions and only indirectly to depth, can be distinguished: the high-energy Diplocraterion association, and the low-energy Rhizocorallium and Teichichnus associations. The characteristic members of these associations can be used as environmental indicators throughout the Jurassic.

The Upper Jurassic of Milne Land, Greenland, is a transgressive-regressive sequence ranging from offshore shallow sandbar complexes in the Late Oxfordian to outer shelf muds in the Kimmeridgian and Early to Middle Volgian. Within the Middle Volgian rapid shoreline progradation led to deposition of inner-shelf silts and nearshore sands. Within this envirobmental framework 22 benthic macroinvertebrate associations and several assemblages occur. They are dominated by suspension-feeding bivalves, less commonly by brachiopods or detritus-feeding serpulid polychaetes. Despite frequently low rates of sedimentation and plenty of suitable substrates, surprisingly few shells are bored or encrusted, which may reflect biogeographic factors. Although some inter- and intraspecific interactions are recorded, the associations are thought to have been largely controlled by environmental parameters. Low-diversity associations are related to low oxygen conditions at the sea floor or unstable, shifting substrates, but in some cases may have been due to biotic interactions. Levels with reduced rates of sedimentation and glauconite formation are characterized by epifaunal associations, those with higher rates of sedimentation by infaunal or semi-infaunal associations. The temporal and spatial distribution pattern of the benthic invertebrate fauna is fairly complex due to the interplay of several biotic and abiotic factors, the absence of strong environmental gradients in outer-shelf areas, and diagenetic overprint selectivity removing low-density faunas. Among bivalves, species replacement through time was, in most cases, ecological.

The Upper Kimmeridgian—basal Tithonian clastic sequence at Santa Cruz, Estremadura, represents environments ranging from river channels and flood plains to lagoons and protected bays showing a deltaic influence. Within the marginal marine environments, five benthic macroinvertebrate associations are recognized and analysed in terms of diversity and species composition. All five are thought to be controlled largely by salinity and to represent lowered and/or fluctuating salinity regimes. They can be grouped along a salinity gradient in which the Mesosaccella dammariensis—Corbulomima suprajurensis association, occurring in prodelta silts and marls, represents the closest approach to fully marine conditions and in which the Eomiodon securiformis association, typical of delta front sands, extends into the oligohaline regime. Banks of the Isognomon lusitanicum association and patch reefs of the Praeexogyra pustulosa—Nanogyra nana association are thought to be typical of brachy-to mesohaline conditions occurring in brackish bays and lagoons. Characteristic of the latter salinity regimes is also the Jurassicorbula edwardi association. The integrated approach, using benthic faunas, trace fossils and sedimentological data, leads to a detailed interpretation of the sedimentary sequences and the construction of a biofacies model which can also be used for other parts of the Lusitanian Basin.

The macroinvertebrate fauna of the Corallian (Middle and Upper Oxfordian) often exhibits a clear relationship to ten types of substrates ranging from clays to oolites. Whereas diversity and abundance of infauna decreases with increasing grain size, abundance of epifauna increases. Suspension-feeders dominate the ecological spectrum in all types of substrates, except for silts, where deposit-feeders abound. These results have been compared to data from other horizons in the Jurassic and to observations in the Recent.

Shell beds in a Cretaceous lagoonal fill resulted from a combination of low sediment input, high organic productivity, and reworking by storm processes. The skeletal concentrations occur in a shelly shale unit 2-3 m thick in the upper sandstone member (Late Cenomanian) of the Dakota Formation of northeastern Arizona. The shell beds are parautochthonous relics of a former brackish-water community dominated by the infaunal suspension-feeding bivalve Caryocorbula ovisana. Analysis of 74 samples and more than 12,000 specimens allows subdivision of this association into four subsets characterized by the bivalves Flemingostrea prudentia/Anomia ponticulana, Brachidontes filisculptus, and corbulid sp. A, and the gastropod Voysa sp. Biostratinomic, sedimentologic, and paleoecologic data allow reconstruction of a stratified brackish-water lagoon system. Saline, low-oxygen waters below storm wave base occurred at least locally in deeper parts of the lagoon system and were characterized by a monospecific assemblage of lucinid bivalves. The low-oxygen water was overlain by brachyhaline waters that were below fairweather wave base, but were within the reach of storms. This habitat supported a moderately diverse fauna of benthic molluscs. The lagoon was capped by water of strongly reduced salinity (mesohaline regime) and contained a very low diversity fauna. Progradation of the low-energy lagoonal shore resulted in the establishment of nonmarine environments in some parts of the lagoon. This sequence is overlain by reworked barrier-bar sands deposited during the ensuing transgression

Densely fossiliferous deposits are receiving increasing attention for their yield of paleobiologic data and their usefulness in sedimentology and stratigraphy. This trend has created a pressing need for standardized descriptive terminology and a genetic classification based on a coherent conceptual framework. The descriptive procedure outlined here for skeletal concentrations stresses four features -taxonomic composition, bioclastic fabric, geometry, and internal structure-that can be described readily in the field by nonspecialists. The genetic classification scheme is based on three end members, representing biologic, sedimentologic, and diagenetic factors in skeletal concentration. Concentrations created through the simultaneous or sequential action of two or more factors are classified as mixed types. As a conceptual framework for comparative biostratinomic analysis, the broad categories of this ternary classification scheme should facilitate recognition of large-scale temporal and spatial patterns in skeletal accumulation. The usefulness of this approach is suggested by the good agreement between biostratinomic patterns observed in ancient onshore-offshore facies tracts and those predicted across paleobathymetric transects based on modern processes of skeletal concentration.