Hydrodynamic insights into the paleobiology of the Ediacaran rangeomorph Fractofusus misrai.

The Ediacaran of Newfoundland preserves some of the oldest complex macroscopic communities, several of which are dominated by the fractal-like rangeomorph genus Fractofusus. Here we use computational fluid dynamics and a detailed reconstruction of Fractofusus misrai to document for the first time hydrodynamic phenomena associated with this sediment-reclining organism and its rangeomorph elements that are relevant to interpreting feeding strategies, explain the recently documented rheotropic growth oblique to currents, and provide insights into their impact on the Ediacaran seafloor. Obliquely oriented Fractofusus are common, likely representing a compromise between maximized aspect ratio and minimization of drag. Flow patterns on the upper surface of Fractofusus are consistent with the collection of dissolved and finely particulate nutrients, as well as gas exchange. Fractofusus produce a wake downstream, demonstrating that reclining rangeomorphs had potential to modify sedimentation patterns on the ancient seafloor by potentially allowing deposition of fine-grained sediment.

Charcoal evidence traces diverse fungal metabolic strategies to the Late Paleozoic.

Wood decomposition through fungal activity is essential to the natural carbon cycle. There are three primary patterns of wood decay: white rot, brown rot, and soft rot. However, geological records of wood decay mainly originate from fossil woods, which exclusively describe white rot before the Cenozoic. Fossilized charcoal is another excellent medium for preserving pre-charring decay structures. In this study, we collected numerous charcoals from the upper Permian and observed multiple microstructures indicative of wood decay. The distinctive characteristics closely resemble the symptoms of contemporary wood-rotting types, including the removal of the middle lamella and channel-like lysis seen in white rot, shot-like holes and wavy cell walls in brown rot, and cavities within the secondary walls in soft rot. This study documents the early occurrences of multiple wood-rotting types during the Late Paleozoic and provides insights into the range of fungal metabolic strategies employed during this period.

On the scientific credibility of paleoanthropology.

Smith and Smith and Wood proposed that the human fossil record offers special challenges for causal hypotheses because "unique" adaptations resist the comparative method. We challenge their notions of "uniqueness" and offer a refutation of the idea that there is something epistemologically special about human prehistoric data. Although paleontological data may be sparse, there is nothing inherent about this information that prevents its use in the inductive or deductive process, nor in the generation and testing of scientific hypotheses. The imprecision of the fossil record is well-understood, and such imprecision is often factored into hypotheses and methods. While we acknowledge some oversteps within the discipline, we also note that the history of paleoanthropology is clearly one of progress, with ideas tested and resolution added as data (fossils) are uncovered and new technologies applied, much like in sciences as diverse as astronomy, molecular genetics, and geology.

An extinct north American porcupine with a South American tail.

New World porcupines (Erethizontinae) originated in South America and dispersed into North America as part of the Great American Biotic Interchange (GABI) 3-4 million years ago.1 Extant prehensile-tailed porcupines (Coendou) today live in tropical forests of Central and South America.2,3 In contrast, North American porcupines (Erethizon dorsatum) are thought to be ecologically adapted to higher-latitude temperate forests, with a larger body, shorter tail, and diet that includes bark.4,5,6,7 Limited fossils8,9,10,11,12,13 have hindered our understanding of the timing of this ecological differentiation relative to intercontinental dispersal during the GABI and expansion into temperate habitats.14,15,16,17,18 Here, we describe functionally important features of the skeleton of the extinct Erethizon poyeri, the oldest nearly complete porcupine skeleton documented from North America, found in the early Pleistocene of Florida. It differs from extant E. dorsatum in having a long, prehensile tail, grasping foot, and lacking dental specializations for bark gnawing, similar to tropical Coendou. Results from phylogenetic analysis suggest that the more arboreal characteristics found in E. poyeri are ancestral for erethizontines. Only after it expanded into temperate, Nearctic habitats did Erethizon acquire the characteristic features that it is known for today. When combined with molecular estimates of divergence times, results suggest that Erethizon was ecologically similar to a larger species of Coendou when it crossed the Isthmus of Panama by the early Pleistocene. It is likely that the range of this more tropically adapted form was limited to a continuous forested biome that extended from South America through the Gulf Coast.

The "elongate chelicera problem": A virtual approach in an extinct pterygotid sea scorpion from a 3D kinematic point of view.

Chelicerae, distinctive feeding appendages in chelicerates, such as spiders, scorpions, or horseshoe crabs, can be classified based on their orientation relative to the body axis simplified as either orthognathous (parallel) or labidognathous (inclined), exhibiting considerable diversity across various taxa. Among extinct chelicerates, sea scorpions belonging to the Pterygotidae represent the only chelicerates possessing markedly elongated chelicerae relative to body length. Despite various hypotheses regarding the potential ecological functions and feeding movements of these structures, no comprehensive 3D kinematic investigation has been conducted yet to test these ideas. In this study, we generated a comprehensive 3D model of the pterygotid Acutiramus, making the elongated right chelicera movable by equipping it with virtual joint axes for conducting Range of Motion analyses. Due to the absence in the fossil record of a clear indication of the chelicerae orientation and their potential lateral or ventral movements (vertical or horizontal insertion of joint axis 1), we explored the Range of Motion analyses under four distinct kinematic settings with two orientation modes (euthygnathous, klinogathous) analogous to the terminology of the terrestrial relatives. The most plausible kinematic setting involved euthygnathous chelicerae being folded ventrally over a horizontal joint axis. This configuration positioned the chelicera closest to the oral opening. Concerning the maximum excursion angle, our analysis revealed that the chela could open up to 70°, while it could be retracted against the basal element to a maximum of 145°. The maximum excursion in the proximal joint varied between 55° and 120° based on the insertion and orientation. Our findings underscore the utility of applying 3D kinematics to fossilized arthropods for addressing inquiries on functional ecology such as prey capture and handling, enabling insights into their possible behavioral patterns. Pterygotidae likely captured and processed their prey using the chelicerae, subsequently transporting it to the oral opening with the assistance of other prosomal appendages.

A modern definition of Fossil-Lagerstätten.

Fossil-Lagerstätten are amongst the most important windows onto the paleobiology of ancient ecosystems. Inconsistencies surrounding what constitutes a Lagerstätte limits our ability to compare sites and thus their scientific potential. Here, we provide a modern and utilitarian classification scheme for Konservat-Lagerstätten, allowing for more consistent and improved scientific discourse.

Extinct and extant termites reveal the fidelity of behavior fossilization in amber.

Fossils encompassing multiple individuals provide rare direct evidence of behavioral interactions among extinct organisms. However, the fossilization process can alter the spatial relationship between individuals and hinder behavioral reconstruction. Here, we report a Baltic amber inclusion preserving a female-male pair of the extinct termite species Electrotermes affinis. The head-to-abdomen contact in the fossilized pair resembles the tandem courtship behavior of extant termites, although their parallel body alignment differs from the linear alignment typical of tandem runs. To solve this inconsistency, we simulated the first stage of amber formation, the immobilization of captured organisms, by exposing living termite tandems to sticky surfaces. We found that the posture of the fossilized pair matches trapped tandems and differs from untrapped tandems. Thus, the fossilized pair likely is a tandem running pair, representing the direct evidence of the mating behavior of extinct termites. Furthermore, by comparing the postures of partners on a sticky surface and in the amber inclusion, we estimated that the male likely performed the leader role in the fossilized tandem. Our results demonstrate that past behavioral interactions can be reconstructed despite the spatial distortion of body poses during fossilization. Our taphonomic approach demonstrates how certain behaviors can be inferred from fossil occurrences.

A juvenile bird with possible crown-group affinities from a dinosaur-rich Cretaceous ecosystem in North America.

BACKGROUND: Living birds comprise the most speciose and anatomically diverse clade of flying vertebrates, but their poor early fossil record and the lack of resolution around the relationships of the major clades have greatly obscured extant avian origins. RESULTS: Here, I describe a Late Cretaceous bird from North America based on a fragmentary skeleton that includes cranial material and portions of the forelimb, hindlimb, and foot and is identified as a juvenile based on bone surface texture. Several features unite this specimen with crown Aves, but its juvenile status precludes the recognition of a distinct taxon. The North American provenance of the specimen supports a cosmopolitan distribution of early crown birds, clashes with the hypothesized southern hemisphere origins of living birds, and demonstrates that crown birds and their closest relatives coexisted with non-avian dinosaurs that independently converged on avian skeletal anatomy, such as the alvarezsaurids and dromaeosaurids. CONCLUSIONS: By revealing the ecological and biogeographic context of Cretaceous birds within or near the crown clade, the Lance Formation specimen provides new insights into the contingent nature of crown avian survival through the Cretaceous-Paleogene mass extinction and the subsequent origins of living bird diversity.

Automated graptolite identification at high taxonomic resolution using residual networks.

Graptolites, fossils significant for evolutionary studies and shale gas exploration, are traditionally identified visually by taxonomists due to their intricate morphologies and preservation challenges. Artificial intelligence (AI) holds great promise for transforming such meticulous tasks. In this paper, we demonstrate that graptolites can be identified with taxonomist accuracy using a deep learning model. We construct the most sophisticated and largest professional single organisms image dataset to date, which is composed of >34,000 images of 113 graptolite species annotated at pixel-level resolution to train the model, develop, and evaluate deep learning networks to classify graptolites. The model's performance surpassed taxonomists in accuracy, time, and generalization, achieving 86% and 81% accuracy in identifying graptolite genus and species, respectively. This AI-based method, capable of recognizing minute morphological details better than taxonomists, can be integrated into web and mobile apps, extending graptolite identification beyond research institutes and enhancing shale gas exploration efficiency.

Distinctive microfossil supports early Paleoproterozoic rise in complex cellular organisation.

The great oxidation event (GOE), ~2.4 billion years ago, caused fundamental changes to the chemistry of Earth's surface environments. However, the effect of these changes on the biosphere is unknown, due to a worldwide lack of well-preserved fossils from this time. Here, we investigate exceptionally preserved, large spherical aggregate (SA) microfossils permineralised in chert from the c. 2.4 Ga Turee Creek Group in Western Australia. Field and petrographic observations, Raman spectroscopic mapping, and in situ carbon isotopic analyses uncover insights into the morphology, habitat, reproduction and metabolism of this unusual form, whose distinctive, SA morphology has no known counterpart in the fossil record. Comparative analysis with microfossils from before the GOE reveals the large SA microfossils represent a step-up in cellular organisation. Morphological comparison to extant micro-organisms indicates the SAs have more in common with coenobial algae than coccoidal bacteria, emphasising the complexity of this microfossil form. The remarkable preservation here provides a unique window into the biosphere, revealing an increase in the complexity of life coinciding with the GOE.

Soft robotics informs how an early echinoderm moved.

The transition from sessile suspension to active mobile detritus feeding in early echinoderms (c.a. 500 Mya) required sophisticated locomotion strategies. However, understanding locomotion adopted by extinct animals in the absence of trace fossils and modern analogues is extremely challenging. Here, we develop a biomimetic soft robot testbed with accompanying computational simulation to understand fundamental principles of locomotion in one of the most enigmatic mobile groups of early stalked echinoderms-pleurocystitids. We show that these Paleozoic echinoderms were likely able to move over the sea bottom by means of a muscular stem that pushed the animal forward (anteriorly). We also demonstrate that wide, sweeping gaits could have been the most effective for these echinoderms and that increasing stem length might have significantly increased velocity with minimal additional energy cost. The overall approach followed here, which we call "Paleobionics," is a nascent but rapidly developing research agenda in which robots are designed based on extinct organisms to generate insights in engineering and evolution.

A 50-million-year-old, three-dimensionally preserved bat skull supports an early origin for modern echolocation.

Bats are among the most recognizable, numerous, and widespread of all mammals. But much of their fossil record is missing, and bat origins remain poorly understood, as do the relationships of early to modern bats. Here, we describe a new early Eocene bat that helps bridge the gap between archaic stem bats and the hyperdiverse modern bat radiation of more than 1,460 living species. Recovered from ∼50 million-year-old cave sediments in the Quercy Phosphorites of southwestern France, Vielasia sigei's remains include a near-complete, three-dimensionally preserved skull-the oldest uncrushed bat cranium yet found. Phylogenetic analyses of a 2,665 craniodental character matrix, with and without 36.8 kb of DNA sequence data, place Vielasia outside modern bats, with total evidence tip-dating placing it sister to the crown clade. Vielasia retains the archaic dentition and skeletal features typical of early Eocene bats, but its inner ear shows specializations found in modern echolocating bats. These features, which include a petrosal only loosely attached to the basicranium, an expanded cochlea representing ∼25% basicranial width, and a long basilar membrane, collectively suggest that the kind of laryngeal echolocation used by most modern bats predates the crown radiation. At least 23 individuals of V. sigei are preserved together in a limestone cave deposit, indicating that cave roosting behavior had evolved in bats by the end of the early Eocene; this period saw the beginning of significant global climate cooling that may have been an evolutionary driver for bats to first congregate in caves.

Fungal spores in Caribbean mangrove sediments, dataset from southeastern Mexico.

Most paleoecological investigations use different biotic or abiotic proxies for climate and environmental reconstructions. Although fossil pollen is one of the most used biological proxies, Non-Pollen Palynomorphs (NPPs), especially fungal spores and tissues, have an underestimated potential to infer local and regional climate dynamics. This dataset describes the most common Non-pollen palynomorphs of fungal origin from mangrove sediments in the Caribbean Sea, southeastern Mexico. A detailed descriptive Atlas is presented, with light micrographs taken from routine pollen slides in paleoecological reconstructions. Microphotographs were included to facilitate their identification. A total of 59 spores, 4 tissues, 2 hyphae, and 11 unidentified fungal palynomorphs are described.

Microbially mediated fossil concretions and their characterization by the latest methodologies: a review.

The study of well-preserved organic matter (OM) within mineral concretions has provided key insights into depositional and environmental conditions in deep time. Concretions of varied compositions, including carbonate, phosphate, and iron-based minerals, have been found to host exceptionally preserved fossils. Organic geochemical characterization of concretion-encapsulated OM promises valuable new information of fossil preservation, paleoenvironments, and even direct taxonomic information to further illuminate the evolutionary dynamics of our planet and its biota. Full exploitation of this largely untapped geochemical archive, however, requires a sophisticated understanding of the prevalence, formation controls and OM sequestration properties of mineral concretions. Past research has led to the proposal of different models of concretion formation and OM preservation. Nevertheless, the formation mechanisms and controls on OM preservation in concretions remain poorly understood. Here we provide a detailed review of the main types of concretions and formation pathways with a focus on the role of microbes and their metabolic activities. In addition, we provide a comprehensive account of organic geochemical, and complimentary inorganic geochemical, morphological, microbial and paleontological, analytical methods, including recent advancements, relevant to the characterization of concretions and sequestered OM. The application and outcome of several early organic geochemical studies of concretion-impregnated OM are included to demonstrate how this underexploited geo-biological record can provide new insights into the Earth's evolutionary record. This paper also attempts to shed light on the current status of this research and major challenges that lie ahead in the further application of geo-paleo-microbial and organic geochemical research of concretions and their host fossils. Recent efforts to bridge the knowledge and communication gaps in this multidisciplinary research area are also discussed, with particular emphasis on research with significance for interpreting the molecular record in extraordinarily preserved fossils.

The role of clay minerals in the preservation of Precambrian organic-walled microfossils.

Precambrian organic-walled microfossils (OWMs) are primarily preserved in mudstones and shales that are low in total organic carbon (TOC). Recent work suggests that high TOC may hinder OWM preservation, perhaps because it interferes with chemical interactions involving certain clay minerals that inhibit the decay of microorganisms. To test if clay mineralogy controls OWM preservation, and if TOC moderates the effect of clay minerals, we compared OWM preservational quality (measured by pitting on fossil surfaces and the deterioration of wall margins) to TOC, total clay, and specific clay mineral concentrations in 78 shale samples from 11 lithologic units ranging in age from ca. 1650 to 650 million years ago. We found that the probability of finding well-preserved microfossils positively correlates with total clay concentrations and confirmed that it negatively correlates with TOC concentrations. However, we found no evidence that TOC influences the effect of clay mineral concentrations on OWM preservation, supporting an independent role of both factors on preservation. Within the total clay fraction, well-preserved microfossils are more likely to occur in shales with high illite concentrations and low berthierine/chamosite concentrations; however, the magnitude of their effect on preservation is small. Therefore, there is little evidence that bulk clay chemistry is important in OWM preservation. Instead, we propose that OWM preservation is largely regulated by physical properties that isolate organic remains from microbial degradation such as food scarcity (low TOC) and low sediment permeability (high total clay content): low TOC increases the diffusive distances between potential carbon sources and heterotrophic microbes (or their degradative enzymes), while high clay concentrations reduce sediment pore space, thereby limiting the diffusion of oxidants and degradative enzymes to the sites of decay.

Insular giant leporid matured later than predicted by scaling.

The island syndrome describes morphological, behavioral, and life history traits that evolve in parallel in endemic insular organisms. A basic axiom of the island syndrome is that insular endemics slow down their pace of life. Although this is already confirmed for insular dwarfs, a slow life history in giants may not be adaptive, but merely a consequence of increasing body size. We tested this question in the fossil insular giant leporid Nuralagus rex. Using bone histology, we constructed both a continental extant taxon model derived from experimentally fluorochrome-labeled Lepus europaeus to calibrate life history events, and a growth model for the insular taxon. N. rex grew extremely slowly and delayed maturity well beyond predictions from continental phylogenetically corrected scaling models. Our results support the life history axiom of the island syndrome as generality for insular mammals, regardless of whether they have evolved into dwarfs or giants.

Miocene phytolith and diatom dataset from 10.3Myo diatomite formation, Fernley, Nevada, USA.

Phytoliths are opal silica particles formed within plant tissues. Diatoms are aquatic, single-celled photosynthetic algae with silica skeletons. Phytolith and diatom morphotypes vary depending on local environmental and climatic conditions and because their silicate structures preserve well, the study of phytolith and diatom morphotypes can be used to better understand paleoclimatic and paleoenvironmental dynamics and changes. This article presents original data from an 820cm-deep stratigraphy excavated at the Hazen diatomite deposits, a high-elevation desert paleolake in the Fernley District, Northern Nevada, USA. The site has been studied for an assemblage of fossilized threespine stickleback, Gasterosteus doryssus, that reveal adaptive evolution. For this study, a total of 157 samples were extracted at 20 cm intervals covering approximately 24,500 years. After extraction, the samples were mounted on slides and viewed under 400-1000x light microscopy, enabling classification of 14 phytolith and 45 diatom morphotypes. Our data support paleoenvironmental reconstructions of the Hazen Miocene paleolake.

Skeletal anatomy of the early Permian parareptile Delorhynchus with new information provided by neutron tomography.

Detailed description of the holotype skeleton of Delorhynchus cifellii, made possible through the use of neutron tomography, has yielded important new information about the cranial and postcranial anatomy of this early Permian acleistorhinid parareptile. Hitherto unknown features of the skull include a sphenethmoid, paired epipterygoids and a complete neurocranium. In addition, the stapes has been exposed in three dimensions for the first time in an early parareptile. Postcranial material found in articulation with the skull in this holotype allows for the first detailed description of vertebrae, ribs, shoulder girdle and humerus of an acleistorhinid parareptile, allowing for a reevaluation of the phylogenetic relationships of this taxon with other acleistorhinids, and more broadly among parareptiles. Results show that Delorhynchus is recovered as the sister taxon of Colobomycter, and 'acleistorhinids' now include Lanthanosuchus.

Understanding locomotion in trilobites by means of three-dimensional models.

Trilobites were one of the first animals on Earth to leave their imprints on the seafloor. Such imprints represent behavioral traces related to feeding or protection, in both cases implying different types of locomotion. Modeling how trilobites moved is essential to understand their evolutionary history and ecological impact on marine substrates. Herein, locomotion in trilobites is approached by means of three-dimensional models, which yielded two main gait types. These two gaits reflect basic behaviors: burrowing and walking. This model reveals that trilobites could change their gait and consequently increase rapidly their speed varying the amplitude of the metachronal wave, a change independent from their biological structure. Fast increases in speed enhanced the protection of trilobites against predators and sudden environmental crises. The trilobite body pattern constrained their gaits, controlled by the distance between the pair of legs and between legs in a same segment.

Adaptive evolution of the enigmatic Takakia now facing climate change in Tibet.

The most extreme environments are the most vulnerable to transformation under a rapidly changing climate. These ecosystems harbor some of the most specialized species, which will likely suffer the highest extinction rates. We document the steepest temperature increase (2010-2021) on record at altitudes of above 4,000 m, triggering a decline of the relictual and highly adapted moss Takakia lepidozioides. Its de-novo-sequenced genome with 27,467 protein-coding genes includes distinct adaptations to abiotic stresses and comprises the largest number of fast-evolving genes under positive selection. The uplift of the study site in the last 65 million years has resulted in life-threatening UV-B radiation and drastically reduced temperatures, and we detected several of the molecular adaptations of Takakia to these environmental changes. Surprisingly, specific morphological features likely occurred earlier than 165 mya in much warmer environments. Following nearly 400 million years of evolution and resilience, this species is now facing extinction.