Fossil Research Articles

A new biomechanical approach to cranial suture function: the role of contact elements in linear and nonlinear models

Abstract Understanding cranial sutures and how they relieve and dissipate stress is essential to assess their role in cranial biomechanics and to develop highly accurate predictive models. This involves examining how ontogeny affects cranial sutures, as well as their morphology and function, and how these changes through time may impact essential biomechanical loadings such as chewing or direct biting. In this work, we study the cranial sutures of Crocodylus niloticus in detail using contact elements under finite element analysis. Contact elements permit the creation of a physical relationship between two bones that are in contact and even the configuration of these relationships, for example, in terms of movement or flexibility. The definition of bone contacts may require linear and/or nonlinear computational solutions to attain higher accuracy. Herein, skull geometry is tested to determine how bones may be altered by different types of contacts under various conditions. As predicted, the absence of sutures or cranial kinesis leads to a reduction in stress distribution across the skull, whereas sutures and cranial kinesis help the skull relieve stress and prevent certain bones from sustaining high stress levels. The type of contact used in individual sutures has a significant effect on model outcomes. Additionally, feeding behaviors significantly impact cranial biomechanics, reflecting the influence of other variables that may be applied to the models. As highlighted by the results, in order to obtain accurate results when analyzing fossil taxa, the nature of the cranial sutures should be taken into account. Therefore, developing predictive models based on living taxa is invaluable, because it facilitates the study of extinct taxa for which there is a lack of information on the fibrous joints due to poor or no preservation in the fossil record.

Investigating the Timing of Carbonate Precipitations and Their Potential Impact on Fossil Preservation in the Hell Creek Formation

Because fossilized skeletal remains and enclosing sedimentary rocks experience similar diagenetic conditions (i.e., temperature, pressure, and pore fluid interaction,) enclosing sedimentary rocks may provide insight into bone diagenesis. A fossil assemblage, including in situ dinosaur fossils, was discovered in Makoshika State Park near Glendive, MT. Fossil-bearing sandstone is a crevasse splay deposit, and fossils show no sorting or preferred orientation. Bone-bearing sandstone exhibits evidence for intense diagenesis, suggesting a maximum temperature of ~90 °C. Concretion associated with fossils includes two distinctive matrices: dark- and light-colored matrices. Another concretion was found in channel sandstone near the base of the outcrop. These carbonate phases have distinctive isotopic compositions; δ13C values for dark-colored matrices, light-colored matrices, and spheroidal concretion are −7.5, 2.1, and −22.4‰ (VPDB), respectively, and their δ18O values are 16.4, 25.9, and 17.8‰ (VSMOW), respectively. In contrast, fossilized bone δ13C and δ18O values were −4.4‰ (VPDB) and 20.6‰ (VSMOW), respectively, suggesting fractionation with pore fluid was limited. Early carbonate precipitation evidenced by grain coating may have reduced interaction between pore fluids and fossils. Although concretion formation and permineralization do not appear to directly aid in fossil preservation, concretions preserve valuable evidence for diagenetic history.

Extremely rapid, yet noncatastrophic, preservation of the flattened-feathered and 3D dinosaurs of the Early Cretaceous of China

Northeast China's Early Cretaceous Yixian Formation preserves spectacular fossils that have proved extraordinarily important in testing evolutionary hypotheses involving the origin of birds and the distribution of feathers among nonavian dinosaurs. These fossils occur either flattened with soft tissue preservation (including feathers and color) in laminated lacustrine strata or as three-dimensional (3D) skeletons in "life-like" postures in more massive deposits. The relationships of these deposits to each other, their absolute ages, and the origin of the extraordinary fossil preservation have been vigorously debated for nearly a half century, with the prevailing view being that preservation was linked to violent volcanic eruptions or lahars, similar to processes that preserved human remains at Pompeii. We present high-precision zircon U-Pb geochronology from cores and outcrops, demonstrating that Yixian Formation accumulation rates are more than an order of magnitude higher than usually estimated. Additionally, we provide zircon provenance and sedimentological data from 3D dinosaur fossils, which imply that their death and burial occurred in collapsed burrows, rather than via a catastrophic volcanogenic mechanism. In the studied area, the three principal fossil-rich intervals of the Yixian occur as a cyclic sequence that correspond to periods of high precipitation. Using Bayesian-Markov Chain Monte Carlo approaches, we constrain the total duration of the sequence to less than ~93,000 y and suggest that climatic precession paced the expression of these cyclic sediments. Rather than representing multiple, Pompeii-like catastrophes, the Yixian Formation is instead a brief snapshot of normal life and death in an Early Cretaceous continental community.

Uncovering the relationships among herring-like fossils (Clupei: Teleostei): a phylogenetic analysis

Abstract Research interest in the diversity and evolutionary history of herring-like fossils (subcohort Clupei) has increased in recent decades. However, little is known about the relationships between fossils assigned to Clupei, particularly those that are demonstrably related to extant herring-like members of the order Clupeiformes. To help bridge this gap, we present a new morphological phylogeny that includes representatives of all major clupeiform lineages. The data matrix consists of 192 characters, drawn from 79 extant and 37 fossil taxa and selected to be readily identifiable in fossils. Most clupeiform families are recovered as monophyletic, and their interrelationships are generally compatible with previous morphological hypotheses. The phylogenetic positions of six fossil clupeiform taxa are resolved, as the results of all analyses (unconstrained/constrained parsimony and Bayesian inference) are consistent. Twenty-one fossil taxa are incertae sedis, including two species of Ellimmichtyiformes, which are recovered as Clupeoidei in the parsimony analyses. The relationships of the rest of the fossils are interpreted with varying degrees of certainty. The evolution of key morphological characters is discussed in light of the new results, and four fossil taxa are proposed as calibration points for future dating studies.

Magnetostratigraphic and Sedimentological Insights into the Late Campanian Uberaba Formation of the Bauru Group, Southeast Brazil

The Uberaba Formation, a significant paleontological site within the Bauru Group, was deposited over the Early Cretaceous volcanic rocks of the Paraná Basin in southern Brazil. It occupies a restricted northeastern area of the basin surrounding the homonymous city. Recent works on stratigraphy and paleontology indicate a Campanian age, a novel finding that challenges the previously held belief of a Cenomanian age based on dinosaur bones. Paleomagnetic work on seven sections of the Uberaba formation has resulted in the calculation of a paleomagnetic pole at 82.2 ºS 350.8 ºE (N = 89; k = 23; A95 = 3.2º) after correcting for the shallowing of the magnetic inclination caused by overload. The formation is dated to ∼73 Ma (Campanian) age based on magnetostratigraphic data and comparisons with other Late Cretaceous poles. This age implies an interval of about 40 Myr separates the deposition of the Uberaba and Caiuá formations– the latter being the first post-magmatic sedimentation in the Paraná Basin. The area stayed as a highland until the tectonic events related to the northward emplacement of the alkaline provinces. High deposition rates were determined, at least for the upper part of the formation, based on the magnetostratigraphic characteristics.

The Micropaleoecology Framework: Evaluating Biotic Responses to Global Change Through Paleoproxy, Microfossil, and Ecological Data Integration.

The microfossil record contains abundant, diverse, and well-preserved fossils spanning multiple trophic levels from primary producers to apex predators. In addition, microfossils often constitute and are preserved in high abundances alongside continuous high-resolution geochemical proxy records. These characteristics mean that microfossils can provide valuable context for understanding the modern climate and biodiversity crises by allowing for the interrogation of spatiotemporal scales well beyond what is available in neo-ecological research. Here, we formalize a research framework of "micropaleoecology," which builds on a holistic understanding of global change from the environment to ecosystem level. Location: Global. Time period: Neoproterozoic-Phanerozoic. Taxa studied: Fossilizing organisms/molecules. Our framework seeks to integrate geochemical proxy records with microfossil records and metrics, and draws on mechanistic models and systems-level statistical analyses to integrate disparate records. Using multiple proxies and mechanistic mathematical frameworks extends analysis beyond traditional correlation-based studies of paleoecological associations and builds a greater understanding of past ecosystem dynamics. The goal of micropaleoecology is to investigate how environmental changes impact the component and emergent properties of ecosystems through the integration of multi-trophic level body fossil records (primarily using microfossils, and incorporating additional macrofossil data where possible) with contemporaneous environmental (biogeochemical, geochemical, and sedimentological) records. Micropaleoecology, with its focus on integrating ecological metrics within the context of paleontological records, facilitates a deeper understanding of the response of ecosystems across time and space to better prepare for a future Earth under threat from anthropogenic climate change.

First fossil evidence of an extinct malvalean genus from India

ABSTRACT Hither, an extinct floral element of Florissantia Knowlton, unearthed from the early Eocene (~55–52 Ma) of the Gurha lignite mine, Rajasthan, western India, aids in highlighting the evolutionary significance of this angiosperm lineage in the Indian Cenozoic history. Comparison with fossil taxa from other regions supports the attribution to an extinct malvalean genus Florissantia. It is characterized by a transversely impressed, actinomorphic, gamosepalous flower with five rounded lobed sepals, each sepal fused at least 60% of its length, sinuses between sepal lobes shallowly incised and radiating reticulate venation. The occurrence of this extinct genus, previously known only from the Paleogene of North America and East Asia, is pertinent to the malvalean floristic diversification in India.

Geochemical characterization of trace fossil assemblages in spotted marls and limestones of the Lower Jurassic of the Western Carpathians: environmental implications

AbstractThe trace fossils of the spotted limestones and marls from upper Pliensbachian of the Skladaná Skala section, Western Carpathians (Slovakia), are characteristic of Zoophycos ichnofacies preserved in outer shelf deposits. The ichnoassociation is dominated by Lamellaeichnus and Chondrites, while Palaeophycus, Planolites, Teichichnus, Thalassinoides, Trichichnus, and Zoophycos, are less abundant. The presence of relatively large sized traces (reaching a decimetre in horizontal dimension for Thalassinoides and Zoophycos) and continuously well bioturbated deposits point to well oxygenated shallow zone (mixed layer) and deeper part of stiffed substrate of the transitional layer of bottom substrate up to the first tens of centimetres to depth. A first tier (tier I) corresponds to the shallowest sediment occupied by Bathysiphon tests and other epifaunal body fossils. The tier II is characterized by shallow infaunal burrows of deposit feeders (Planolites) and permanent dwelling, open burrows (Palaeophycus, Thalassinoides) located in a Ca-rich sediment (corresponding to CaCO3). The tier III is dominated by deposit feeders (Lamellaeichnus, Teichichnus) that burrowed stiff Ca-rich sediment below the redox boundary. Trace fossils of tier III are rich in fine siliciclastics (high content in Si, Al, K mainly associated to clays) and pyrite framboids (enrichment in Fe, S and Co). The deposit-feeders of tier III maintain connection to the sediment-water interface. Tier IV (Zoophycos, Teichichnus and large Chondrites), and deepest infaunal forms of the tier V. (Trichichnus, Pilichnus and tiny forms of Chondrites) comprises trace fossils commonly rich in pyrite framboids with relatively high content of Fe, S, and Co, congruent with chemosymbiotic behaviour commonly inferred for Chondrites, Trichichnus, and the organic-matter storage of Zoophycos.

Parallel evolution of unusual ‘harpiform’ morphologies in distantly related trilobites

Abstract Harpetid and trinucleid trilobites share a similar and unusual morphology, the most striking feature of which is a wide, flattened cephalic brim with many pits or holes. This similarity was once interpreted as a sign that these two groups of trilobites were closely related, but in recent years it has instead been assumed that the ‘harpiform’ brim arose in both groups independently. However, relatedness and similarity can be difficult to disentangle in fossil taxa without close living relatives, and this assumption about the harpiform brim has never been explicitly tested. Our study re-evaluates the relationship between Harpetida and Trinucleioidea in order to test a longstanding assumption about trilobite relationships and as a case study in evaluating different kinds of morphological similarity in extinct groups. We inferred a new phylogenetic tree using parsimony methods and discrete morphological character data from a broad sampling of harpetids, trinucleids, and their relatives. Despite their gross morphological similarities, we found that harpetids and trinucleids were readily distinguished in our analyses, a result consistent with a hypothesis of multiple origins for the harpiform brim. By mapping brim-related characters across our new phylogeny, we identified a sequence of morphological innovations that arose in parallel in both groups and led ultimately in each case to the evolution of the harpiform brim. These results indicate that harpiform brims are a prime example of parallel evolution—the similar development of a morphological trait in distantly related taxa that nevertheless share a similar original morphology. In addition, our phylogeny supports the idea that trinucleids are specialized, harpiform asaphids, rather than an independent order of trilobites. We also provide new information on the relationships of the putative ‘basal-most’ members of Trinucleioidea, the Liostracinidae, and confirm recent assessments that this family is more distantly related to trinucleids.

Assessing the Adequacy of Morphological Models using Posterior Predictive Simulations.

Reconstructing the evolutionary history of different groups of organisms provides insight into how life originated and diversified on Earth. Phylogenetic trees are commonly used to estimate this evolutionary history. Within Bayesian phylogenetics a major step in estimating a tree is in choosing an appropriate model of character evolution. While the most common character data used is molecular sequence data, morphological data remains a vital source of information. The use of morphological characters allows for the incorporation fossil taxa, and despite advances in molecular sequencing, continues to play a significant role in neontology. Moreover, it is the main data source that allows us to unite extinct and extant taxa directly under the same generating process. We therefore require suitable models of morphological character evolution, the most common being the Mk Lewis model. While it is frequently used in both palaeobiology and neontology, it is not known whether the simple Mk substitution model, or any extensions to it, provide a sufficiently good description of the process of morphological evolution. In this study we investigate the impact of different morphological models on empirical tetrapod data sets. Specifically, we compare unpartitioned Mk models with those where characters are partitioned by the number of observed states, both with and without allowing for rate variation across sites and accounting for ascertainment bias. We show that the choice of substitution model has an impact on both topology and branch lengths, highlighting the importance of model choice. Through simulations, we validate the use of the model adequacy approach, posterior predictive simulations, for choosing an appropriate model. Additionally, we compare the performance of model adequacy with Bayesian model selection. We demonstrate how model selection approaches based on marginal likelihoods are not appropriate for choosing between models with partition schemes that vary in character state space (i.e., that vary in Q-matrix state size). Using posterior predictive simulations, we found that current variations of the Mk model are often performing adequately in capturing the evolutionary dynamics that generated our data. We do not find any preference for a particular model extension across multiple data sets, indicating that there is no 'one size fits all' when it comes to morphological data and that careful consideration should be given to choosing models of discrete character evolution. By using suitable models of character evolution, we can increase our confidence in our phylogenetic estimates, which should in turn allow us to gain more accurate insights into the evolutionary history of both extinct and extant taxa.

Temporal lobe evolution in Hominidae and the origin of human lobe proportions.

Objectives Evolutionary changes in hominin social complexity have been associated with increases in absolute brain size. The temporal lobes are nestled in the middle cranial fossae (MCF) of the skull, the dimensions of which allow estimation of temporal lobe volume (TLV) in extant and fossil taxa. Materials and Methods The main aim of this study is to determine where along the hominid phylogeny, major temporal lobe size transitions occurred. We used computed tomography (CT) scans of crania, 3D photogrammetry data, and laser surface scans of endocranial casts to measure seven MCF metrics in 11 extant anthropoid taxa using multiple regressions to estimate TLV in 5 extant hominids and 10 fossil hominins. Phylogenetic comparative methods mapped temporal lobe size, brain size, and temporal lobe proportions onto phylogenetic trees broadly for Hominidae and specifically for Hominini. Results Extant Homo sapiens were not an outlier in relative brain size, temporal lobe size, or proportions of the temporal lobes, but some proportions within the lobe were uniquely altered. The most notable changes in relative temporal lobe size and proportions saw a decrease in relative temporal lobe size and proportions in the genus Pan compared to other extant great apes and fossil hominins while there was a relative increase in the temporal lobe width and length in Australopithecus-Paranthropus clade compared to the genus Homo and other extant great apes including modern humans. Discussion We do not find support for the social brain, environmental or functional craniology hypotheses alone but think it prudent to consider the implications of cerebral reorganization between the temporal lobes and other regions of the brain within the context of these hypotheses and with future investigation is warranted.

A New Technique for Age Assessment of Ancient Bones by Using Cr-39 Track Detector

A new highly sensitive technique is proposed to estimate the age of ancient bones by the specific activity of 226Ra, which is determined by the registration of 222Rn α–particles using a CR-39 track detector in an isolated chamber. Comparison of specific activity of 226Ra in the bones of archanthropus, southern mammoths, and dinosaurs between standard bones showed that there is a direct correlation between age and specific activity of 226Ra in these bones. The work also shows the specific activity of 226Ra in soils taken from the sites of detection of the studied skeletons.

Chronology of Ediacaran sedimentary and biogeochemical shifts along eastern Gondwanan margins

Determining causal relationships between environmental change and early animal evolution has been limited by our lack of a robust temporal framework for the Ediacaran Period (635-539 million years ago). Here we present six new radioisotopic age constraints from the Sultanate of Oman, which furnish a quantitative temporal framework for biogeochemical changes associated with animal radiation in the middle and late Ediacaran Period. In addition to constraining the duration of Earth’s largest negative carbon isotope excursion in its type locality, this temporal framework underpins a new understanding of Ediacaran sedimentation rates, a critical control on geochemical records and fossil preservation. Our new dates quantify early Ediacaran (prior to c. 574 million years ago) condensation in key sections across Gondwanan margins. This temporal framework highlights a pressing need to reassess proxy records of oxygenation—often hypothesized as a critical environmental constraint for the emergence of complex multicellular life—considering non-static sedimentation rates.

Early Pennsylvanian Lagerstätte reveals a diverse ecosystem on a subhumid, alluvial fan

Much of what we know about terrestrial life during the Carboniferous Period comes from Middle Pennsylvanian (~315–307 Mya) Coal Measures deposited in low-lying wetland environments1–5. We know relatively little about terrestrial ecosystems from the Early Pennsylvanian, which was a critical interval for the diversification of insects, arachnids, tetrapods, and seed plants6–10. Here we report a diverse Early Pennsylvanian trace and body fossil Lagerstätte (~320–318 Mya) from the Wamsutta Formation of eastern North America, distinct from coal-bearing deposits, preserved in clastic substrates within basin margin conglomerates. The exceptionally preserved trace fossils and body fossils document a range of vertebrates, invertebrates and plant taxa (n = 131), with 83 distinct foliage morphotypes. Plant-insect interactions include what may be the earliest evidence of insect oviposition. This site expands our knowledge of early terrestrial ecosystems and organismal interactions and provides ground truth for future phylogenetic reconstructions of key plant, arthropod, and vertebrate groups.

Biomolecules in Pleistocene fossils from tropical cave indicate fossil biofilm

Finding biomolecules in fossils is a challenging task due to their degradation over time from physical, chemical, and biological factors. The primary hypothesis for explaining the presence of biomolecules in fossilized bones tissues suggests their survival in the fossilization process. In contrast, some of these biomolecules could either derive from bacteria biofilm, thus without a direct relationship with the fossil record or could be an artifact from measurement procedures. Raman spectroscopy studies across various fossil ages and environments have detected multiple bands ranging from 1200 to 1800 cm−1 associative of organic compounds. However, the significance of these bands remains elusive. Our research aims to address this issue through a deep Raman spectroscopy investigation on Pleistocene teeth from Tayassu and Smilodon populator. These fossils were obtained from a well-preserved stratigraphic succession in Toca de Cima do Pilão cave, near the National Park of Serra da Capivara in semiarid Brazil. We propose two hypotheses to explain the presence of organic compounds related to 1200 to 1800 cm−1 Raman spectral range in fossil tissues: (i) these bands are biological signatures of preserved fossil biomolecules, or (ii) they are exogenous biological signatures associated with the bacterial biofilm formation during post-depositional processes. Our results align with the latter hypothesis, followed by biofilm degradation. However, the specific mechanisms involved in the natural biofilm degradation in fossil records remain unexplored in this study. In our case, the formation of biofilm on fossil bones is attributed to the oligotrophic conditions of the cave sediment matrix. We present a comprehensive model to elucidate the existence of biofilm on fossilized tissues, emphasizing the pivotal role of post-depositional processes, especially water action, in the cave environment. As the fossils were discovered in a cave setting, post-depositional processes significantly contribute to the formation of the biofilm matrix. Although our study provides insights into biofilm formation, further research is needed to delve into the specific mechanisms driving natural biofilm degradation in fossils.

Why animals construct helical burrows: Construction vs. post-construction benefits.

The extended phenotype of helical burrowing behavior in animals has evolved independently many times since the Cambrian explosion (~540 million years ago [MYA]). A number of hypotheses have been proposed to explain the evolution of helical burrowing in certain taxa, but no study has searched for a general explanation encompassing all taxa. We reviewed helical burrowing in both extant and extinct animals and from the trace fossil record and compiled 10 hypotheses for why animals construct helical burrows, including our own ideas. Of these, six are post-construction hypotheses-benefits to the creator or offspring, realized after burrow construction-and four are construction hypotheses reflecting direct benefits to the creator during construction. We examine the fit of these hypotheses to a total of 21 extant taxa and ichnotaxa representing 59-184 possible species. Only two hypotheses, antipredator and biomechanical advantage, cannot be rejected for any species (possible in 100% of taxa), but six of the hypotheses cannot be rejected for most species (possible in 86%-100% of taxa): microclimate buffer, reduced falling sediment (soil), anticrowding, and vertical patch. Four of these six are construction hypotheses, raising the possibility that helical burrowing may have evolved without providing post-construction benefits. Our analysis shows that increased drainage, deposit feeding, microbial farming, and offspring escape cannot explain helical burrowing behavior in the majority of taxa (5%-48%). Overall, the evidence does not support a general explanation for the evolution of helical burrowing in animals. The function and evolution of the helix as an extended phenotype seems to provide different advantages for different taxa in different environments under different physicochemical controls (some traces/tracemakers are discussed in more detail due to their association with body fossils and well-constrained physicochemical parameters). Although direct tests of many of the hypotheses would be difficult, we nevertheless offer ways to test some of the hypotheses for selected taxa.

A Biofilm Channel Origin for Vermiform Microstructure in Carbonate Microbialites.

A three-dimensional tubular fabric known as "vermiform microstructure" in Phanerozoic and Neoproterozoic carbonate microbialites has been hypothesized to represent the body fossil of nonspicular keratose demosponges. If correct, this interpretation extends the sponge body fossil record and origin of animals to ~890 Ma. However, the veracity of the keratose sponge interpretation for vermiform microstructure remains in question, and the origin of the tubular fabric is enigmatic. Here we compare exceptionally well-preserved microbialite textures from the Upper Triassic to channel networks created by modern microbial biofilms. We demonstrate that anastomosing channel networks of similar size and geometries are produced by microbial biofilms in the absence of sponges, suggesting the origin for vermiform microstructure in ancient carbonates is not unique to sponges and perhaps best interpreted conservatively as likely microbial in origin. We present a taphonomic model of early biofilm lithification in seawater with anomalously high carbonate saturation necessary to preserve delicate microbial textures. This work has implications for the understanding of three-dimensional biofilm architecture that goes beyond the current micro-scale observations available from living biofilm experiments and suggests that biofilm channel networks have an extensive fossil record.

Fossil Geyserite and Testate Amoebae in Geothermal Spring Vent Pools: Paleoecology and Variable Preservation Quality in Jurassic Sinter of Patagonia (Deseado Massif, Argentina).

Geyserite is a type of terrestrial siliceous hot spring deposit (sinter) formed subaerially in proximal vent areas, with near-neutral pH, alkali chloride discharge fluids characterized by initial high temperatures (~73°C to up to 100°C) that fluctuate rapidly in relation to dynamic hydrology, seasonality, wind, and other environmental parameters. We analyzed sinters at the Claudia paleogeothermal field from the Late Jurassic (~150 Ma) Deseado Massif geological province, Argentinean Patagonia. The geyserite samples-with spicular to columnar to nodular morphologies-contain abundant microfossils in monotypic assemblages that occur in three diagenetic states of preservation. The best-preserved microfossils consist of vesicle-like structures with radial heteropolar symmetry (~35 μm average diameter), circular apertures, smooth walls lacking ornamentation, and disk- or beret-like shapes. Comparisons with extant, morphologically similar organisms suggest an affinity with the testate amoebae of the Arcella hemisphaerica-Arcella rotundata complex and Centropyxis aculeata strain discoides. These species occur in active geothermal pools between 22°C and 45°C, inconsistent with the temperature of formation of modern geyserites. We propose that the testate amoebae may have colonized the geyserite during cooler phases in between spring-vent eruptive cycles to prey on biofilms. Silica precipitation through intermittent bathing and splashing of fluctuating thermal fluid discharge could have led to their entrapment and fossilization. Petrographic analysis supports cyclicity in paleovent water eruptions and later diagenesis that transformed the opal into quartz. Spatially patchy degradation and modification of the silicified microorganisms resulted in variable preservation quality of the microfossils. This contribution illustrates the importance of microscale analysis to locate early silicification and identify high-quality preservation of fossil remains in siliceous hot spring deposits, which are important in early life studies on Earth and potentially Mars.

The Palaeobiology of Two Crown Group Cnidarians: Haootia quadriformis and Mamsetia manunis gen. et sp. nov. from the Ediacaran of Newfoundland, Canada.

The Ediacaran of eastern Newfoundland preserves the world's oldest known eumetazoan body fossils, as well as the earliest known record of fossilized muscular tissue. Re-examination of the holotype of the eight-armed Haootia quadriformis in terms of its morphology, the arrangement of its muscle filament bundles, and hitherto undescribed aspects of its anatomy support its interpretation as a crown staurozoan. We also document several new fossils preserving muscle tissue with a different muscular architecture to Haootia, but with only four arms. This new material allows us to describe a new crown group staurozoan, Mamsetia manunis gen. et sp. nov. This work confirms the presence of crown group medusozoan cnidarians of the Staurozoa in the Ediacaran of Newfoundland circa 565 Ma.

Ichnological records associated with dermestid beetles in dinosaur bones from Lala's Place (Maastrichtian), Ramos Arizpe, Coahuila, Mexico, and their taphonomic implications

We analyzed the ichnological record of hadrosaur remains from the dinosaur quarry CLP-3, Lala's Place, Ramos Arizpe, Coahuila, where taphonomic research is ongoing. These fossils have been determined to stratigraphically belong to the Cerro del Pueblo Formation, deposited in a deltaic floodplain environment. The Lala's Place quarries have been determined to belong to the early Maastrichtian (69 ± 5 Ma) through U/Pb detrital zircon dating. Thirteen trace fossil morphotypes were identified in six bone elements, interpreted to belong to a single individual. These traces were identified to belong to the ichnospecies Cuniculichnus seilacheri, cf. Cubiculum cooperi, Cubiculum atsintli. A new ichnospecies, Cubiculum subcorticalis n. isp., characterized by a composite feeding-pupation trace with subcortical chambers, is also described. Based on these findings, temporal range of the previously described ichnospecies is expanded to the Maastrichtian stage in the Cerro del Pueblo Formation. Previous work has reported these ichnospecies and associated them with dermestid beetles; this work also associates these traces with dermestids through morphological analyses and using for the first time the novel Usefulness in Identification and Differentiation (UID) index, recently proposed for this taxon. These traces indicate that the carcass was exposed to a subaerial environment for at least 20–30 days, reaching a dry stage in which dermestid adults fed, reproduced, and oviposited. Larvae produced these traces by excavating chambers to avoid cannibalism by other larvae.