Swiss ichthyosaurs: a review.

Switzerland is an ichthyosaur country: it has a rich record of marine reptile fossils, particularly the fish-shaped ichthyosaurs, and the according research. Here, we provide an overview over the 12 or more genera and at least 13 species plus numerous fragmentary remains of ichthyosaurs from the Triassic to the Cretaceous that have been discovered in twelve cantons thus far, of which four species are based on Swiss holotypes. This wealth of ichthyosaur species can be explained by their abundance in the Middle Triassic conservation deposits (Konservat Lagerstätte) of Monte San Giorgio, as well as occasional discoveries in strata of Middle Triassic to Early Cretaceous age. The moderate abundance of outcrops in reasonable conditions in combination with the long history of palaeontological research in Switzerland explains this good fossil record. In addition to this unique overview, we provide more data for further studies and update the knowledge of these taxa.

Lost, hidden, broken, cut-estimating and interpreting the shapes and masses of damaged assemblages of plesiosaur gastroliths.

Background: Gastroliths are stones of uncertain purpose that are commonly found inside the rib cages of plesiosaur fossils worldwide. Gastroliths from four Alberta (Canada) plesiosaurs were studied to determine both their shapes and masses, and their mass fractions relative to body mass. One animal's set of gastroliths was 100% complete and fully visible, but the others showed varying degrees of loss, damage or obscuration, so estimations of their original states were needed. Methods: The studied animals were: Albertonectes vanderveldei, Fluvionectes sloanae, Nichollssaura borealis and Wapuskanectes betsynichollsae. The animals come from three different palaeoenvironments: open marine, near shore marine, and fluvial. Gastrolith shapes were classified as either xiphoid, cylindrical, discoidal or spherical based on observed and/or estimated dimensions. Although not all methods could be applied in all cases, gastrolith shapes and masses were estimated four different ways: (1) direct measurement and weighing of a subset and predicting the properties of the remaining obscured and hidden stones; (2) measuring triaxial ellipsoid dimensions of free stones to calculate volumes and multiplying by the mass density of chert; (3) measuring two visible triaxial dimensions of embedded stones, estimating the hidden third dimension three different ways, and then determining volumes and masses by calculation; and (4) predicting the density and mass of a densely packed cluster of small gastroliths using geometrical arguments. Results: Total gastrolith mass never exceeded 0.2% of body mass in any plesiosaur, and is consistent with the idea that the amounts of gastroliths recovered with plesiosaurs would be ineffective as ballast. The largest plesiosaur in the sample had the largest single gastrolith and total gastrolith mass increases with body size. The shape characteristics of the gastroliths were different for different environments, but compositionally they are dominated by black cherts. A possible common source for the gastroliths was identified for the two geographically close and near-contemporanous Nichollssaura and Wapuskanectes.

Taphonomic impact of vertebrate scavengers on degradation and dispersal of remains, southeastern British Columbia.

Vertebrate scavengers represent important taphonomic agents that can act on a body, particularly when in an outdoor environment. Understanding the effects of these agents will direct how and where to search for human remains and influence the likelihood of discovery in a particular region. The current study aimed to identify the taphonomic impact of scavenger guilds in the peri-urban and rural regions of southeastern British Columbia. Vertebrate scavenger activity on pig carcasses was recorded remotely using trail cameras and analyzed to determine temporal scavenging profiles. Both the peri-urban and rural environments produced comparable scavenger guilds, namely: turkey vultures, American crows/northern ravens (classified as "corvids"), American black bears, and coyotes. Although the two locations had different study lengths due to variable degrees of scavenging, for the period that was common to both locations (summer to early fall), the black bear was the most frequent scavenger followed by coyote. However, the dispersal of remains by the mammalian scavengers was distinctly different between sites. Only 12%-33% of skeletal elements were recovered at the rural sites compared to 80%-90% recovered at the peri-urban sites, even though the latter sites had a longer study timeframe. The extended timeframe of the peri-urban sites confirmed that certain scavengers (e.g., turkey vultures and black bears) are only seasonally active in this region. These findings demonstrate the variability of scavenger behavior and the need to assign caution and local ecological knowledge when predicting scavenger trends. Such taphonomic information is relevant for human remains searches in regions with comparable scavenger guilds.

Forensic Anthropology in the identification of human remains found at sea: History of two judicial cases connected by the same marine context of discovery.

Background: Calculating the immersion time at sea of human skeletal remains is a challenge for forensic investigations and the answer to this question would solve many court cases in the shortest possible time. Remains in water create profound structural changes due to countless variables that lead to difficulties in interpretation during investigations. Case report: In this paper, two forensic cases found at sea were analysed, Case A, an extensively skeletonised corpse, and Case B, an isolated, intact foot with soft tissue, both found only 9 km away from the shores of the Tyrrhenian Sea (Southern Italy). A preliminary radiodiagnostic examination was performed for both cases. Subsequently, macroscopic observation of two tattoos found on case A was carried out. Autopsy examination was then carried out with subsequent anthropometric analysis to reconstruct the biological profile of both subjects, (case A) and (case B). Finally, histological and genetic analyses were performed. Conclusions: The examinations carried out made it possible to determine two compatible biological profiles, despite the taphonomic difference, and these examinations were corroborated by the anthropometric and genetic correlation, which led to the solution of a single judicial case. In conclusion, all the investigations carried out made it possible to state that the skeletonised corpse (Case A) and the isolated foot (Case B) belonged to the same individual in life. This result made it possible to identify the victim, thus establishing the profile of an individual who had disappeared in the previous two months due to a shipwreck.

Taxonomic and abundance biases affect the record of marine eukaryotic plankton communities in sediment DNA archives.

Environmental DNA (eDNA) preserved in marine sediments is increasingly being used to study past ecosystems. However, little is known about how accurately marine biodiversity is recorded in sediment eDNA archives, especially planktonic taxa. Here, we address this question by comparing eukaryotic diversity in 273 eDNA samples from three water depths and the surface sediments of 24 stations in the Nordic Seas. Analysis of 18S-V9 metabarcoding data reveals distinct eukaryotic assemblages between water and sediment eDNA. Only 40% of Amplicon Sequence Variants (ASVs) detected in water were also found in sediment eDNA. Remarkably, the ASVs shared between water and sediment accounted for 80% of total sequence reads suggesting that a large amount of plankton DNA is transported to the seafloor, predominantly from abundant phytoplankton taxa. However, not all plankton taxa were equally archived on the seafloor. The plankton DNA deposited in the sediments was dominated by diatoms and showed an underrepresentation of certain nano- and picoplankton taxa (Picozoa or Prymnesiophyceae). Our study offers the first insights into the patterns of plankton diversity recorded in sediment in relation to seasonality and spatial variability of environmental conditions in the Nordic Seas. Our results suggest that the genetic composition and structure of the plankton community vary considerably throughout the water column and differ from what accumulates in the sediment. Hence, the interpretation of sedimentary eDNA archives should take into account potential taxonomic and abundance biases when reconstructing past changes in marine biodiversity.

A mathematical description of fossilization.

Fossils constitute an inestimable archive of past life on the Earth. However, the stochastic processes driving decay and fossilization and overwhelmingly distorting this archive, are challenging to interpret. Consequently, concepts of exceptional or poor preservation are often subjective or arbitrarily defined. Here, we offer an alternative way to think about fossilization. We propose a mathematical description of decay and fossilization relying on the change in the relative frequency and characteristics of biogenic objects (e.g. atoms, functional groups, molecules, body parts and organisms) within an organism-fossil system. This description partitions taphonomic changes into three categories: gain, loss and alteration of state. Although the changes undergone by organisms through decay, preservation and alteration vary a lot for different organisms under different conditions, we provide a unified formalism which can be applied directly in the comparison of different assemblages, experiments and fossils. Our expression is closely related to George R. Price's famous equation for the change in evolutionary traits and can be adapted to the study of palaeontological systems and many others.

The effect of human decomposition on bullet examination.

Most firearm related homicides involve the deceased being forensically examined within a day or two, however, there are times when bodies have been examined and the fired components removed several days or weeks after death, when the body is in an active or advanced state of decomposition. In these cases, ballistic investigation has been found to be complicated due to the damage to the bullets, however the extent of this is not yet known. To date, there have been no studies investigating the effect of human decomposition and the subsequent analysis of bullets lodged in the body in an Australian context. Herein, seven fired copper jacketed bullets were manually inserted into three specific tissue types; lungs, abdomen and leg muscle (twenty-one bullets in total), of human donors in both cool and warm conditions at the Australian Facility for Taphonomic Experimental Research (AFTER). Bullets were removed every three days for a period of twenty-one days, and each bullet underwent manual microscopic examinations by firearms examiners across Australia. Results have indicated that the bullets corrode quickly in warm conditions, compared to bullets exposed to decomposition in cooler conditions. The results of this study will inform investigators and pathologists of the need to remove and examine fired bullets from decomposed bodies as soon as possible, especially in warm conditions to provide firearms examiners with the best opportunity to link fired bullets to a common source.

The effects of clays on bacterial community composition during arthropod decay.

Fossilization, or the transition of an organism from the biosphere to the geosphere, is a complex mechanism involving numerous biological and geological variables. Bacteria are one of the most significant biotic players to decompose organic matter in natural environments, early on during fossilization. However, bacterial processes are difficult to characterize as many different abiotic conditions can influence bacterial efficiency in degrading tissues. One potentially important variable is the composition and nature of the sediment on which a carcass is deposited after death. We experimentally examined this by decaying the marine shrimp Palaemon varians underwater on three different clay sediments. Samples were then analyzed using 16S ribosomal RNA sequencing to identify the bacterial communities associated with each clay system. Results show that samples decaying on the surface of kaolinite have a lower bacterial diversity than those decaying on the surface of bentonite and montmorillonite, which could explain the limited decay of carcasses deposited on this clay. However, this is not the only role played by kaolinite, as a greater proportion of gram-negative over gram-positive bacteria is observed in this system. Gram-positive bacteria are generally thought to be more efficient at recycling complex polysaccharides such as those forming the body walls of arthropods. This is the first experimental evidence of sediments shaping an entire bacterial community. Such interaction between sediments and bacteria might have contributed to arthropods' exquisite preservation and prevalence in kaolinite-rich Lagerstätten of the Cambrian Explosion. Supplementary Information: The online version contains supplementary material available at 10.1186/s13358-024-00324-7.

Histomorphometry specific to anthropological studies concerning the human condition.

Bone histomorphometry refers to the study of the structure and microscopic features of bone tissue. It involves the measurement and assessment of bone microanatomy, and it provides valuable information on bone properties. Through the application of histomorphometry, researchers can acquire information on bone metabolism and on remodeling dynamics, which is useful to the study of bone health. During the last 50 years, biological anthropologists have adopted the use of histomorphometry while examining issues specific to human health and evolutionary trends from prehistoric remains. Scientists coming from the medical field have applied histomorphometry in their research as it allows the study of bone changes, useful to describe pathological conditions among these ancient human remains. This paper reflects on some of the research that involves histomorphometric analysis specific to diet and health, forensic anthropology, taphonomic assessment of bone, non-human primate research and biomechanics. The purpose of the paper is to consider past and future applications of bone histomorphometry to enable a discussion which might direct research towards under-explored areas of bone biology. For example, looking at renewed interest in clavicular histology and stimulating investigations that focus on osteocyte density. Additionally, a discussion is offered concerning OPD values used to correlate chronological age to biological age estimations.

Late Ordovician eurypterid preserves oldest euchelicerate musculature in pyrite.

Pyritization of soft tissues of invertebrates is rare in the fossil record. In New York State, it occurs in black shales of the Lorraine Group (Late Ordovician), the best-known example of which is Beecher's Trilobite Bed. Exceptional preservation at the quarry where this bed is exposed allowed detailed examination of trilobite and ostracod soft-tissue anatomy. Here, we present the first example of a eurypterid (sea scorpion) currently ascribed to Carcinosomatidae from this deposit that also preserves the first evidence for mesosomal musculature in eurypterids. This specimen demonstrates that eurypterid musculature can be preserved in pyrite and evidences the oldest example of euchelicerate muscles within the fossil record. Sulfur isotope data illustrate that pyrite rapidly replicated muscle tissue in the early burial environment, prior to the pyritization of biomineralized exoskeleton and cuticular trilobite limbs. This discovery therefore expands the limited fossil record of euchelicerate musculature, while extending the taphonomic scope for preservation of detailed internal structures, more broadly, within arthropods.

Aquatic conditions & bacterial communities as drivers of the decomposition of submerged remains.

Aquatic decomposition, as a forensic discipline, has been largely under-investigated as a consequence of the highly complex and influential variability of the water environment. The limitation to the adaptability of scenario specific results justifies the necessity for experimental research to increase our understanding of the aquatic environment and the development of post-mortem submersion interval (PMSI) methods of estimation. This preliminary research aims to address this contextual gap by assessing the variation in the bacterial composition of aquatic biofilms as explained by water parameter measurements over time, associated with clothed and bare decomposing remains. As part of three field investigations, a total of 9 still-born piglets (n = 3, per trial) were used as human analogues and were submerged bare or clothed in either natural cotton or synthetic nylon. Changes in the bacterial community composition of the water surrounding the submerged remains were assessed at 4 discrete time points post submersion (7, 14, 21 and 28 days) by 16 S rRNA gene Next Generation Sequencing analysis and compared to coinciding water parameter measurements (i.e. conductivity, total dissolved solids (TDS), salinity, pH, and dissolved oxygen (DO)). Bacterial diversity was found to change over time and relative to clothing type, where significant variation was observed between synthetic nylon samples and bare/cotton samples. Seasonality was a major driver of bacterial diversity, where substantial variation was found between samples collected in early winter to those collected in mid - late winter. Water parameter measures of pH, salinity and DO were identified to best explain the global bacterial community composition and their corresponding dynamic trajectory patterns overtime. Further investigation into bacterial community dynamics in accordance with varying environmental conditions could potentially lead to the determination of influential extrinsic factors that may drive bacterial activity in aquatic decomposition. Together with the identification of potential bacterial markers that complement the different stages of decomposition, this may provide a future approach to PMSI estimations.

Anatomy and size of Megateuthis, the largest belemnite.

Belemnite rostra are very abundant in Mesozoic marine deposits in many regions. Despite this abundance, soft-tissue specimens of belemnites informing about anatomy and proportions of these coleoid cephalopods are extremely rare and limited to a few moderately large genera like Passaloteuthis and Hibolithes. For all other genera, we can make inferences on their body proportions and body as well as mantle length by extrapolating from complete material. We collected data of the proportions of the hard parts of some Jurassic belemnites in order to learn about shared characteristics in their gross anatomy. This knowledge is then applied to the Bajocian genus Megateuthis, which is the largest known belemnite genus worldwide. Our results provide simple ratios that can be used to estimate belemnite body size, where only the rostrum is known.

Utilization of qPCR to Determine Duration and Environmental Drivers Contributing to the Persistence of Human DNA in Soil.

Little is known about the underlying mechanisms that contribute to the persistence and degradation of DNA within soil. The goals of this study are to determine the duration of mitochondrial DNA (mtDNA) and nuclear DNA (nuDNA) persistence in soils enriched by surface-level human decomposition and to better understand the contribution of environmental factors. The surface-level decomposition of three human cadavers was documented over 11 weeks. Based on quantitative PCR results, we found nuDNA to persist in soils six weeks post-placement, while mtDNA was recoverable for the entire 11-week decomposition period. Principle components analyses and Spearman's rank correlations revealed that (1) time, (2) total body score, and (3) weekly average air temperature were significantly correlated with concentrations of nuDNA and mtDNA in soil, suggesting these factors play a role in the degradation of DNA in soils.

Comparison of the effectiveness and efficiency of the grid and link search methods to recover scattered skeletal remains.

The grid and link search methods are used to recover scattered skeletal remains. Neither have not been compared robustly and clear guidelines for the link method have not been sufficiently developed. The study aimed to compare the effectiveness and efficiency of both methods and propose guidelines for the link method. The scattering patterns of two scavengers of forensic relevance-slender mongooses (Galerella sanguinea) and black-backed jackals (Canis mesomelas)-were recreated using four pig skeletons (Sus scrofa domesticus). Two groups (n = 6 each) were assigned a different method to recover the scattered remains. The length of the search and when each bone was located for each scatter pattern was recorded for each group and scatter pattern. A Likert scale questionnaire assessed participants' perceptions of their assigned method. A paired t-test (p = 0.005) compared the efficiency of each method and the questionnaire answers. Both methods were effective, recovering 100% of all remains. The link method was more efficient for both scatter patterns, despite there being no statistical significance (jackal: p = 0.089; mongoose: p = 0.464). Participants indicated favorable views for both methods; however, the link method scored significantly more favorably (p = 0.01) for efficiency. Specific guidelines were developed for the use of the link method. The link method is suggested for the recovery of scattered remains in forensic contexts, especially when the scavenger, its behavior, and scattering pattern is known or suspected.

The influence of rehydration on decomposition in the Highveld region of South Africa-Using a pig model.

Researchers have observed that rainfall may re-initiate decomposition in desiccated tissue; however, no conclusive research-based evidence exists on the specific effects of rehydration on decomposition. Therefore, this study aimed to assess the effects of artificial rehydration on the progression of decomposition following the advanced stage of decomposition. Twelve adult pig cadavers (8 experimental; 4 controls) were placed in the central Highveld of South Africa during cooler (April-July 2021) and warmer (August-November 2021) months. Decomposition was scored approximately biweekly to obtain the total body score, and accumulated degree days (ADD) were calculated for each pig. All pig cadavers were covered by chicken wire cages with transparent tarps to control for natural rehydration and scavenging. Once the experimental pig cadavers reached a three-visit stasis in the advanced phase of decomposition, they were artificially rehydrated, and changes in the progression of decomposition between the control and experimental groups were plotted (ADD against TBS) for observation. The rehydrated experimental pig cadavers showed re-initiation of decay and insect re-colonization, while the control cadavers mainly remained in a state of stasis with insect activity ceased altogether. Greater cadaver decomposition islands and a color change post-rehydration were also noted in some experimental cadavers. This supports the need for future research on the impact of rehydration, including associated soil moisture on decomposition rates, progression, and invertebrate colonization, which will enhance our understanding of the effects these environmental factors have on the accuracy of post-mortem interval estimation.

Volatile organic compounds produced during postmortem processes can be linked via chromatographic profiles to individual postmortem bacterial species.

Decomposition odor is produced during postmortem mammalian tissue breakdown by bacteria, insects, and intrinsic chemical processes. Past research has not thoroughly investigated which volatile organic compounds (VOCs) can be linked directly to individual bacterial species on decomposing remains. The purpose of this study was to profile the VOCs produced over time by individual species of bacteria using comprehensive two-dimensional gas chromatography (GC×GC) to expand our foundational knowledge of what each bacterial species contributes to decomposition odor. Five different species of bacteria (Bacillus subtilis, Ignatzschineria indica, Ignatzschineria ureiclastica, Curtobacterium luteum, and Vagococcus lutrae) were cultured on standard nutrient agar individually and monitored daily using solid phase microextraction arrow (SPME Arrow) and GC×GC in combination with quadrupole mass spectrometry (qMS) and flame ionization detection (FID). The GC×GC-qMS/FID approach was used to generate rich VOC profiles that represented the bacterial species' metabolic VOC production longitudinally. The data obtained from the chromatographic output was used to compare with a prior study using one-dimensional GC-qMS, and also between each of the five species to investigate the extent of overlap between species. No single VOC could be found in all five bacterial species investigated, and there was little overlap in the profile between species. To further visualize these differences, chromatographic peak data was investigated using two different ordination strategies, principal component analysis (PCA) and principal coordinate analysis (PCoA). The two ordination strategies were compared with each other using a Procrustes analysis. This was performed to understand differences in ordination strategies between the separation science community and chemical ecological community. Overall, ordination strategies were found to produce similar results, as evidenced by the correlation of PCA and PCoA in the Procrustes analysis. All analysis strategies yielded distinct VOC profiles for each species. Further study of additional species will support understanding of the holistic view of decomposition odor from a chemical ecology perspective, and further support our understanding of the production of decomposition odor that culminates from such a complex environment.

The taphonomic effects of long-term burial in the South African Highveld.

Taphonomy studies the environmental effects on remains from the time of deposition to the time of recovery and has been integrated into the field of forensic anthropology. The changes to skeletal remains are dependent on the method of disposal and the surrounding environment. This study focused on buried remains where the type and chemical composition of the soil and the microorganisms present need to be considered. The aim was to investigate the type, frequency, and correlations of the taphonomic alterations of buried domestic pigs. Six taphonomic alterations were observed which included depositional staining, adipocere formation, bone weathering, acidic soil corrosion, and plant, and animal activity. Depositional staining, weathering and plant activity were the most common alterations followed by adipocere which was present on 92.3% of the remains. The bones were mostly stained dark brown and brown; however, the trunk region was the only region to present with black staining. The right sides were darker than the left due to the body positioning as most pigs were placed on their right sides and thus were in direct contact with the cadaver decomposition island. Additionally, the right sides presented with more adipocere as well as increased plant activity suggesting that the soil retained water. Darker stains were correlated with a more complete skeleton as adipocere provides some protection. The study confirms that there are various complicated relationships between different taphonomic alterations. A good understanding of them is needed in forensic anthropology to assist in reconstructing the events that occur after death.

Examining cut mark residue with SEM to identify metal tool use: An experimental study.

In this manuscript, we explore the potential of studying metal residues in cut marks generated by copper and bronze knives. The method was developed in the forensic sciences for use with modern metals in order to identify microscopic particles of metal tools on bone surfaces. However, the study of residues in archaeological materials can be challenging due to the ways in which the bone remains may have been manipulated, both in the past and in more recent times. Using a scanning electron microscope (SEM), we detected microscopic fragments of bronze and copper knives along with contamination both inside and outside of the cut marks made by those knives. Copper and bronze residues were identified embedded in the bone inside the incisions and, in two cases, they left greenish stains caused by metal oxidation. In contrast, modern contamination of undetermined origin was found unattached to the bone and had a chemical composition not compatible with that of the knives. The amount of residue was influenced by the quantity of soft tissue between the bone and the knife during the butchering tasks. Bone cooking does not seem to influence the preservation of the residues. We anticipate that the approach used in this first exploratory study will emerge as a promising method for identifying the use of metal tools in archaeological bone remains.

The marine conservation deposits of Monte San Giorgio (Switzerland, Italy): the prototype of Triassic black shale Lagerstätten.

Marine conservation deposits ('Konservat-Lagerstätten') are characterized by their mode of fossil preservation, faunal composition and sedimentary facies. Here, we review these characteristics with respect to the famous conservation deposit of the Besano Formation (formerly Grenzbitumenzone; including the Anisian-Ladinian boundary), and the successively younger fossil-bearing units Cava inferiore, Cava superiore, Cassina beds and the Kalkschieferzone of Monte San Giorgio (Switzerland and Italy). We compare these units to a selection of important black shale-type Lagerstätten of the global Phanerozoic plus the Ediacaran in order to detect commonalities in their facies, genesis, and fossil content using principal component and hierarchical cluster analyses. Further, we put the Monte San Giorgio type Fossillagerstätten into the context of other comparable Triassic deposits worldwide based on their fossil content. The results of the principal component and cluster analyses allow a subdivision of the 45 analysed Lagerstätten into four groups, for which we suggest the use of the corresponding pioneering localities: Burgess type for the early Palaeozoic black shales, Monte San Giorgio type for the Triassic black shales, Holzmaden type for the pyrite-rich black shales and Solnhofen type for platy limestones.

Human brains preserve in diverse environments for at least 12 000 years.

The brain is thought to be among the first human organs to decompose after death. The discovery of brains preserved in the archaeological record is therefore regarded as unusual. Although mechanisms such as dehydration, freezing, saponification, and tanning are known to allow for the preservation of the brain on short time scales in association with other soft tissues (≲4000 years), discoveries of older brains, especially in the absence of other soft tissues, are rare. Here, we collated an archive of more than 4400 human brains preserved in the archaeological record across approximately 12 000 years, more than 1300 of which constitute the only soft tissue preserved amongst otherwise skeletonized remains. We found that brains of this type persist on time scales exceeding those preserved by other means, which suggests an unknown mechanism may be responsible for preservation particular to the central nervous system. The untapped archive of preserved ancient brains represents an opportunity for bioarchaeological studies of human evolution, health and disease.