Post-mortem Transport Research Articles

The ostracod distribution in the Sea of Galilee (Levant): species distribution and post-mortem dispersal of valves and carapaces

The Sea of Galilee is a unique large freshwater or slightly oligohaline natural lake in the Levant. Therefore, it represents an important aquatic habitat in the region that also provides invaluable ecosystem services for the local communities. To improve our knowledge of the lake’s ecosystem and the use of disarticulated ostracod valves and preserved carapaces, micro-crustacean remains commonly used in palaeolimnology and palaeoceanography, as proxies for palaeoenvironmental reconstructions, and to examine the post-mortem dispersal of ostracod remains, 68 surface-sediment samples were collected from the lake bottom in 2012 and analysed for the ostracod assemblages. Both, the noded and smooth, forms of Cyprideis torosa dominate in the Sea of Galilee, with the former more abundant than the latter. Relatively abundant and found at half of the 68 sampling locations or more, are also Ilyocypris hartmanni, I. cf. nitida, Darwinula stevensoni and Neglecandona angulata. In addition, ten less abundant ostracod taxa were recorded in the lake. Of all 15 taxa recorded in our study, ten were also recorded in a study of the Sea of Galilee’s ostracod fauna conducted already in the 1960s. The newly recorded five taxa are relatively rare, and they were mostly found in the region of the Jordan River delta or near the southeastern shore of the lake which were not included in the survey of the 1960s. Thus, there is no evidence for a significant change in the ostracod fauna of the lake over the last half-century. In comparison to the ostracod assemblage from a late Pleistocene archaeological excavation site at the southwestern margin of the lake, the assemblage from the recent survey is slightly less diverse, probably because of the long duration of ca. 5000 years integrated by the sedimentary section of the archaeological site and also due to nearby freshwater inflows from which valves and carapaces were probably washed to the site’s location. Our study also shows that ostracod valves and carapaces are typically relatively abundant in most of the surface-sediment samples collected from locations at 18 m or shallower. In contrast, very few valves and carapaces were recorded at depths greater than 18 m, which is a zone affected by seasonal anoxia in the Sea of Galilee. These few ostracod remains were apparently transported by currents and waves to the central, deeper part of the lake, but their low number shows that such post-mortem dispersal of ostracod remains is insignificant in the deeper part of the lake. Thus, our study provides support for palaeoenvironmental and palaeoclimate reconstructions based on ostracod records from single sediment cores obtained from depths unaffected by post-mortem transport and seasonal or permanent anoxia.

A palaeoecological analysis of the Cretaceous (Aptian) insect fauna of the Crato Formation, Brazil

A rich insect fauna is found in the Cretaceous (Aptian) Nova Olinda Member of the Crato Formation in the Araripe Basin, northeastern Brazil. The Crato Formation was deposited close to the centre of the supercontinent Gondwana, prior to significant rifting. In this paper, we analyzed remains of 1135 insect specimens, representing 55 families, within two limestone facies of the Nova Olinda Member: pale yellow and dark gray limestones. We collected taphonomical data and assessed the paleoecological significance of insect faunas in terms of their distribution and interaction with the paleoenvironment. The insect fauna is dominanted by fully terrestrial taxa despite preservation in an aquatic paleoenvironment. Considering both facies, the distribution of insect families is similar throughout the Nova Olinda Member, which excludes possible overlapping of one entomofauna over another. The pale yellow limestones near the top of the section are richer in fossil insect content and show a higher incidence of aquatic and semiaquatic insects preserved in dorsoventral view compared to the dark gray limestones. This suggests that the Crato insects preserved in the pale yellow limestones experienced short transport distances or prolonged decay or both. In contrast, insects preserved in the dark gray limestones appear proportionally with higher degrees of disarticulation than those preserved in the pale yellow limestones, indicating that these insects underwent a higher degree of postmortem transport in the biostratinomic stage. Compared to descriptions of other Early Cretaceous assemblages, the taxonomic literature of Crato Paleoentomofauna shows distinct differences. The Yixian and Zaza formations are described as being dominated by beetles and wasps. The Crato Formation, however, is relatively richer in Paleoptera species. Both the sedimentary facies studied and the paleoentomological content reveal a complex ecosystem inserted in a depositional setting, similar to modern long-standing wetlands, and where periodically flooded zones were surrounded by dry lands with xeromorphic vegetation.

Spatial distribution, diversity, and taphonomy of clypeasteroid and spatangoid echinoids of the central Florida Keys.

Irregular echinoids are ecosystem engineers with diverse functional services. Documenting present-day distribution of those widespread organisms is important for understanding their ecological significance and enhancing our ability to interpret their rich fossil record. This study summarizes SCUBA surveys of clypeasteroid and spatangoid echinoids conducted in 2020 and 2021 along the central part of the Florida Keys. The survey included observations on both live and dead specimens, their distribution, habitat preferences, abundance, and live-dead comparison. Echinoids were found at 17 out of 27 examined sites (63%) and occurred across a wide range of habitats including coastal seagrass meadows, subtidal sand and seagrass settings of the Hawk Channel, backreef sands, and fine muddy sands of deeper forereef habitats. The encountered species, both dead and alive, included Clypeaster rosaceus (four sites), Clypeaster subdepressus (five sites), Encope michelini (three sites), Leodia sexiesperforata (eight sites), Meoma ventricosa (nine sites), and Plagiobrissus grandis (four sites). All sites were dominated by one species, but some sites included up to five echinoid species. Live-dead fidelity was high, including a good agreement in species composition of living and dead assemblages, congruence in species rank abundance, and overlapping spatial distribution patterns. This high fidelity may either reflect long-term persistence of local echinoid populations or fragility of echinoid tests that could prevent post-mortem transport and the formation of time-averaged death assemblages. Regardless of causative factors, the live-dead comparisons suggest that irregular echinoid assemblages, from settings that are comparable to the study area, may provide a fossil record with a high spatial and compositional fidelity. The survey of live fauna is consistent with past regional surveys in terms of identity of observed species, their rank abundance, and their spatial distribution patterns. The results suggest that despite increasingly frequent hurricanes, active seasonal fisheries, massive tourism, and urban development, irregular echinoids continue to thrive across a wide range of habitats where they provide diverse ecosystem services by oxygenating sediments, recycling organic matter, supporting commensal organisms, and providing food to predators. Results reported here document the present-day status of local echinoid populations and should serve as a useful reference point for assessing future regional changes in echinoid distribution and abundance.

Taphonomic overprinting on the late Palaeozoic terrestrial plant–animal interactions: a noise in the record

Plant–animal interactions investigated largely in Glossopteris leaf fossils (1214 specimens) from the lower Permian strata of peninsular India reveal evidence of taphonomic modifications of the ichnofabric. The leaf fossils indicate both above-ground (pre-depositional) and on-ground (post-depositional) animal activities. Animal traces that extend beyond the margins of the leaf compressions or are emplaced on the leaf impressions are evidently post-depositional, preserved ex situ. Both feeding (herbivory/detritivory) and locomotary animal traces are interpreted in the host media. Preserved traces in the leaf fossils depict arrays of pre- and post-depositional events (viz., biotic interactions on green foliage, leaf detachment from the trees, post-mortem transport and burial) along taphonomic pathways. Accordingly, five taphonomic pathways are proposed based on varied combinations of pre- and post-depositional traces, emplaced on leaf fossils. Low diversity and persistent rarity of post-depositional traces (4%) as compared to more common pre-depositional traces (7%) in the sample population are noted. Less common post-depositional trace fossil assemblages of depauperate diversity indicate that stressed habitats prevailed at the depositional sites and a limited time window for preservation of plant–animal interactions. The recognition of pre- and post-depositional trace fossil suites ensures ichnological and ethological fidelity of faunal data on plant–animal interactions.

The role of taphonomy in cladistic analysis: A case study in Permian bivalves.

The Megadesmidae (Bivalvia, Anomalodesmata) fossil record was examined in order to assess the role of taphonomy in cladistic analysis. Megadesmids are thick-shelled, infaunal, suspension-feeding bivalves. Our data indicate that their fossil record seems biased in favor of thick-shelled, shallow-burrowing genera and/or deep­burrowing forms. Consequently, there is a relation between the mode of life (shallow versus deep) and the resolution and quality of the fossil record. Deep-burrowers (Vacunella) are often preserved in life position offering a more accurate (temporal and spatial) fossil record, adequate for paleoecological inferences, while shallow-burrower shells (Plesiocyprinella), that are more prone to post-mortem transport and temporal mixing, offer a record with poor spatial and temporal resolution. The identification of homoplasy among infauna! bivalves constitutes a major challenge for their cladistic analysis. Within Megadesmidae intrinsic (bauplan limitations) and extrinsic (better preservational potential) factors favor the occurrence and preservation of homoplasy among the deep-burrowers. The implications are: a) clustering of deep-burrowing bivalves (Vacunella, Roxoa) due to parallel homoplasies, forming "adaptive", not necessarily "evolutive" taxa, and b) lower consistency indices in their cladistic analysis.

New record of podocopid ostracods from Cretaceous amber.

Burmese Cretaceous amber (∼99 Ma, Myanmar) is famous for the preservation of a wide range of fauna and flora, including representatives of marine, freshwater and terrestrial groups. Here, we report on three ostracod specimens, that came visible as syninclusions to an aquatic isopod. The three specimens represent three different taxa, that were found preserved in a single piece of amber. One of the described specimens was studied using µCT scanning data. On the basis of general carapace morphology we assign all three to the group Podocopida, and (tentatively) its ingroup Cypridocopina. A lack of visibility of more particular diagnostic features such as adductor muscle scars and details of the marginal zone precludes a further identification, but we discuss possible affinities with either the marine-brackish group Pontocypridoidea or the non-marine group Cypridoidea. The taphonomy indicates that the studied ostracods had been subject to limited (if any) post-mortem transport, which could be consistent with marginal marine environments.

Osteology and phylogeny of small-bodied hadrosauromorphs from an end-Cretaceous marine assemblage

Abstract The timing of non-avian dinosaur decline is one of the most debated subjects in dinosaur palaeontology. Dinosaur faunas from the last few million years of the Mesozoic appear far less diverse than those from earlier in the Cretaceous, a trend that could suggest non-avian dinosaur extinction occurred gradually. However, the limited nature of the latest Cretaceous dinosaur record outside western North America has obscured patterns in dinosaur diversity just before the extinction. Here, I describe two associated skeletons and several isolated fossils recovered from the New Egypt Formation of New Jersey, a latest Maastrichtian unit that underlies the K–Pg boundary. The larger skeleton appears to be a small-bodied adult from a lineage outside Hadrosauridae, the dominant group of these animals during the Maastrichtian, that persisted along the eastern coast of North America. Smaller specimens are identifiable as juvenile hadrosauromorphs. These results substantiate an important assemblage of herbivorous dinosaurs from the poorly-known Cretaceous of eastern North America. The marine depositional setting for these skeletons demonstrates that proposed ecosystem preferences among hadrosauromorphs may be biased by post-mortem transportation, and the adult skeleton has implications for assessing the proposed relictual nature of Late Cretaceous eastern North American vertebrates.

Spatial distribution of oncocerid cephalopods on a Middle Devonian bedding plane suggests semelparous life cycle

Reproductive strategies of extinct organisms can only be recognised indirectly and hence, they are exceedingly rarely reported and tend to be speculative. Here, we present a mass-occurrence with common preservation of pairs of late Givetian (Middle Devonian) oncocerid cephalopods from Hamar Laghdad in the Tafilalt (eastern Anti-Atlas, Morocco). We analysed their spatial occurrences with spatial point pattern analysis techniques and Monte Carlo simulations; our results shows that the pairwise clustering is significant, while ammonoids on the same bedding plane reveal a more random distribution. It is possible that processes such as catastrophic mass mortality or post-mortem transport could have produced the pattern. However, we suggest that it is more likely that the oncocerids were semelparous and died shortly after mating. These findings shed new light on the variation and evolution of reproductive strategies in fossil cephalopods and emphasise that they cannot be based on comparisons with extant taxa without question.

Pre-burial taphonomic imprints on drilling intensity: a case study from the recent molluscs of Chandipur, India

ABSTRACT Palaeoecological studies of drilling intensity (DI), drawing ecological and evolutionary inferences, generally assume that drilled and undrilled specimens are equally preserved in the fossil record, because of the fact that the presence of drillholes does not affect preservation potential during sediment compaction. However, another facet that has not been studied conclusively is the taphonomic imprint on DI in a pre-burial scenario. If drillholes add weakness to a shell’s mechanical strength, drilled valves may preferentially be broken during post-mortem transportation, before its’ burial within sediment. In the present study, we test this hypothesis with a dataset involving DI and taphonomic status of two bivalve, Donax scortum and Mactra luzonica and two gastropod, Natica tigrina and Turricula javana species from Chandipur, India. Taphonomic status of each specimen is determined by relative preservation of its’ morphological characters. In case of both bivalves and gastropods, DI is found to be highest among the best preserved specimen and, thereafter, declines with increasing taphonomic degradation. When shell size is included in analyses, DI still shows an inverse relation with taphonomic alteration. This observed inverse relationship between drilling intensity and taphonomic imprint suggest that drilled shells may be vulnerable to breakage by pre-burial taphonomic processes.

Impact of bottom water currents on benthic foraminiferal assemblages in a cold-water coral environment: The Moira Mounds (NE Atlantic)

Abstract Strong bottom currents play a key role in cold-water coral environments by shaping their morphology and providing the necessary food for the corals to thrive. This study investigates the differences between living and dead benthic foraminiferal assemblages in such environments, more precisely on the Moira Mounds (NE Atlantic). A specific focus is to understand the role of currents and their influence on the taphonomy of benthic foraminiferal assemblages. Here, we analyze high-resolution sediment grain size distributions coupled with benthic foraminiferal assemblage composition to assess how much deep-sea bottom currents affect benthic foraminiferal assemblages. We suggest that the dead benthic foraminiferal assemblage consists of a reworked glacial fauna associated with contemporary species. Reworked glacial species (Elphidium excavatum, Sigmoilopsis schlumbergeri) are the most abundant. Dominant species that are present almost exclusively in the living assemblage (Alabaminella weddellensis, Nonionella iridea, Trifarina spp.) are associated with high phytodetritus input, possibly as a response to the later phase of the North-east Atlantic spring bloom. Dead assemblages are further characterized by the scarcity of organic-walled agglutinated foraminifera in comparison to living assemblages. Sediment grain size distributions show that the downslope Moira Mounds consist of well-sorted fine sand, typical of contourite deposits in the area. Grain size distributions and the average Shannon diversity of living and dead foraminiferal assemblages indicate that the coral cover offers a sheltered environment, baffling eroded sediment and preventing post-mortem transport of dead foraminifera. We conclude that cold-water coral environments provide a valuable paleoenvironmental archive by trapping sediment in an otherwise non-depositional system.

Distribution and Characteristics of Polyphenoloxidase from Pacific White Shrimp (Litopenaeus vannamei).

Distribution of polyphenoloxidase (PPO) from different anatomical parts of Pacific white shrimp was examined. Among all parts, cephalothorax possessed the maximal PPO activity (P < 0.05), followed by pereopods, telson, pleopods, carapace, cuticle, and muscle, respectively. The higher PPO activity in cephalothorax was in line with the greater melanosis in this part during chilled storage. According to activity-staining toward 3,4-dihydroxy-ʟ-phenylalanine (ʟ-DOPA), PPO exhibited an activity band with a molecular weight (MW) of 210 kDa. When cephalothorax PPO was purified using ammonium sulfate precipitation and a series of chromatographic techniques, involving DEAE-Sepharose anion exchange and Sephadex G-75 gel filtration columns, homogeneity was obtained. Based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and native-PAGE, the Sephadex G-75 fraction showed a single band. The MW band on SDS-PAGE and gel filtration was estimated as 210 kDa, suggesting a monomeric molecule. For the inhibitor study, cysteine and 4-hexylresorcinol showed competitive inhibition toward PPO, while epigallocatechin gallate and kojic acid demonstrated mixed-type inhibition toward PPO. PRACTICAL APPLICATION: Melanosis (black spot formation) triggered by polyphenoloxidase (PPO) drastically reduces the shelf-life of shrimp. PPO was localized in several anatomical parts of Pacific white shrimp with varying activities. Certain compounds, including cysteine, 4-hexylresorcinol, epigallocatechin gallate, and kojic acid, showed PPO inhibitory activity with different modes of inhibition. The obtained information provided a promising method for manufacturers to keep the prime eating quality of Pacific white shrimp throughout postmortem transportation and storage using selected PPO inhibitors.

Late Jurassic (Kimmeridgian) sea lilies (Crinoidea) from central Poland (Łódź Depression)

Upper Jurassic (Kimmeridgian) limestones of central Poland (southern border of the Łódź Depression) are in places extremely rich in crinoid remains. These latter are represented by very well preserved columnals/pluri-columnals, isolated brachials and cirrals/pluri-cirrals, assignable to the following species: Isocrinus amblyscalaris (Thurmann, in Thurmann and Éttalon), Isocrinus cf. pendulus (von Meyer), Balanocrinus brachiospina Hess, Balanocrinus pentagonalis (Goldfuss), Balanocrinus subteres (Münster, in Goldfuss), Balanocrinus sp., and Millericrinida indet. The commonest species, Balanocrinus brachiospina, is recorded for the first time from Poland. Critical revision of Polish occurrence of balanocrinids is provided. It is suggested that some of the previous balanocrinid finds from Poland assigned to Balanocrinus subteres should be now addressed as B. brachiospina. Furthermore, it is probable that the Callovian B. hessi Salamon and Zatoń should be synonymized with B. pentagonalis. Crinoid material at hand is also associated with asteroid and echinoid remains. Among this material, a complete test of Pleurodiadema nudum Cotteau is illustrated for the first time from Poland. Taphonomic observations of echinoderms from the Kimmeridgian limestones of the Łódź Depression suggest that they did not undergo a long post-mortem transport. The high degree of disarticulation, however, supports their prolonged post-mortem seafloor exposure.

Close-range photogrammetry of the Cleveland-Lloyd Dinosaur Quarry, Upper Jurassic Morrison Formation, Emery County, Utah

Bone distribution data are essential for taphonomic assessments of bonebeds. The Cleveland-Lloyd Dinosaur Quarry (CLDQ), an Allosaurus-dominated bonebed within the Upper Jurassic Morrison Formation, has been researched for nearly 100 years, but published maps are scarce considering the impor¬tance and density of the assemblage. Additionally, few detailed maps of bones from the CLDQ have been published in two dimensions, whereas the third, the stratigraphic/vertical, dimension has never been recorded. Utilizing standard field mapping techniques as well as photogrammetry, the three-dimensional orientations of bones currently exposed in the quarry have been analyzed for potential dispersal patterns. Additionally, a “living” or continuously updatable, photogrammetric map which allows for researchers to view the bones in three dimensions throughout the course of excavation has been created. Continued photogrammetry in future field seasons will allow visualization of bones in three dimensions even after the currently exposed bones have been removed. Utilizing these newly available data, two distinct clusters of bone within the South Butler Building at the quarry are identified. Based on statistically significant average orientations and depths of these bones, early-stage post-mortem transport of carcasses prior to disarticulation (i.e., bloat and float) is supported as an important transport and depositional process within the quarry assemblage. Furthermore, possible evidence of multiple depositional events is discussed.

Postmortem transport in fossil and modern shelled cephalopods.

The chambered shells of cephalopod mollusks, such as modern Nautilus and fossil ammonoids, have the potential to float after death, which could result in significant postmortem transport of shells away from living habitats. Such transport would call into question these clades’ documented biogeographic distributions and therefore the many (paleo)biological interpretations based on them. It is therefore imperative to better constrain the likelihood and extent of postmortem transport in modern and fossil cephalopods. Here, I combine the results of classic experiments on postmortem buoyancy with datasets on cephalopod shell form to determine that only those shells with relatively high inflation are likely to float for a significant interval after death and therefore potentially experience postmortem transport. Most ammonoid cephalopods have shell forms making postmortem transport unlikely. Data on shell forms and geographic ranges of early Late Cretaceous cephalopod genera demonstrate that even genera with shell forms conducive to postmortem buoyancy do not, in fact, show artificially inflated biogeographic ranges relative to genera with non-buoyant morphologies. Finally, georeferenced locality data for living nautilid specimens and dead drift shells indicate that most species have relatively small geographic ranges and experience limited drift. Nautilus pompilius is the exception, with a broad Indo-Pacific range and drift shells found far from known living populations. Given the similarity of N. pompilius to other nautilids in its morphology and ecology, it seems unlikely that this species would have a significantly different postmortem fate than its close relatives. Rather, it is suggested that drift shells along the east African coast may indicate the existence of modern (or recently extirpated) living populations of nautilus in the western Indian Ocean, which has implications for the conservation of these cephalopods.

Preservation of borings: contrasting examples from the type Maastrichtian (Upper Cretaceous), southern Limburg, the Netherlands

The taphonomy of trace fossils and their substrates remains an understudied facet of sedimentary geology. Contrary to common prejudice, trace fossils are not invariably preserved in situ, but may be exhumed and reworked following lithification. The trace fossils most commonly found ex situ are borings in mobile shelly substrates. Two notable, but contrasting, examples of post-mortem transport of borings are described from the Maastrichtian (Upper Cretaceous) of southern Limburg, the Netherlands. A long, unusually straight and complete calcareous tube assigned to Teredolites longissimus Kelly and Bromley is an organically secreted internal mould, produced by a teredinid or pholadid bivalve boring in wood and lining their tube. Strictly, this is part of the body fossil of the producing bivalve, but it is also an organically generated internal mould of the boring. A flint steinkern of a right valve of Crassatella bosquetiana d’Orbigny preserves a suite of silicified borings. Caulostrepsis taeniola Clarke is a U-shaped boring with a vane connecting the parallel limbs. Talpina isp. is a slender, simple, branched tunnel. Most unexpected, Spirichnus spiralis Fürsich et al. is a spiral ‘worm’ boring hitherto only known from the Upper Jurassic. This stratigraphic gap is likely an artefact; only mouldic preservation of the bored substrate would expose the distinctive Spirichnus boring. These ichnofossils are united in their occurrence in unusual preservational systems.

Cyprideis torosa(Jones, 1850) in its type area and stratigraphical context: potential for mapping the freshwater/estuarine boundaries of the Thames–Medway river system in the MIS 9 and MIS 11 interglacials

This study explores the potential of the ostracod Cyprideis torosa (Jones, 1850) as a brackish-water indicator for mapping freshwater/estuarine boundaries in Pleistocene interglacials in SE England. Ostracod species records from MIS 9 (Purfleet) and MIS 11 (Hoxnian) interglacial sites are mapped onto established palaeogeographies of the Thames–Medway river system, revealing distribution patterns indicative of a salinity gradient from west (freshwater) to east (brackish estuarine) in both cases. Comparisons with the ostracod biofacies of the present-day Thames Estuary suggest there may be no exact modern analogue for the Thames/Medway palaeoenvironments of the MIS 9 and MIS 11 interglacials. A similar conclusion is drawn from discussion of noding in C. torosa , which is common in the interglacial assemblages but extremely rare in the modern estuary. The value of mapping C. torosa onto estuarine palaeogeography is limited by taphonomic considerations because post-mortem transport and mixing in a macrotidal estuary significantly influence the composition of ostracod assemblages. Nevertheless, its use in combination with other brackish-water taxa provides useful insights regarding the palaeosalinity regimes of the lower River Thames and River Medway during the MIS 9 and MIS 11 interglacials.

High dead-live mismatch in richness of molluscan assemblages from carbonate tidal flats in the Persian (Arabian) Gulf

Live-dead (LD) fidelity studies are a fundamental tool for assessing the quality of the paleobiological information preserved in the fossil record. An important feature of death assemblages (DAs) is that they are time-averaged to some degree. Previous studies found that subtidal carbonate environments are characterized by lower time-averaging in comparison to siliciclastic settings, primarily because of a high rate of shell loss due to bioerosion and dissolution. These factors lead to increased temporal resolution in subtidal carbonate death assemblages (DAs) but more intense bias in species composition due to differential loss of vulnerable shells. A consequence of lower time-averaging is a better match in live-dead (LD) richness. We evaluated LD fidelity of molluscan assemblages from soft sediments in subtropical, carbonate tidal flats along the coast of the United Arab Emirates (Persian (Arabian) Gulf) to test these predictions. A total of 7193 mollusks from six sites were analyzed. We found that DAs are, on average, over five times richer than living assemblages (LAs) at site scale, and nearly five times at habitat scale. We found that early cementation, lateral mixing, intense bioturbation and moderate sedimentation rates can account for large LD differences in richness. Differential intensity in lateral mixing by post-mortem transport inflated alpha, beta, and gamma diversity by 28, 10 and 42%. However, beta diversity is strongly underestimated in DAs when compared to LAs. Evenness was larger in DAs both at site and at habitat scales, but there was only a high mismatch at sites with patchy LAs. Fidelity of feeding guild structure was high for rank abundance, with secondary consumers well represented in DAs. The occurrence of out-of-habitat taxa did not affect fidelity in rank-abundance of feeding guild structure. Our results suggest that time-averaging in carbonate tidal flats can potentially be higher compared with subtidal carbonate environments.

Temporal and bathymetric resolution of nautiloid death assemblages in stratigraphically condensed oozes (New Caledonia)

AbstractCephalopod shells can be affected by postmortem transport and biostratigraphic condensation, but direct estimates of the temporal and spatial resolutions of cephalopod assemblages are missing. Amino acid racemisation calibrated by 14C demonstrates a centennial‐scale time averaging (&lt;500 years) of Nautilus macromphalus in sediment‐starved, epi‐ and mesobathyal pelagic environments. The few shells that are thousands of years old are highly degraded. The median occurrence of dead shells is at 445 m depth, close to the 300–400 m depth where living N. macromphalus are most abundant. Therefore, dead shells of this species accumulate at a centennial temporal resolution and with excellent bathymetric fidelity. Dead Nautilus shells exist for only a few hundred years on the seafloor, in contrast to the biostratigraphically condensed mixture of extant foraminifers and foraminifers that went extinct during the Pleistocene. Cephalopod shells that do not show any signs of early diagenetic cementation are unlikely to be biostratigraphically condensed.

Middle-to-Late Pleistocene malacofauna from the archeopaleontological site of Oued Sarrat (Tajerouine area, NW Tunisia)

The malacofauna collected from the archeopaleontological site in Oued Sarrat (Tajerouine area, NW Tunisia) is the first reference from the Middle and Late Pleistocene stratigraphic series in Tunisia. These malacologic assemblages are abundant but little diversified; they are considered as continental, lakeside, and fluviatile ecosystem forms. They are associated with bones of small and large vertebrates and lithic artifacts. The dominant species of gastropods are Cernuella virgata (Da Costa, 1778), Xerosecta cespitum (Draparnaud, 1801), and Sphincterochila baetica (Rossmassler, 1854) which are typical of the Mediterranean regions. The abundance of these pulmonate terrestrial gastropods indicates a post-mortem transport of shells by floods and fluvial channels. The only bivalve, Unio ravoisieri (Deshayes, 1847), still common in the rivers of northern Tunisia, characterizes a typical lakeside environment, with relatively low energy. Considering the recently discovered associated vertebrate remains, their occurrence corroborates the onset of a paleoenvironment landscape with swamps, or even a shallow freshwater paleolake with close forests. Hence, this environment also inhabited by a diversity of large mammal species and other abundant microvertebrates and invertebrates was a support for human survival within these northern African latitudes.

Concentrations of silicified cephalopods within upper Frasnian carbonate concretions from the Holy Cross Mountains, Poland

Concentrations of silicified juvenile cephalopods from upper Frasnian carbonate nodules from the Jaźwica quarry in the Holy Cross Mountains are described here for the first time. Using conodonts, the age of the investigated cephalopod-rich nodules has been determined as the linguiformis conodont Zone, and may correspond to the Upper Kellwasser Event. The concentrations of silicified juvenile ammonoids described here resulted from a combination of biological and physical factors related to environmentally-driven mass mortality (induced by storms and perhaps additionally by anoxia) following mass spawning and post-mortem transport with the aid of bottom currents, which enabled them to drift to small depressions on the sea floor. Rapid silification led to excellent preservation of the fossil assemblage.