First gut contents in a Cretaceous sea turtle

Modern sea turtles utilize a variety of feeding strategies ranging from herbivory to omnivory. In contrast, the diets of fossil sea turtles are poorly known. This study reports the first direct evidence: inoceramid bivalve shell pieces (encased in phosphatic material) preserved within the body cavities of several small protostegid turtles (cf. Notochelone) from the Lower Cretaceous of Australia. The shell fragments are densely packed and approximately 5-20 mm across. Identical shell accumulations have been found within coprolite masses from the same deposits; these are of a correct size to have originated from Notochelone, and indicate that benthic molluscs were regular food items. The thin, flexible inoceramid shells (composed of organic material integrated into a prismatic calcite framework) appear to have been bitten into segments and ingested, presumably in conjunction with visceral/mantle tissues and encrusting organisms. Although protostegids have been elsewhere interpreted as potential molluscivores, their primitive limb morphology is thought to have limited them to surface feeding. However, the evidence here that at least some forms were able to utilize benthic invertebrate prey indicates that, like modern sea turtles, protostegids probably exhibited a much broader range of feeding habits.     

Veligers from the nudibranch <Emphasis Type="Italic">Dendronotus</Emphasis><Emphasis Type="Italic">frondosus</Emphasis> show shell growth and extended planktonic period in laboratory culture

The planktonic period of planktotrophic veliger larvae from the nudibranch Dendronotus frondosus was characterized by laboratory culture methods. Larvae in culture successfully metamorphosed at 73–86 days after hatching. These veligers have Type 2 (Thompson) larval shells that significantly increased in length over the first 7–14 days after hatching. Direct observations of the development of nudibranch larvae with Type 2 protoconchs are limited, and these data help clarify previous attempts to correlate shell type and growth with minimum planktonic periods. Although these are not absolute values for the planktonic period of D. frondosus larvae, these data show the potential for extended larval dispersal and may help explain reports of an extensive geographic range in north-temperate waters for this species.     

Larval ecology and morphology in fossil gastropods

The shell of marine gastropods conserves and reflects early ontogeny, including embryonic and larval stages, to a high degree when compared with other marine invertebrates. Planktotrophic larval development is indicated by a small embryonic shell (size is also related to systematic placement) with little yolk followed by a multiwhorled shell formed by a free‐swimming veliger larva. Basal gastropod clades (e.g. Vetigastropoda) lack planktotrophic larval development. The great majority of Late Palaeozoic and Mesozoic ‘derived’ marine gastropods (Neritimorpha, Caenogastropoda and Heterobranchia) with known protoconch had planktotrophic larval development. Dimensions of internal moulds of protoconchs suggest that planktotrophic larval development was largely absent in the Cambrian and evolved at the Cambrian–Ordovician transition, mainly due to increasing benthic predation. The evolution of planktotrophic larval development offered advantages and opportunities such as more effective dispersal, enhanced gene flow between populations and prevention of inbreeding. Early gastropod larval shells were openly coiled and weakly sculptured. During the Mid‐ and Late Palaeozoic, modern tightly coiled larval shells (commonly with strong sculpture) evolved due to increasing predation pressure in the plankton. The presence of numerous Late Palaeozoic and Triassic gastropod species with planktotrophic larval development suggests sufficient primary production although direct evidence for phytoplankton is scarce in this period. Contrary to previous suggestions, it seems unlikely that the end‐Permian mass extinction selected against species with planktotrophic larval development. The molluscan classes with highest species diversity (Gastropoda and Bivalvia) are those which may have planktotrophic larval development. Extremely high diversity in such groups as Caenogastropoda or eulamellibranch bivalves is the result of high phylogenetic activity and is associated with the presence of planktotrophic veliger larvae in many members of these groups, although causality has not been shown yet. A new gastropod species and genus, Anachronistella peterwagneri, is described from the Late Triassic Cassian Formation; it is the first known Triassic gastropod with an openly coiled larval shell.     

Genetic diversity and gene flow in collapsed and healthy abalone fisheries

Overexploitation of marine species invariably results in population decline but can also have indirect effects on ecological processes such as larval dispersal and recruitment that ultimately affect genetic diversity and population resilience. We compared microsatellite DNA variation among depleted and healthy populations of the black-lip abalone Haliotis rubra from Tasmania, Australia, to determine if over-fishing had affected genetic diversity. We also used genetic data to assess whether variation in the scale and frequency of larval dispersal was linked to greater population decline in some regions than in others, and if larval dispersal was sufficient to facilitate natural recovery of depleted populations. Surprisingly, allelic diversity was higher in depleted populations than in healthy populations ( P <  0.05). Significant subdivision across hundreds of metres among our sampling sites ( F _ST = 0.026, P  < 0.01), coupled with assignment tests, indicated that larval dispersal is restricted in all regions studied, and that abalone populations across Tasmania are largely self-recruiting. Low levels of larval exchange appear to occur at the meso-scale (7–20 km), but age estimates based on shell size indicated that successful migration of larvae between any two sites may happen only once every few years. We suggest that genetic diversity may be higher in depleted populations due to the higher relative ratio of migrant to self-recruiting larvae. In addition, we expect that recovery of depleted abalone populations will be reliant on sources of larvae at the meso-scale (tens of km), but that natural recovery is only likely to occur on a timescale unacceptable to fishers and resource managers.     

The Paleozoic evolution of the gastropod larval shell: larval armor and tight coiling as a result of predation‐driven heterochronic character displacement

Early and middle Paleozoic gastropod protoconchs generally differ strongly from their corresponding adult morphologies, that is, most known protoconchs are smooth and openly coiled, whereas the majority of adult shells are ornamented and tightly coiled. In contrast, larval and adult shells of late Paleozoic gastropods with planktotrophic larval development (Caenogastropoda, Neritimorpha) commonly resemble each other in shape and principle ornamentation. This is surprising because habitat and mode of life of planktonic larvae and benthic adults differ strongly from each other. Generally, late Paleozoic to Recent protoconchs are tightly coiled. This modern type of larval shell resembles the adult shell morphology and was obviously predisplaced onto the larval stage during the middle Paleozoic. The oldest known planktonic‐armored (strongly ornamented) larval shells are known from the late Paleozoic. However, smooth larval shells are also common among the studied late Paleozoic gastropods. The appearance of larval armor at the beginning of the late Paleozoic could reflect an increase of predation pressure in the plankton. Although there are counter examples in which larval and adult shell morphology differ strongly from each other, there is statistical evidence for a heterochronic predisplacement of adult characters onto the larval stage. Larval and adult shells are built in the same way, by accretionary secretion at the mantle edge. It is likely that the same underlying gene expression is responsible for that. If so, similarities of larval and adult shell may be explained by gene sharing, whereas differences may be due to different (planktic vs. benthic life) epigenetic patterns.     

The brachiopod <Emphasis Type="Italic">Eoobolus</Emphasis> from the Early Cambrian Mural Formation (Canadian Rocky Mountains)

The Early Cambrian brachiopod, Eoobolus, is one of the first representatives of the superfamily, Linguloidea, the defining characteristics of which include the classical morphology of oval shells and a pedicle that emerges from between the two valves. The material described here from the Mural Formation (Jasper National Park, Canadian Rocky Mountains) provides well-preserved muscle scars and larval shells that allow a discussion of the muscle system and the larval morphology of Eoobolus. The dorsal larval shell exhibits a morphology similar to other Cambrian linguloids, but also to paterinids, Mickwitzia muralensis, and some rhynchonelliforms. This suggests that there was a lesser degree of disparity among brachiopod larvae in the Cambrian than there is today. The muscle system of Eoobolus is similar to other linguloids, but differs from that of Recent lingulids and discinids by having one or two more pairs of oblique muscles. New data on the distribution of features characteristic of the family Eoobolidae question the validity of this family.     

Description of the early ontogenic part of the Tentaculitids, with implications for classification

Ontogenic development and classification of tentaculitids at high systematic levels are reevaluated in the light of new findings on shell structure and morphology of larval parts, and these features are here regarded as being of primary importance for taxonomy. Class Tentaculita Bouček, 1964 is subdivided into two subclasses, of which subclass Chionioconarida Farsan, 1994 is distinguished by a tubular larval process closed at the apex and covered with microrings. The process is differentiated into a prolarval, metalarval and epilarval part, of which the latter coincides with metamorphosis. Morphology of the larval parts suggests that metamorphosis proceeds in two different manners, giving rise to superorders within this subclass. Within superorder Trompetoconarida Farsan, 1994 a bilaterally symmetrical larval cone develops with an aperture oblique to the long axis of the conch; following metamorphosis the conch becomes radially symmetrical and the aperture perpendicular to the axis; secondary shell, septa and pseudopunctae develop in the adult phase, and the structure of the shell is lamellar. In contrast, within the second superorder, Lirioconarida Farsan, 1994 the epilarval tube develops into a larval bulb with no changes in symmetry and position of the aperture; secondary shell, septa and pseudopuncta are absent. The microstructure of the shell is lamellar in the larval part whereas in postlarval parts it is either sigmoidal or lamellar. The subclass Dacryoconarida Fisher, 1962 possesses a subspherical, tear- or drop-like embryonic chamber which may have a caudal process. The microstructure of the embryonic chamber is variable within this group, being lamellar in some taxa whereas in others, a single layer of shell is present. The postembryonic parts of the lamellar forms possess nacreous or sigmoidal structures.     

Large‐scale,multidirectional larval connectivity among coral reef fish populations in the Great Barrier Reef Marine Park

Larval dispersal is the key process by which populations of most marine fishes and invertebrates are connected and replenished. Advances in larval tagging and genetics have enhanced our capacity to track larval dispersal, assess scales of population connectivity, and quantify larval exchange among no‐take marine reserves and fished areas. Recent studies have found that reserves can be a significant source of recruits for populations up to 40 km away, but the scale and direction of larval connectivity across larger seascapes remain unknown. Here, we apply genetic parentage analysis to investigate larval dispersal patterns for two exploited coral reef groupers (Plectropomus maculatus and Plectropomus leopardus) within and among three clusters of reefs separated by 60–220 km within the Great Barrier Reef Marine Park, Australia. A total of 69 juvenile P. maculatus and 17 juvenile P. leopardus (representing 6% and 9% of the total juveniles sampled, respectively) were genetically assigned to parent individuals on reefs within the study area. We identified both short‐distance larval dispersal within regions (200 m to 50 km) and long‐distance, multidirectional dispersal of up to ~250 km among regions. Dispersal strength declined significantly with distance, with best‐fit dispersal kernels estimating median dispersal distances of ~110 km for P. maculatus and ~190 km for P. leopardus. Larval exchange among reefs demonstrates that established reserves form a highly connected network and contribute larvae for the replenishment of fished reefs at multiple spatial scales. Our findings highlight the potential for long‐distance dispersal in an important group of reef fishes, and provide further evidence that effectively protected reserves can yield recruitment and sustainability benefits for exploited fish populations.     

Population structure is not a simple function of reproductive mode and larval type: insights from tropical corals

1. For a wide range of organisms, heritable variation in life-history characteristics has been shown to be strongly subject to selection, reflecting the impact that variation in characters such as genotypic diversity, duration of larval development and adaptations for dispersal can have on the fitness of offspring and the make-up of populations. Indeed, variation in life-history characteristics, especially reproduction and larval type, have often been used to predict patterns of dispersal and resultant population structures in marine invertebrates. 2. Scleractinian corals are excellent models with which to test this relationship, as they exhibit almost every possible combination of reproductive mode and larval type. Some general patterns are emerging but, contrary to expectations, genetic data suggest that while populations of broadcast spawning species may be genotypically diverse they may be heavily reliant on localized recruitment rather than widespread dispersal of larvae. 3. Here we use microsatellites to test the importance of localized recruitment by comparing the genetic structure of populations of two broadcast spawning corals with contrasting modes of reproduction and larval development; Goniastrea favulus is self-compatible, has sticky, negatively buoyant eggs and larvae and is expected to have restricted dispersal of gametes and larvae. In contrast, Platygyra daedalea is self-incompatibile, spawns positively buoyant egg-sperm bundles and has planktonic development. 4. Surprisingly, spatial-autocorrelation revealed no fine-scale clustering of similar genotypes within sites for G. favulus, but showed a non-random distribution of genotypes in P. daedalea. Both species showed similar levels of genetic subdivision among sites separated by 50-100 m (F(ST) = 0.03), suggesting that larval dispersal may be equivalent in both species. 5. Interestingly, as fragmentation has been considered rare in massive corals, our sample of 284 P. daedalea colonies included 28 replicated genotypes that were each unlikely (P < 0.05) to have been derived independently from sexual reproduction. 6. We conclude that the extreme life history of G. favulus does not produce unusually fine-scale genetic structure and subsequently, that reproductive mode and larval type may not be not good predictors of population structure or dispersal ability.     

Role of larval host plants in the climate-driven range expansion of the butterfly Polygonia c-album

1. Some species have expanded their ranges during recent climate warming and the availability of breeding habitat and species' dispersal ability are two important factors determining expansions. The exploitation of a wide range of larval host plants should increase an herbivorous insect species' ability to track climate by increasing habitat availability. Therefore we investigated whether the performance of a species on different host plants changed towards its range boundary, and under warmer temperatures. 2. We studied the polyphagous butterfly Polygonia c-album, which is currently expanding its range in Britain and apparently has altered its host plant preference from Humulus lupulus to include other hosts (particularly Ulmus glabra and Urtica dioica). We investigated insect performance (development time, larval growth rate, adult size, survival) and adult flight morphology on these host plants under four rearing temperatures (18-28.5 degrees C) in populations from core and range margin sites. 3. In general, differences between core and margin populations were small compared with effects of rearing temperature and host plant. In terms of insect performance, host plants were generally ranked U. glabra > or = U. dioica > H. lupulus at all temperatures. Adult P. c-album can either enter diapause or develop directly and higher temperatures resulted in more directly developing adults, but lower survival rates (particularly on the original host H. lupulus) and smaller adult size. 4. Adult flight morphology of wild-caught individuals from range margin populations appeared to be related to increased dispersal potential relative to core populations. However, there was no difference in laboratory reared individuals, and conflicting results were obtained for different measures of flight morphology in relation to larval host plant and temperature effects, making conclusions about dispersal potential difficult. 5. Current range expansion of P. c-album is associated with the exploitation of more widespread host plants on which performance is improved. This study demonstrates how polyphagy may enhance the ability of species to track climate change. Our findings suggest that observed differences in climate-driven range shifts of generalist vs. specialist species may increase in the future and are likely to lead to greatly altered community composition.     

Biomechanics of Larval Morphology Affect Swimming: Insights from the Sand Dollars Dendraster excentricus

Most planktonic larvae of marine invertebrates are denser than sea water, and rely on swimming to locate food, navigate advective currents, and avoid predators. Therefore, swimming behaviors play important roles in larval survival and dispersal. Larval bodies are often complex and highly variable across developmental stages and environmental conditions. These complex morphologies reflect compromises among multiple evolutionary pressures, including maintaining the ability to swim. Here, I highlight metrics of swimming performance, their relationships with morphology, and the roles of behavior in modulating larval swimming within biomechanical limits. Sand dollars have a representative larval morphology using long ciliated projections for swimming and feeding. Observed larval sand dollars fell within a narrow range of key morphological parameters that maximized their abilities to maintain directed upward movement over the most diverse flow fields, outperforming hypothetical alternatives in a numerical model. Ontogenetic changes in larval morphology also led to different vertical movements in simulated flow fields, implying stage-dependent vertical distributions and lateral transport. These model outcomes suggest a tight coupling between larval morphology and swimming. Environmental stressors, such as changes in temperature and pH, can therefore affect larval swimming through short-term behavioral adjustments and long-term changes in morphology. Larval sand dollars reared under elevated pCO(2) conditions had significantly different morphology, but not swimming speeds or trajectories. Geometric morphometric analysis showed a pH-dependent, size-mediated change in shape, suggesting a coordinated morphological adjustment to maintain swimming performance under acidified conditions. Quantification of the biomechanics and behavioral aspects of swimming improves predictions of larval survival and dispersal under present-day and future environmental conditions.     

Role of dispersal ability in the phenotypic differentiation and plasticity of two marine gastropods

Species with contrasting abilities for dispersal may adopt different strategies in response to wide ranges of environmental conditions. These strategies were investigated here by comparisons of phenotypic differentiation and plasticity in the gastropods Austrocochlea constricta and Bembicium vittatum, which coexist in a range of intertidal habitats on the Abrolhos Islands and Albany in Western Australia. They differ in their potential for larval dispersal, A. constricta having a short mobile planktonic stage and B. vittatum developing directly from benthic eggs. Levels of among-population variation in shell shape and maximum size did not differ between the species, or between locations subject to contrasting levels of gene flow in the case of A. constricta. Results of a common garden translocation experiment, coupled with those of previous breeding experiments, suggest that variation in shape is predominantly genetically determined in B. vittatum, but plastic in A. constricta. Plasticity of shape in A. constricta was most pronounced at Albany, where previous data suggested the widest gene flow, and was greater than in B. vittatum at both locations. Change of shape in A. constricta subsequent to translocation was related to growth rate, a trait which was also more plastic in this species than in B. vittatum. The results agree with the notion that wide dispersal enhances physiological flexibility, while restricted dispersal promotes local genetic adaptation, but disagree with the hypothesis that wide dispersal promotes phenotypic homogeneity. Received: 31 May 1996 / Accepted: 30 September 1996     

Relative larval loss among females during dispersal of Lake Sturgeon (<Emphasis Type="Italic">Acipenser fulvescens</Emphasis>)

Mortality that occurs during larval dispersal as a consequence of environmental, maternal, and genetic effects and their interactions can affect annual recruitment in fish populations. We studied larval lake sturgeon (Acipenser fulvescens) drift for two consecutive nights to examine whether larvae from different females exposed to the same environmental conditions during dispersal differed in relative levels of mortality. We estimated proportional contributions of females to larval collections and relative larval loss among females as larvae dispersed downstream between two sampling sites based on genetically determined parentage. Larval collections were composed of unequal proportions of offspring from different females that spawned at upstream and downstream locations (~0.8 km apart). Hourly dispersal patterns of larvae produced from females spawning at both locations were similar, with the largest number of larvae observed during 22:00–23:00 h. Estimated relative larval loss did not differ significantly among females as larvae were sampled at two sites approximately 0.15 and 1.5 km from the last section downstream of spawning locations. High inter- and intra-female variation in larval contributions and relative larval loss between nights may be a common feature of lake sturgeon and other migratory fish species, and likely is a source of inter-annual and intra-annual variation in fish recruitment.     

The presence of Tawera gayi (Hupé in Gay, 1854) (Veneridae, Bivalvia) in southern South America: Did Tawera achieve a Late Cenozoic circumpolar traverse?

Cenozoic Tawera Marwick, 1927 from the Southern Hemisphere exhibits a pattern of disjunt distribution around the southern oceans. A single species, Tawera gayi (Hupé in [Gay, C. (1854). Historia Física y Política de Chile, Zoología 8. Paris.]) is confined to southern South America. Taking into account the occurrence of Tawera in the fossil record, taxonomy based on shell morphology, and available information on extant species of Tawera, it is plausible that the genus appeared first in southern Australia during the Early Miocene, and then expanded and radiated to New Zealand. It also appears that Tawera first crossed from Australasia to South America during the Early Pleistocene. This picture can be better explained if Tawera was able to achieve circumglobal range by means of the Antarctic Circumpolar Current. Thus, different potential factors of dispersal (i.e., larval dispersal, drifting, kelp rafting and Pleistocene cooling) are considered and discussed.

Shell morphology and overall appearance of Tawera gayi is very similar to Tawera philomela (Smith, 1885) from South Africa and Tawera mawsoni (Hedley, 1916) from Macquarie Island, suggesting these taxa have a close relationship. One postulated explanation, which should be confirmed by means of a phylogenetic study, is a subsequent migration of Tawera from South America arriving first to the Southern African Region (via the West Wind Drift Islands Province), and then probably coming back again to Australasia. It could have been mediated via the same current during the Late Pleistocene and much later during the Holocene.     

Predicting dispersal of auto‐gyrating fruit in tropical trees: a case study from the Dipterocarpaceae

Seed dispersal governs the distribution of plant propagules in the landscape and hence forms the template on which density‐dependent processes act. Dispersal is therefore a vital component of many species coexistence and forest dynamics models and is of applied value in understanding forest regeneration. Research on the processes that facilitate forest regeneration and restoration is given further weight in the context of widespread loss and degradation of tropical forests, and provides impetus to improve estimates of seed dispersal for tropical forest trees. South‐East Asian lowland rainforests, which have been subject to severe degradation, are dominated by trees of the Dipterocarpaceae family which constitute over 40% of forest biomass. Dipterocarp dispersal is generally considered to be poor given their large, gyration‐dispersed fruits. However, there is wide variability in fruit size and morphology which we hypothesize mechanistically underpins dispersal potential through the lift provided to seeds mediated by the wings. We explored experimentally how the ratio of fruit wing area to mass (“inverse wing loading,” IWL) explains variation in seed dispersal kernels among 13 dipterocarp species by releasing fruit from a canopy tower. Horizontal seed dispersal distances increased with IWL, especially at high wind speeds. Seed dispersal of all species was predominantly local, with 90% of seed dispersing <10 m, although maximum dispersal distances varied widely among species. We present a generic seed dispersal model for dipterocarps based on attributes of seed morphology and provide modeled seed dispersal kernels for all dipterocarp species with IWLs of 1–50, representing 75% of species in Borneo.     

The cnidome and ultrastructural morphology of late planulae in Lophelia pertusa (Linnaeus, 1758)—With implications for settling competency

The larval pre-competency period and competency window are important in delimiting the potential dispersal distance for pelagic larvae of sessile marine fauna. Here, we provide evidence for morphological changes in the late planulae of Lophelia pertusa that have implications for their dispersal potential. Three weeks after spawning, the planulae gain functional cnidocysts, indicating that they are competent to settle at this time. Cnidae have been shown to be used for primary anchoring during settling, and before this time point, the larvae most probably do not have the ability to attach to a substrate in high flow conditions. The appearance of functional cnidae coincides with larvae gaining a flexible mouth that can be opened to the full width of the larva. The larval isorhizas differ the most from the adult polyps isorhizas, while the p- and b-mastigophores bear more resemblance to the adult homologues of similar size. The external and internal morphology of late planulae is further described with demonstration of long apical cilia and its effect on swimming agility, morphological changes of the ciliated cells in the larval mouth region and an internal nerve plexus. This study also indicates that L. pertusa planulae seek out cryptic spaces for settling.     

Dynamic expression of ancient and novel molluscan shell genes during ecological transitions

Background  

The Mollusca constitute one of the most morphologically and ecologically diverse metazoan phyla, occupying a wide range of marine, terrestrial and freshwater habitats. The evolutionary success of the molluscs can in part be attributed to the evolvability of the external shell. Typically, the shell first forms during embryonic and larval development, changing dramatically in shape, colour and mineralogical composition as development and maturation proceeds. Major developmental transitions in shell morphology often correlate with ecological transitions (e.g. from a planktonic to benthic existence at metamorphosis). While the genes involved in molluscan biomineralisation are beginning to be identified, there is little understanding of how these are developmentally regulated, or if the same genes are operational at different stages of the mollusc's life.     

Larval shells of Late Palaeozoic naticopsid gastropods (Neritopsoidea: Neritimorpha) with a discussion of the early neritimorph evolution

Extant neritimorphs with planktotrophic larval development have a convolute smooth larval shell which is internally resorbed. The oldest known larval shells of this type are of Triassic age. Well-preserved Late Palaeozoic neritimorph specimens have larval shells of two or more rapidly increasing well separated whorls. These larval shells resemble planktotrophic caenogastropod larval shells. This type of larval shell is possibly plesiomorphic in neritimorphs and caenogastropods. Permian/Pennsylvanian neritimorphs (Naticopsis, Trachyspird) have smooth larval shells (Naticopsidae) or larval shells with strong axial ribs (Trachyspiridae new family). The convolute low-spired round shell shape of modern neritimorphs is causally linked with the resorption of the inner teleoconch and protoconch whorls. Modern neritimorph shells with a uniform, undifferentiated inner lumen have probably evolved from naticopsid ancestors which lack resorption. It is possible that an elevated spire, deep sutures and protruding spiral larval shells would have made such internally undifferentiated shells more vulnerable for mechanical destruction and prédation. Suggestions that coiling evolved independently in neritimorphs and other Gastropoda are unlikely and contrast with the fossil record. The modern neritid larval shell has probably evolved from relatively low-spired smooth naticopsid larval shells like those reported here.     

An Early Cenomanian (Late Cretaceous) maximum flooding bioevent in NW Europe: Correlation,sedimentology and biofacies

The Early Cenomanian (mid-Mantelliceras dixoni Zone) Schloenbachia/Inoceramus virgatus Event of NW Europe is recorded in five calcareous ‘marl’-limestone couplets rich in inoceramid bivalves of the Inoceramus virgatus plexus. The 1.3–6.8m thick beds represent a bundle of precession couplets inferred to have been deposited during a short-term cycle of sea-level change triggered by the 100kyr short eccentricity cycle within the Milankovitch periodicities. A burrowed omission surface terminates the Schloenbachia/Inoceramus virgatus Event in most places. Rock accumulation rates vary in different sections between 13 and 68Bubnoff units (mm/kyr) for the complete 100kyr cycle with extreme values ranging from 10 to 100Bubnoffs at shorter (i.e., 20kyr precession couplet) scales. Taphonomic and microfacies trends suggest deposition below fair-weather wave base with frequent to sporadic reworking of the sea-floor by storm waves for proximal and medial sections. The distal sections were close to, or even slightly below, maximum storm wave base. The biofacies of the Schloenbachia/Inoceramus virgatus Event is strongly dominated by inoceramid bivalves (65–85%). The two representatives of Inoceramus virgatus, I. virgatus virgatus Schlüter and I. virgatus scalprum Böhm, are not geographic subspecies as they co-occur in the same beds. However, proximal morphs tend to be more strongly ribbed and flatter whereas distal ones are more inflated and smoother, representing ecophenotypes of one polymorphic species. Taphonomic observations and shell morphology suggest that the inoceramids lived as epibyssate recliners. The low species richness and fossil content of the event strata (without the inoceramid bivalves) are attributed to low fluxes of organic matter to the sea-bed during the maximum flooding interval of Cenomanian depositional sequence Ce III. The inoceramids of the virgatus plexus are inferred to have been very effective filter feeders flourishing under nutrient-depleted, low-energy conditions. The Schloenbachia/Inoceramus virgatus Event is an example of a maximum flooding bioevent, forming a widespread marker dominated largely by autochthonous biota.