Taphonomic Features Research Articles

Late Jurassic (Kimmeridgian) bivalves from northwestern Algeria (Daïa and Nador mountains): Systematics and palaeobiogeography

The bivalve fauna of the Upper Jurassic (Kimmeridgian) successions belonging to the Daïa and Nador mountains (NW Algeria) is taxonomically described and figured. For the first time, sixteen bivalve taxa were identified, partly in open nomenclature because of their poor state of preservation. Most taxa are represented by internal casts. The fauna was collected from two different formations of the same age: the Dolomies de Tlemcen Formation in the Daïa Mountains and the Faïdja Formation in the Nador Mountains. The lithologic characteristics of these formations, together with their fossil content and taphonomic features, confirm that these localities are characterized by marine conditions. The north-western Algerian bivalve assemblage holds the largest portion of cosmopolitan species.

Anthropogenic modification of a giant ground sloth tooth from Brazil supported by a multi-disciplinary approach

Identifying evidence of human modification of extinct animal remains, such as Pleistocene megafauna, is challenging due to the similarity of anthropogenic and non-anthropogenic taphonomic features observed under optical microscopy. Here, we re-investigate a Late Pleistocene ground sloth tooth from northeast Brazil, previously suggested as human-modified based only on optical observation. To characterize the macro- and micro-morphological characteristics of the marks preserved in this tooth and evaluate potential human modification, we used stereomicroscope and scanning electron microscopy (SEM) supplemented by energy dispersive spectroscopy (EDS), UV photoluminescence (UV/PL), synchrotron-based X-ray fluorescence (SR-XRF), and synchrotron micro-computed tomography (SR-µCT). These methods allowed us to discriminate non-anthropogenic taphonomic features (root and sedimentary damage), anthropogenic marks, and histological features. The latter shows the infiltration of exogenous elements into the dentine from the sediments. Our evidence demonstrates the sequence of anthropogenic and non-anthropogenic taphonomic modification of this tooth and supports its initial intentional modification by humans. We highlight the benefits of emerging imaging and spectral imaging techniques to investigate and diagnose human modification in fossil and archaeological records and propose that human modification of tooth tissues should be further considered when studying possibly anthropogenically altered fossil remains.

Morphology and taphonomy of the gastropod Terebralia palustris from an iron age site in the Arabian Peninsula

The Indo-Pacific gastropod Terebralia palustris is particularly suitable for comparing natural and anthropogenic induced taphonomic pathways due to its wide geographic distribution and common presence within archeological context. The present study aims to (1) correlate shell architecture and morphology with fragmentation pattern and preservation, (2) quantify taphonomic changes to differentiate between natural vs. anthropogenic preservation features, (3) provide a guideline for analyzing fragmented shell remains in archeological material. Shells and taphonomic features were studied from both recent mangrove environments from the Emirate of Sharjah, United Arab Emirates as well as archeological material within the Iron age II site (1000–600 BC) of Muweilah near the City of Sharjah. Techniques utilized include morphometry, thin sectioning, scanning electron microscopy (SEM) of recent specimens and a semi—quantitative taphonomic analysis of anthropogenic material. Thin sectioning shows a complex internal shell morphology with a tripartite subdivision of shell layers. The recent material shows better preserved features on both the exterior and internal shell surfaces than the highly fragmented material recovered from the archeological context, which shows a distinct size distribution as well as showing higher levels of surface abrasion, surface cracks and color alterations. These features are correlated to extraction techniques, cooking methods and waste disposal handling.

Not all shell beds are made equal: Recognizing singular event‐concentrations in megalakes

ABSTRACTEvent deposition accounts for a large part of the preserved sedimentary record. Tempestites, tsunamites and turbidites are among the most common event deposits in marine and lacustrine systems. While facies models exist for these deposits, the challenge lies in the fact that diverse triggers can give rise to analogous depositional processes and comparable taphonomic features, making it difficult to pinpoint the precise trigger for an event bed. Hence, five distinct modern‐type shell concentrations are studied in Permian strata from the Paraná Basin, West Gondwana, to access the parameters to discriminate event phenomena, and their associated depositional and taphonomic processes. During this time interval, the basin underwent continuous continentalization due to orogenic events, leading to the entrapment of epeiric marine waters and the transformation of the system into a megalake, supporting a diverse and endemic freshwater bivalve fauna. While sedimentation was primarily influenced by meteorological events, certain stratigraphic intervals were also affected by tectonically active periods and meteor impact events. The different products are categorized into bioclastic sandstone, shell bed, shell‐rich phosclast rudstone and shell‐rich conglomerate that are interpreted as proximal and distal tempestites and tsunamites, respectively. Finally, the products and the processes that lead to the deposition of tempestites and tsunamites are compared to establish diagnostic signatures that may be applied to differentiate these event concentrations in analogous settings from the geological record.

CSI (Crime Scene Investigation) Beagle: Darwin's contribution to taphonomy

In the last decades, the impact of Darwin's legacy has been emphasized in many scientific fields. Nevertheless, there are still lesser-explored aspects of his life as researcher that deserve attention, such as his role as taphonomist. In this context, we highlight here this relevant facet of Darwin's investigations. During his voyage on the H.M.S. Beagle, Darwin collected numerous vertebrate fossils from South America. Particularly, in the Argentine Pampas he recorded information on the paleontology, stratigraphy, and sedimentology of different late Cenozoic fossiliferous sites. He also made observations on the preservation features of bone remains and the mechanisms that favored their fossilization, aspects currently included in the taphonomy field. In this frame, the information published in Geological Observations on South America regarding the fossils from Monte Hermoso and Punta Alta sites and his comments about the “imperfection of the geological record” on the Origin of the Species, are particularly noteworthy as an indicator of his interest in the relationship between the environmental context of preservation and the taphonomic features of bone remains. After 150 years, his scientific work continues to fascinate us. Darwin's keen eye for detail and his curiosity about the history of each fossil, about a century before taphonomy was born as a discipline, can indeed be likened to that of a Crime Scene Investigator (CSI) in some regards, reconstructing the taphonomic histories of both single remains and whole assemblages.

The case of a mass death of livestock in the Early Iron Age in the steppe zone of Kazakhstan

A mass burial of complete and almost complete cattle and small ruminant skeletons found in a pit within the Early Iron Age settlement of Abylai in Central Kazakhstan (49°15'N, 75°07'E) has been studied. The results of archaeological research and archeozoological contexts have shown that the animals’ burial was a single event. The aim of the work was to determine the reasons for the formation of this accumu-lation. The analysis of skeletal element composition, animal age composition, and the season of their death has been performed. A com-parison of species composition, skeletal element composition, age composition, season of animals’ death and taphonomic features be-tween samples from the pit and the cultural layer of the settlement has been made. Significant differences between these samples have been revealed. The animals from the settlement layer were slaughtered during late autumn-winter, while animals from the pit died in early spring. The bones from the pit were almost all intact, while those from the settlement layer had characteristics typical of household waste. Bones from the “layer” have significantly more postmortem modifications than those from the “pit”. The age composition and the skeleton parts ratio between the samples are different. The analysis of the obtained data shows that in the beginning of spring 89 small ruminant and 6 cattle individuals were buried in the pit in a short period of time. According to ethnographic data, this could possibly be interpreted as the burial of animals who died as a result of spring jute. In the steppe zone of Eurasia, jute is the most frequent extreme event leading to mass death of ungulates. Jutes can happen in summer, when grass burns out with drought. But the most large-scale and frequent are winter jutes, when, due to catastrophic snowfalls, grass becomes inaccessible to animals, and spring jutes, when frosts come after a thaw. During jute, many animals die from starvation in a short time. Small ruminants are the most vulnerable because they are the least adapted to breaking ice crusts with their hooves. Cattle are less vulnerable, and even less so are horses. The following archaeological situation has been observed: all animals died in early spring; many of them were buried in a short time; the remains of small ruminants prevail, there are few cattle and no horses; most animals were probably skinned. This picture is most consistent with the burial of animals killed by jute. As an alternative hypothesis, a sacrificial nature of death of the animals has been considered. However, the combination of characteristics of the archaeological and archeozoological contexts of pit filling allows us to reject the latter hypothesis.

Palaeontological and taphonomical investigations of the exceptionally rich concentration of Miocene vertebrate coprolites from Pécs-Danitzpuszta (Hungary, Mecsek Mts.)

ABSTRACT Thousands of coprolites have been collected from the Upper Miocene (Tortonian/Pannonian) sands of the Pécs-Danitzpuszta sand pit, one of the most important mixed Neogene vertebrate localities in Hungary. Although, the locality has been known for centuries, the coprolites have not been investigated in detail. We describe these fossils and explore their palaeoecological significance. Coprolites were examined with thin sections, X-ray powder diffraction and computed tomography. Their surface is mostly smooth, desiccation cracks were not observed. All coprolites mainly consist of apatite, indicating most probably a carnivorous diet. No evidence of herbivory has been found so far. The coprolites contain remains belonging to several groups: ostracod carapaces, bivalve shells, vertebrae from bony fishes, fish scales, as well as teeth. The CT scans show inhomogeneities in the matrix; however, in most cases they do not reliably indicate inclusions. The taphonomical features suggest rapid burial and most likely an aquatic origin. The spiral morphotype could be attributed to fishes with spiral intestinal valves. Teeth of reef-associated fish taxa indicate Badenian age for some specimens, though the coprolite assemblage might include older and younger specimens as well.

Well‐drained floodplain taphonomic mode of Late Pleistocene vertebrates from northwestern Argentina

ABSTRACTThe vertebrate assemblage recovered from the Toropí/Yupoí Formation (Late Pleistocene) in the Arroyo Toropí area, Bella Vista (Corrientes Province, Argentina), has been subjected to taphonomic evaluation. The fossil‐bearing levels have been dated to ~53 ka (MIS 3) based on Optically Stimulated Luminescence dating. This assemblage primarily comprises mammal remains, with a notable prevalence of herbivorous megamammals. Also, reptiles and birds have been documented. Sedimentological analysis suggests that the skeletal remains were preserved within a floodplain environment influenced by the dynamics of the adjacent fluvial system, and taphonomic features observed in the assemblage support this interpretation. The assemblage resulted from the deposition of disarticulated mammal remains and local dispersion over a relatively short period. Rapid burial is evident, but several processes such as weathering and breakage have contributed to the observed patterns. The loss of several skeletal elements within the assemblage may be attributed to sporadic water flows occurring on the floodplain. During the post‐burial stage, the specimens were affected by diagenetic processes, including filling, impregnation, deformation and breakage. In summary, the taphonomic evaluation of the Toropí/Yupoí Formation offers valuable comparison with other fossil fluvial assemblages. This research contributes to our understanding of the processes and environmental conditions that shaped this Late Pleistocene ecosystem.

The study of dental status through determination of the degree of preservation of paleoanthropological material.

Aim: To introduce a simple classification system for the degree of preservation and quality of the dentoalveolar apparatus into scientific circulation to further investigate dental diseases in ancestral populations.. Materials and Methods: The sample analyzed consisted of the remains of 499 individuals from the human populations that existed in the territories of Ukraine from the Copper Age to the Bronze Age. Teeth and jaws were examined macroscopically under bright light; dental changes were evaluated by probing. Dental radiographic examinations were performed using retroalveolar and panoramic X-ray films in adult individuals. Results: The authors divide the dentoalveolar apparatus of fossil and subfossil skeletons into ten levels for further medical investigation of dental diseases. These levels depend on the preservation degree and changes in jaws and teeth. Conclusions: The study of bone and tooth preservation, determination of skeletal sex, and age characteristics is a separate section and stage in reconstructing the physical type of individuals and the health status of a community. Studying the taphonomic features of odontologic anthropological material should be a mandatory prerequisite preceding its analysis in paleopathology. The condition of the dentoalveolar system can be classified into ten levels for paleopathological conclusions. This classification will be helpful to doctors specializing in forensic medicine and anthropologists.

NEW QUANTITATIVE DESCRIPTORS (SHAPE AND MACROBORING) OF BIOGENIC NODULES: EXAMPLES FROM THE LESSER ANTILLES AND NEW ZEALAND

Abstract Encrusting (Ei), Macroboring (Mi), and Dissymmetry (Di) indices are proposed as quantitative descriptors of biogenic nodules. (Ei) measures the amount of encrustation, (Mi) the contribution of boring traces affecting the internal structure of nodules, and (Di) the regularity of the biogenic accretion around the nucleus. The latter has been used to construct a classification scheme of possible shapes for encrustations. Raw data to calculate the indices were obtained from numerical treatments of digitized photographs of nodule cross-sections. The morphometric (Di) and taphonomic (Ei and Mi) indices have been calculated for carbonate nodules from subtidal temperate and tropical settings in New Zealand (Flat Point Beach) and in the Caribbean (St. Bartholomew Island), respectively. Results for nucleated rhodoliths collected from shallow high-energy settings in these two climatic settings show that their morphometric and taphonomic characters are not species-specific (Lithoporella/Mastophora rhodoliths from St. Barth, and Lithothamnion-Sporolithon rhodoliths from New Zealand), but depend instead on hydrodynamic conditions and on the original shape of nuclei. Acervulinid macroids sampled in deeper waters (28 m) off St. Barth are nucleus-free and have a Macroboring index (Mi) significantly higher than that of rhodoliths from shallower environments, due to discontinuous influence of waves and currents, and low sedimentation rates. The quantitative descriptors proposed here might: (1) complement the characterization of biogenic nodules in specific depositional environments; (2) aid in hydrodynamic and paleoenvironmental reconstructions of biogenic nodule-bearing deposits; and (3) constitute valuable tools in future comparative studies.

Taphonomic damage of molluscan shells in the Nile Delta under natural and anthropogenic sources of environmental variability

Environmental reconstruction can benefit from the interpretation of the postmortem history of shell remains. The molluscan death assemblages obtained from grab samples at forty-nine sites in the Manzala lagoon, the largest lagoon in the Nile Delta, were analyzed to infer the taphonomic alteration. The preservation of shells at each site has been semi-quantitatively ranked based on the taphonomic features formed by encrustation, bioerosion, abrasion, dissolution, precipitation, fragmentation, discoloration, and loss of sheen (low, moderate, high). A significant difference has been observed between sites of low and high environmental stress. Water depth and substrate type (hydrodynamics) correlate significantly to the percent number of altered shells. The southern parts of the lagoon, which are characterized by lower water energy and higher rates of sedimentation, are highly polluted by heavy metals (Cd, Pb, Zn) and organic pollutants. The southern parts receive much sediment from the agricultural drains, which increases burial of shelly material and decreases their time on the TAZ. The northern parts of the lagoon have slower rates of sedimentation, so that the molluscan shells remain longer at the sediment-water interface (Taphonomic Active zone; TAZ), where fragmentation is enhanced by winnowing under higher water-energy. The long residence in the TAZ also favored both bioerosion (Trypanites and Oichnus) and encrustation by bryozoan colonies, polychaetes, and oysters. Therefore, the taphonomic processes have the potential to cause severe damage and taphonomic loss of shell materials. Chemical dissolution and precipitation of shell remains may be related to acidic pore water. Moreover, high alkalinities in the southern polluted parts may also reduce the dissolution in contrast to the acidic water in the northern parts of the lagoon.

Coquina depositional model, Buzios Field, Brazil

Increasingly relevant as petroleum reservoirs, the coquina deposits of the pre-salt section of the Santos and Campos Basin display a wide variety of sedimentary systems that reflect a complex storm-dominated depositional environment. This complexity resulted in the deposition of numerous sedimentary facies distributed among structural lows and highs, and their understanding is an essential aspect in order to reduce exploration risks. Therefore, the aims of this contribution are twofold: (a) to understand the depositional processes during the generation of the Itapema Formation coquina deposits in the offshore pre-salt Buzios Field, Santos Basin, and (b) to establish a depositional model and identify stacking patterns in the coquina section. The facies analysis was based on rock texture, structure, allochemical composition, taxonomic composition, and taphonomic characteristics of bivalve shells, such as fragmentation, abrasion, sorting, thickness, orientation, and articulation. We described 695 thin-sections and sidewall samples distributed among ten wells in the field area. The analysis resulted in sixteen facies grouped into eight facies associations: (1) bioclastic bars, (2) washover deposits, (3) backshore, (4) bioclastic beaches, (5) tempestites, (6) tempestites with articulated shells, (7) offshore and offshore transition deposits, and (8) offshore siliciclastic mudstones. These carbonate facies associations were deposited mainly under the influence of waves and currents in isolated ramp-shaped margined platforms with low continental input associated with active faults, characteristic of the rift phase of the basin evolution. The stacking of the facies associations indicates that the Itapema Formation coquinas were deposited in an environment that became progressively shallower towards the top contact with the overlying Barra Velha Formation. Siliciclastic mudstones mark the top of the Itapema Formation immediately below the Pre-Alagoas unconformity, indicating a significant lake deepening that drowned the coquina section. The depositional model is the first one about the Buzios Field and the first about the pre-salt fields coquinas based on field-scale information.

A New Species of <i>Nucleolites</i> (Echinoidea, Cassiduloida) from the Lower Albian of Russian Plate

A new species of Nucleolites from the Lower Albian deposits (Arcthoplites jachromensis Zone) of the Pavlovskoye section (Yuriev-Polsky district, Vladimir region) was described based on eight specimens. The species characterizes the late stages of the phylogeny of the genus and significantly expands its paleogeography. The taphonomic features of the burial made it possible to trace the structure of the jaw apparatus of the cassiduloid type in adult Nucleolites. For the first time in the Albian deposits of the Russian Plate, an extensive echinoderm assemblage, which is the most representative for the Lower Cretaceous deposits of the region as a whole, was established.

A FOSSIL FOREST FROM ITALY REVEALS THAT WETLAND CONIFERS THRIVED IN EARLY PERMIAN PERI-TETHYAN PANGEA

AbstractIn-situ fossil forests are valuable biogenic archives for the structure and setting of paleocommunities and the ecology of their organisms. Here, we present the first trees preserved in growth position in their embedding strata from the Kungurian (lower Permian) Athesian Volcanic Group, Northern Italy—one of the most extensive volcanic successions of post-Variscan Euramerica. We reconstruct the structure, rise and demise, and paleoecology of the forest based on high-resolution documentation of facies architectures and petrography, and the paleontological and taphonomic characters of the fossil content. Generally, the fossiliferous strata record a volcanotectonically controlled base-level rise in a limnic, possibly endorheic wetland basin from a low-relief volcanic landscape. The forest, preserved as calcified stem bases with roots, grew during a short interval of lake-level stasis on a small deltaic sheetflood fan. The forest comprised trees less than 5 m tall with tabular root systems adapted to the waterlogged substrate, and was buried and destroyed by mass flows following rapid submergence. These mass-flow deposits yield parautochthonous woody debris providing anatomical evidence of conifers as the major arborescent plants of the fossil forest. Our results not only elucidate the root architecture of Paleozoic conifers, but also document the ecomorphological plasticity of these plants and substantiate the presence of coniferopsids in wetlands around the Carboniferous/Permian boundary. Further, the evidence of lake perenniality in the studied succession is among the youngest known from the Permian of Europe, pointing to the highly differentiated late-icehouse impacts on continental environments in the Euramerican tropics.

Noteworthy Taphonomic Attributes of a Nautiloid Cephalopod from the Middle Silurian (Wenlock) Massie Formation of Southern Indiana

A specimen of the nautiloid cephalopod Dawsonoceras annulatum from the middle Silurian (Wenlock) Massie Formation of southeastern Indiana, USA, is herein described because of its suite of uncommon taphonomic characteristics. Three noteworthy features are observable. First, an articulated calymenid trilobite is preserved in the sediment infill of the cephalopod, having been either swept into the open shell post-mortem or rapidly buried alive while sheltering inside the hollow cavity. Second, a series of small (pinhole-sized) borings, potentially produced by ctenostomate bryozoans, are present on the upward-facing and lateral surfaces of the cephalopod shell, a feature that is otherwise unreported in this fauna. There appears to be a preference for boring into raised portions of the shell. Third, a number of tightly coiled microconchids are encrusting the exterior of the shell, an association not previously documented in this unit. Some of these phenomena represent first reports from a fossil fauna in a region strongly affected by dolomitization and are worthy of description on that basis alone. However, their co-occurrence on a single specimen highlights the fact that relatively common taxa such as cephalopods are still capable of yielding rare and/or significant taphonomic and paleoecological data.

Rhodolith-forming coralline red algae in the CaCO3 biofactory — A case study from the Serravallian of tropical northeastern Indian Ocean

Rhodolith-forming non-geniculate coralline red algae have been recorded from the Long Formation, exposed in four different outcrops at Little Andaman Island (Hut Bay) in the northeastern Indian Ocean. The non-geniculate corallines are represented by species of Sporolithon Heydrich, 1897, Mesophyllum Lemoine, 1928, Lithothamnion Heydrich, 1897, Phymatolithon Foslie, 1898, Lithoporella (Foslie) Foslie, 1909, Spongites Kützing, 1841, Neogoniolithon Setchell & Mason, 1943 and Lithophyllum Philippi, 1837. The algal assemblages also include geniculate corallines belonging to the genera Amphiroa Lamouroux, 1812 and Corallina Linnaeus, 1758. In addition, larger benthic foraminifers and few planktonic foraminifers also have been identified in thin section analysis. Based on the earlier study carried out on planktonic foraminifers, the Long Formation has been dated as Serravallian (late middle Miocene) and chronostratigraphically, the Long Formation has been included in the Ongeian Regional Stage. In the rhodolith-forming non-geniculate corallines, various growth forms and taphonomic features have been recognized. Diagenesis affected the studied material by micritization, cementation and compaction. The four outcrops are dominated by bioclastic wackestone and packstone composed of coralline red algae, benthic and planktonic foraminifers, echinoid spines and unidentified coral fragments. The rhodolith-forming coralline red algae, the growth forms and taphonomic features in non-geniculate corallines and the characteristic benthic foraminifers are indicative of a moderate energy depositional environment. This study indicates that the carbonate production was considerably high during the Serravallian of the tropical northeastern Indian Ocean.

Freshwater ecosystem collapse and mass mortalities at the Paleocene-Eocene thermal maximum

The Paleocene-Eocene thermal maximum (PETM), an abrupt global warming event linked to massive injections of carbon into the ocean-atmosphere system, was associated with large-scale deep-sea benthic extinction and major changes in planktonic ecosystems. However, due to the paucity of well-preserved fossils and high-resolution paleoenvironmental records, the PETM impacts on terrestrial ecosystems remain unclear. Here, we present geochemical and biological records of a lacustrine PETM section with exquisite fossils preserved from the Jianghan Basin, eastern China. Our data reveal the temporal relationship between carbon cycle perturbation, environmental changes, and biotic responses. Paleotemperatures derived from carbonate clumped isotope indicate a rapid increase by ~11 °C, synchronous with a negative carbon isotope excursion in organic matter and carbonates. Mass mortalities of terrestrial and aquatic animals were coincident with rapid warming during the PETM. Taphonomic features of animals, along with geochemical and sedimentological evidence, suggest that hyperthermal-induced toxigenic cyanobacterial blooms appear to be the most probable cause of the mass mortalities. Our findings expose a direct link between extreme warmth and increased probability of catastrophic ecological events in terrestrial ecosystems.

Histotaphonomy of a Pleistocene megamammal assemblage from Argentine Pampas

This work involves a multy-proxy approach of taphonomic features of the extinct giant ground sloth Lestodon armatus (Xenarthra, Mylodontidae). The study is based on paleohistological, mineralogical, and geochemical analyses from the Late Pleistocene Playa del Barco site (Buenos Aires Province, Argentina). Transverse thin sections of ribs and vertebrae were studied under light microscope, polarizing petrographic microscope, and scanning electron microscope (SEM), combined with chemical analysis using energy dispersive spectroscopy (EDS) and micro-X-ray diffraction (μXRD). The internal crystalline structure and mineral composition remains almost unaltered. The bone microstructure is well preserved in all the samples, although it was affected by different types of microfractures and infillings. Numerous radial microcracks were identified in the secondary osteons of all specimens evidencing wet depositional environment. The mineralogical and geochemical composition of the infillings and encrustations indicates that the enrichment with new elements was due to direct exchange with the sediments in which they were buried. Mineralogical evidence from the infillings allows to identify different diagenetic pathways; most of the skeletal elements were quickly buried in the vadose zone, while others were buried in the phreatic zone, directly or after some time immersed in a continental aquatic context. The fossildiagenetic information obtained from the Lestodon armatus fossils provides novel information to interpret and reconstruct the whole taphonomic history and the environmental and climatic conditions that favored the preservation of the Playa del Barco fossil assemblage during the end of the Last Glacial Maximum.

Taphonomy, paleoecology and chronology of a late Quaternary tank (natural reservoir) deposit from the Brazilian Intertropical Region

The Brazilian Intertropical Region (BIR) abounds with tank (natural reservoir) deposits, a primary source of late Quaternary megafauna remains. However, most of these important deposits lack comprehensive taphonomic analysis. In this study, we conducted a taphonomic analysis of Quaternary vertebrates from a specific tank deposit located at Fazenda Charco (Poço Redondo, Sergipe State), Brazil. We aimed to: (i) reconstruct the biostratinomic processes that influenced the deposition of vertebrate remains; (ii) interpret some fossildiagenetic features; and (iii) compare our findings with other tank deposits to highlight the main preservation patterns among these deposits. Additionally, we discuss the paleoenvironmental and paleoecological aspects of this vertebrate assemblage. The paleocommunity comprised eighteen individuals, including megamammals and reptiles, with a total of eleven taxa identified in the tank deposit, indicating a highly diversified assemblage. Eremotherium laurillardi and Toxodontinae indeterminate accounted for more than one individual each. Despite the high diversity, taphonomic features suggest the dominance of E. laurillardi in the assemblage and the preservation of bones transported from moderately distant locations to the tank deposit. Furthermore, Fazenda Charco exhibits a complex tank deposit characterized by various taphonomic signatures, including abrasion, trample marks, weathering, fragmentation, staining colors and bioerosions. These findings indicate that the bones underwent reworking events and were exposed to environmental conditions before their final burial. By integrating our taphonomic results with available isotopic, pollen, and speleothem data, we infer that a dry forest, resembling the extant Caatinga biome, prevailed during the past 42,000 years. This suggests a predominantly arid environment with a mosaic of phytophysiognomy dominated by herbs and shrubs. The further integration of taphonomic and paleoecological analyses of fossils from tank deposits will contribute to a more refined reconstruction of the paleoenvironmental scenario and the ecological interactions that occurred during the late Quaternary.

Taphonomy and dissolution rates of the razor clam Ensis magnus shells: Current status and projected acidification scenarios

The analysis of the natural variability of seawater (Ta, Ωaragonite and pCO2) at Rodas Beach (NW Iberian Peninsula, Spain) revealed an increase of acidification. However, such pH change was not linked to any detrimental effect of the shell taphonomic characteristics of live razor clams harvested during distinct temporal series (length, thickness, organic content or strength). Temperature affected negatively shell strength and thickness, although the large correlation between the environmental variables would limit the individual characterization. Modelled trends in pH (and Ωaragonite) showed a significant decrease in the last 20 years, despite Ω > 1. Therefore, more recent shells are being secreted in a progressively less saturated carbonate environment and, consequently, more prone to suffer dissolution (and weakening) in projected climatic scenarios. When shells of harvested razor clams were exposed to projected climatic scenarios in the laboratory, dissolution rates were significantly greater for cold-acidic scenarios (more corrosive) as compared to warm-acidic. The median dissolution time (DT50) for shells under the cold-acidic scenario was reduced by half (15 years) when compared to the values observed for shells under current water chemistry conditions (30 years).Galician coastline, often characterised by pCO2-rich and cold waters due to upwelling system, would represent the most corrosive scenario for the shells according to the responses monitored in our survey which highlight future compromise for the ecosystem services supplied by these hard skeletons. Future climate scenarios might condition performance of bivalves but also more complex processes related to carbonate structures. Local biodiversity may be lowered which may reduce the possibility that many species find shelter and feeding grounds, diminishing the optimal substrate for other organisms as needed elements for optimal services in the ecosystems.