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bioRxiv2019

Messinian vegetation and climate of the intermontane Florina-Ptolemais-Servia Basin, NW Greece inferred from palaeobotanical data: How well do plant fossils reflect past environments?

The late Miocene is marked by pronounced environmental changes and the appearance of strong temperature and precipitation seasonality. Although environmental heterogeneity is to be expected during this time, it is challenging to reconstruct palaeoenvironments using plant fossils. We investigated leaves and dispersed spores/pollen from 6.4-6 Ma strata in the intermontane Florina-Ptolemais-Servia Basin (FPS) of northwestern Greece. To assess how well plant fossils reflect the actual vegetation of the FPS, we assigned fossil-taxa to biomes providing a measure for environmental heterogeneity. Additionally, the palynological assemblage was compared to pollen spectra from modern lake sediments to assess biases in spore/pollen representation in the pollen record. We found a close match of the Vegora assemblage with modern Fagus-Abies forests of Turkey. Using taxonomic affinities of leaf fossils, we further established close similarities of the Vegora assemblage with modern laurophyllous oak forests of Afghanistan. Finally, using information from sedimentary environment and taphonomy, we distinguished local and distantly growing vegetation types. We then subjected the plant assemblage of Vegora to different methods of climate reconstruction and discussed their potentials and limitations. Leaf and spore/pollen records allow accurate reconstructions of palaeoenvironments in the FPS, whereas extra-regional vegetation from coastal lowlands is likely not captured.

paleontology↗
bioRxiv2019

Transitional evolutionary forms and stratigraphic trends in chasmosaurine ceratopsid dinosaurs : evidence from the Campanian of New Mexico

ABSTRACTThree new chasmosaurines from the Kirtland Formation (∼75.0 - 73.4 Ma), New Mexico, form morphological and stratigraphic intermediates between Pentaceratops (∼74.7 - 75Ma, Fruitland Formation, New Mexico) and Anchiceratops (∼72 - 71Ma, Horseshoe Canyon Formation, Alberta). The new specimens exhibit gradual enclosure of the parietal embayment that characterizes Pentaceratops, providing support for the phylogenetic hypothesis that Pentaceratops and Anchiceratops are closely related. This stepwise change of morphologic characters observed in chasmosaurine taxa that do not overlap stratigraphically is supportive of evolution by anagenesis. Recently published hypotheses that place Pentaceratops and Anchiceratops into separate clades are not supported. This phylogenetic relationship demonstrates unrestricted movement of large-bodied taxa between hitherto purported northern and southern provinces in the Late Campanian, weakening support for the hypothesis of extreme faunal provincialism in the Late Cretaceous Western Interior.View Full Text

paleontology↗
bioRxiv2019

Effectiveness of micromorphy against drilling predation: Insights from early Miocene faunal assemblage of Quilon limestone, India

The nature of drilling predation, although well documented for molluscan fossils, is understudied for micromolluscs (<5mm). Studying predation in micromolluscs is especially critical in evaluating the adaptive significance of micromorphy against predation and assessing the importance of predator-prey size relationship (PPSR). This study documents drilling predation event in microbivalves from early Miocene (Burdigalian) fossil assemblage of Quilon limestone from Kerala, India. Our sample of ~2000 valves represent nine families with an average drilling frequency (DF) of 0.06 and an incomplete drilling frequency (IDF) of 0.26. The characteristic drillhole morphology and occurrence of five genera of modern drilling gastropods (Naticid: Natica, Tanea and Polinices; Muricid: Triplex and Dermomurex) from the same locality reveals the predator identity. Predation in the studied assemblage is found to be highly selective in terms of prey taxa, size, mobility and site selection. Six out of nine families show evidence of predation indicating taxon selectivity. Poor correlation between DF and abundance further supports this view. Failed attacks are strongly correlated with morphological features such as surface ornamentation (Lucinidae), presence of conchiolin layers (Corbulidae). Drilling occurs primarily on medium size class and prey outside this size range show lower rate of attack. This indicates the existence of an “inverse size refugia” for extremely small prey along with the classical size refugia existing for large prey. Mobility is found to be a deterrent to drilling predation and it also increases failure. Microbenthos of Quilon limestone shows a lower predation intensity in comparison to the Miocene macrobenthos worldwide including coeval formation of the Kutch Basin. The interaction in microbenthos is more strongly size-dependent in contrast to the Kutch fauna. Reduced predation intensity in microfauna and existence of “inverse size refugia” support the claim of micromorphy acting as a defense mechanism and highlights the role of size-dependent predation in marine benthos.

paleontology↗
bioRxiv2019

The influence of environmental setting on the community ecology of Ediacaran organisms

The broad-scale environment plays a substantial role in shaping modern marine ecosystems, but the degree to which palaeocommunities were influenced by their environment is unclear. To investigate how broad-scale environment influenced the community ecology of early animal ecosystems we employed spatial point process analyses to examine the community structure of seven bedding-plane assemblages of late Ediacaran age (558–550 Ma), drawn from a range of environmental settings and global localities. The studied palaeocommunities exhibit marked differences in the response of their component taxa to sub-metre-scale habitat heterogeneities on the seafloor. Shallow-marine palaeocommunities were heavily influenced by local habitat heterogeneities, in contrast to their deep-water counterparts. Lower species richness in deep-water Ediacaran assemblages compared to shallow-water counterparts across the studied time-interval could have been driven by this environmental patchiness, because habitat heterogeneities correspond to higher diversity in modern marine environments. The presence of grazers and detritivores within shallow-water communities may have promoted local patchiness, potentially initiating a chain of increasing heterogeneity of benthic communities from shallow to deep-marine depositional environments. Our results provide quantitative support for the “Savannah” hypothesis for early animal diversification – whereby Ediacaran diversification was driven by patchiness in the local benthic environment.Author Contributions E. Mitchell conceived this paper and wrote the first draft. N. Bobkov, A. Kolesnikov, N. Sozonov and D. Grazhdankin collected the data for DS surface. N. Bobkov and N. Sozonov performed the analyses on DS surface. N. Bykova, S. Xiao, and D. Grazhdankin collected the data for WS, KH1 and KH2 surfaces and E. Mitchell performed the analyses. A. Dhungana and A. Liu collected the data for FUN4 and FUN5 surfaces and A. Dhungana performed the analyses. T. Mustill and D. Grazhdankin collected the data for KS and T. Mustill and E. Mitchell performed the analyses. I. Hogarth developed the software for preliminary KS surface analyses. E. Mitchell, N. Bobkov, N. Bykova, A. Dhungana, A. Kolesnikov, A. Liu, S. Xiao and D. Grazhdankin discussed the results and prepared the manuscript.View Full Text

paleontology↗
bioRxiv2019

Low-Latitude Origins of the Four Phanerozoic Evolutionary Faunas

The hypothesis of the Great Evolutionary Faunas is a foundational concept of macroevolutionary research postulating that three global mega-assemblages have dominated Phanerozoic oceans following abrupt biotic transitions. Empirical estimates of this large-scale pattern depend on several methodological decisions and are based on approaches unable to capture multiscale dynamics of the underlying Earth-Life System. Combining a multilayer network representation of fossil data with a multilevel clustering that eliminates the subjectivity inherent to distance-based approaches, we demonstrate that Phanerozoic oceans sequentially harbored four global benthic mega-assemblages. Shifts in dominance patterns among these global marine mega-assemblages are abrupt (end-Cambrian 494 Ma; end-Permian 252 Ma) or protracted (mid-Cretaceous 129 Ma), and represent the three major biotic transitions in Earths history. This finding suggests that the mid-Cretaceous radiation of the so-called Modern evolutionary Fauna, concurrent with gradual ecological changes associated with the Mesozoic Marine Revolution, triggered a biotic transition comparably to the transition following the largest extinction event in the Phanerozoic. Overall, our study supports the notion that both long-term ecological changes and major geological events have played crucial roles in shaping mega-assemblages that dominated Phanerozoic oceans.

paleontology↗
bioRxiv2025

Examples of adaptive peak tracking as found in the fossil record

Species that have persisted over millions of years have done so because they have been able to track peaks in an adaptive landscape well enough to survive and reproduce. Such optima are defined by the mean phenotypic values that maximize mean fitness, and they are predominantly functions of the environment, for example the sea temperature. The mean phenotypic values over time will thus predominantly be determined by the environment over time, and the trait history may be found in the fossil record. Here I use fossil data from three cases found in the literature, and I show that adaptive peak tracking models give better results than alternative weighted least squares and directional random walk models. The model performances are compared by use of weighted mean squared errors and Akaike information criterion results.

paleontology↗
bioRxiv2025

Reinterpretation of Bakiribu waridza from the Romualdo Formation (Lower Cretaceous) of Brazil: a fish not a pterosaur

Fragmentary remains of fossil vertebrates from the Romualdo Formation (Lower Cretaceous) of Brazil, preserved in association with two fish were interpreted as two individuals of a new genus and species of ctenochasmatine pterosaur, Bakiribu waridza Pegas et al., 2025. Comparison with a range of fossils from the same geological unit show that the remains represent the gill arch apparatus of a large actinopterygian fish. This reinterpretation, which mirrors a comparable event in the mid twentieth century when the remains of a supposed ctenochasmatine pterosaur, Belonochasma aenigmaticum, were reidentified as part of the gill apparatus of a fish, does not affect our current understanding of the evolutionary history of pterosaurs.

paleontology↗
bioRxiv2025

The taxonomics of the diverse, lithe basal eutyrannosaur genera and species of late Maastrichtian western North America

In 1946 Gilmore observed that the Hell Creek Formation portion of the late Maastrichtian TT-zone contained more tyrannosaur taxa than just titanic Tyrannosaurus rex, based on a small, ontogenetically mature skull with a higher tooth count than the tyrant lizard. Over four decades later the skull was assigned to its own genus, Nanotyrannus lancensis. Also tagged shortly after was the genus Stygivenator molnari. At the turn of the century it was contended that all TT-zone tyrannosaurs are adult or juvenile T. rex, a view that became accepted by many. Because of the unusual morphological alterations that this hypothesis requires, it was consequently proposed that during ontogeny T. rex experienced a peculiar fish like metamorphosis. Detailing normal amniote growth more broadly than prior work on the subject, this analysis rejects radical ontogenetic speculations, in favor of Tyrannosaurus having shared much the same average amniote/diapsid conventional growth observed in its fellow tyrannosaurids and especially tyrannosaurins. Actual juvenile Tyrannosaurus specimens show the same tooth count and other osteological features observed in the adults, negating the need for the metamorphosis not observed in any amniotes. Most lesser sized TT-zone tyrannosaurs possess a number of features that indicate they are not only not Tyrannosaurus, but represent an array of basal eutyrannosaur taxa that are neither Nanotyrannus nor Stygivenator, with high tooth counts, and at least in some examples elongated hands, prominent dentary grooves and other features. Two new taxa are correspondingly named, Gilmorelarsontyrannus lethaeus and Elegansvenator zannoae. These are postulated to represent at least in part the migration of basal eutyrannosaurs from former Appalachia into the Laramidia region via the new Laralachia land bridge. The total number of tyrannosaur taxa now known to have inhabited the TT-zone for over 1 MA is seven species in five genera from multiple subfamilies, with a smaller portion of this collection extant at any given stratigraphic level.

paleontology↗
bioRxiv2025

Garamaudo bauciensis, a new freshwater Mosasauridae (Reptilia, Squamata) from the Santonian (Late Cretaceous) of Provence, southeastern France

Mosasauroids are primarily known as aquatic squamates that diversified in the marine realm during the Late Cretaceous. While most species had paddles, an elongated skull and body, and a laterally compressed tail, and lived in the open sea, some early species, with limbs similar to those of terrestrial animals and a varanoidlike body, lived in marine coastal shallow waters. Recently, mosasauroid remains have been discovered in freshwater environments in several continental deposits of the Santonian-Campanian of Europe. This study describes new cranial and postcranial mosasauroid remains from Santonian continental deposits in Provence, southeastern France, and attributes them to a new tethysaurine: Garamaudo bauciensis gen. et sp. nov. This mosasauroid, approximately 2.5 m long, with limbs looking adapted for a terrestrial locomotion and a sacrum, and with osteosclerosis in its vertebrae and humerus (at least), probably hovered at shallow depth in freshwater ecosystems. This new discovery reveals that it is only within the Tethysaurinae that multiple freshwater forms evolved, pointing to possible niche partitioning, associated with the retention of the plesiopedal / plesiopelvic condition, in parallel with the invasion of open waters by most other hydropedal and hydropelvic mosasauroids. These considerations suggest a richer evolutionary history of mosasauroids than is currently assumed.

paleontology↗
bioRxiv2025

Theoretical Morphology of Avian Wing Planform Reveals Variable Optimisation to Flight Style

Bird wings exhibit a broad degree of functional and shape variation, though the exact nature of the form-function relationship is uncertain. Recent analysis suggests that functional variability is explained by linear non-shape-based traits and that shape variation is largely explained by phylogeny. We assay the relationship between wing planform shape and functional performance using a theoretical morphospace approach that eschews assumptions of the functional optimality of empirical morphologies. Empirical properties are considered post hoc relative to their positions in the functional performance landscapes. We produce a theoretical morphospace of wing planform shapes and compare the functional performance and optimality of theoretical shapes with 1139 extant taxa. These tests cover flight metrics and combinations linked with 7 flight niches. Metrics pertaining to agile flight strongly constrain shape, with hovering, diving and hawking birds developing optimal planforms. Marine soarers are suboptimal for metrics linked with efficient and manoeuvrable flight. Many taxa, principally passerines, remain suboptimal for all studied metrics and combinations. This suggests flight performance constrains planforms unevenly across birds. Phylomorphospace analysis suggests planform shape is only weakly influenced by phylogeny and functional optimality correlates closely with flight styles. This suggests wing shape remains a determining factor in how birds fly.

paleontology↗
bioRxiv2025

Homology of the dark cells of Paleozoic liverworts with the specialized oil body cells of modern liverworts (Marchantiophyta)

O_LIOil bodies are a synapomorphy of liverworts (Marchantiophyta), a major group of land plants with a sparse fossil record. Paleozoic liverworts sometimes possess dark cells that appear similar in distribution to liverwort oil body cells. The Middle Devonian Metzgeriothallus sharonae provides an opportunity for comparison with modern liverworts. C_LIO_LIShale samples were collected and the carbonaceous fossils isolated by acid maceration. Museum shale specimens of Pallaviciniites devonicus were also obtained and processed. The relative location, composition, frequency and spatial distribution of the fossil dark cells was compared to that of oil cells in extant taxa. C_LIO_LIChemical characterization of the fossil dark cells is consistent with cells that contained lipids, the main component of oil bodies. Quantitative analyses revealed that the frequency and spatial distribution of dark cells are comparable to oil body cells. The dark cells of M. sharonae show clumping near the thallus edge, suggesting an anti-herbivore function. C_LIO_LIThese results support the hypothesis that the dark cells of Paleozoic liverworts and the oil body cells of extant lineages are homologous structures with a shared developmental origin, providing a new character that can be used to assign fossils and that sheds light on the evolution and function of liverwort oil bodies. C_LI

paleontology↗
bioRxiv2025

Hallucigenia's diet illuminates the feeding ecology of Cambrian lobopodians

The armoured lobopodian Hallucigenia sparsa embodies the seemingly uncanny nature of the animals that evolved during the Cambrian Explosion over 500 million years ago. Initially regarded as an evolutionary oddball, the exceptional preserved anatomy of H. sparsa has been substantially revised, leading to a better understanding of its relationships with other lobopodians and phylogenetic affinities with extant panarthropod phyla. However, the ecology and behaviour of H. sparsa remain largely enigmatic owing to the difficulties of interpreting its functional morphology and the perceived lack of modern analogues. Restudy of a composite fossil assemblage from the middle Cambrian Burgess Shale demonstrates swarm-like behaviour of several small H. sparsa individuals scavenging on a dead ctenophore. The lack of grasping, masticatory, or piercing mouthparts in H. sparsa points to suction feeding as a viable strategy to consume the gelatinous carcass. Reassessment of the morphology of H. sparsa reveals functional analogues shared with extant pycnogonids, including an elongate anterior end with a terminal mouth opening and enlarged foregut chambers lined up with sclerotized denticles. These observations suggest that suction feeding is ancestral for stem-group Onychophora and highlights the critical trophic role of small-bodied armoured lobopodians as degraders of soft-bodied carcasses in Cambrian benthic ecosystems.

paleontology↗
bioRxiv2026

Possible planktonic lifestyle of the Silurian trilobite Deiphon evaluated through 3D modelling

Zooplankton are a crucial part of modern oceans, feeding on primary producers and moving nutrients vertically and horizontally. Many euarthropods have evolved planktonic lifestyles, but evaluating extinct taxa were planktonic relies on documenting a broad distribution in diverse lithologies, occurrence across multiple paleobiogeographic regions, and morphological comparisons to modern analogues. Trilobites living in the water column have been proposed to take two forms, well-streamlined and poorly-streamlined, reflecting different lifestyles and behaviors in the water column. Both are believed to go extinct at the end of the Ordovician. A planktonic lifestyle was suggested for Deiphon based on its highly inflated, spherical glabella and reduced body, but this is not supported by recent workers. The purpose of the glabellar bubble is also debated, having been both suggested to store low density lipids to increase the buoyancy or host a highly expanded gut. We use a three-dimensional model of Deiphon to estimate volume and density of different tissue types (exoskeleton, gut, body, limbs) to calculate its specific gravity. To investigate the impact of the bubble and its contents, we tested the impact on buoyancy by varying presence of the inflated glabella, content of the bubble, and exoskeletal thickness. The sedimentological and geographical information for this animal is poor, making morphology the only proxy available to test its life mode. Exoskeletal thickness has a large impact on the buoyancy of Deiphon, suggesting plankton trilobites may have required thin exoskeleton to remain buoyant in the water. Our results support a pelagic lifestyle for Deiphon, if its bubble was filled with lipids, which we consider the most likely of the possibilities when the rest of the animals morphology is considered.

paleontology↗
bioRxiv2026

Experimental evidence for a microbial origin of reduction spots in red beds

Perseverance rover recently discovered sedimentary rocks reddened by ferric oxides and peppered with bleached spots lacking these oxides. Some of these spots are associated with phosphate, iron sulfide minerals, and organic matter, and are regarded as "potential biosignatures", suggestive of microbial iron-and sulfate-reduction and organic matter oxidation. Similar mm-cm-scale "reduction spots" occur in many ancient "red beds" on Earth. Although terrestrial reduction spots are widely considered biogenic, the available evidence is not decisive, and the proposed microbial mechanism of spot formation has not been tested experimentally. Here, we report a successful laboratory demonstration of bleached spot-formation in ferruginous sediment. Mm-cm-scale rounded bleached spots appeared within weeks on the underside of anaerobic sand-ferrihydrite slurries inoculated with mixed microbial communities obtained from the reducing zones of Winogradsky columns. The spatial and temporal distribution of observed bleaching events, which did not occur in sterile controls, are best explained by a microbially induced process, and DNA sequencing confirms that bacteria of iron-reducing genera are abundant in the bleached areas. These results strongly support the longstanding hypothesis that microbial colonies can indeed generate visibly bleached reduction spots in ferruginous sediments and rocks. Further experiments are needed to establish whether and how non-biological processes can mimic these features, and to search for features that disambiguate biogenic and abiogenic reduction spots.

paleontology↗
bioRxiv2026

Walrus Population-specific Marine Reservoir Offsets (ΔR) for Calibration of Radiocarbon Dates: Implications for Arctic Chronologies and Medieval Trade

Walruses have long played a vital role in Arctic subsistence and commercial economies, yet accurate radiocarbon dating of walrus-derived archaeological materials is complicated by regional variation in marine reservoir effects. This study presents new {Delta}R values derived from 31 new and 15 legacy radiocarbon dates on known-age walrus specimens spanning multiple populations of Odobenus rosmarus rosmarus and O. r. divergens. The results reveal substantial inter-population variability, with {Delta}R values ranging from -140 (Franz Josef Land) to +295 (Pacific), underscoring the importance of population-specific calibration. A pooled {Delta}R of +17{+/-}12 was calculated for western Greenland and the Canadian Arctic--regions central to the medieval Norse ivory trade--and applied to 12 walrus rostra and ivory artefacts excavated in Trondheim, Norway. The resulting calibrated dates are from the 11th to early 14th centuries CE, confirming that seemingly anomalous post-15th-century finds are residual rather than evidence of continued trade. An alternative {Delta}R estimate of -110{+/-}35, derived solely from archaeological context dates, suggests potential time lags between harvest and deposition. These findings demonstrate the value of known-age walrus {Delta}R data for refining chronologies of Arctic exploitation and long-distance trade, while highlighting the need for provenance studies in archaeological dating and both the pertinence and limitations of mollusk-based reservoir corrections.

paleontology↗
bioRxiv2026

Diverse megamammals exploited by humans, chronology and palaeoecology at Taima-Taima, Late Pleistocene, South America

The arrival of humans to the Americas at the end of the Pleistocene has been one of the foundations of the hypothesis that hunter-gatherer groups had a direct role in the extinction of megafauna. However, empirical evidence of the exploitation of megafauna by humans and associated chronological context are still scarce, especially in South America. Using evidence of modifications on osteological remains, we provide a reassessment of the megafauna that was exploited at the classic Taima-Taima site (Venezuela), with an updated chronology and paleoenvironmental inferences. Our results show that, at least, five species of extinct megaherbivores were probably exploited at the site, expanding the previous records, restricted to the proboscidean Notiomastodon platensis and the giant armadillo Glyptotherium cf. G. cylindricum. The new data of the other exploited taxa include the terrestrial sloth Glossotherium, the macrauchenid cf. Xenorhinotherium bahiense and a toxodontid; both killing and slaughtering activities were likely practised at the site. Seven new enamel radiocarbon dates show an age of 15.3-17.8 cal kyr BP for the fossiliferous strata, although this is likely to be a minimum age given the materials propensity for modern carbon uptake. The study of phytoliths and starch grains from the dental calculus of N. platensis identified five plant taxa from the phytoliths: arboreal dicotyledons, Poaceae, Marantaceae, Asteraceae and Arecaceae. Ecometrics studies of dental diversity reveal how no other single site on the continent preserves such a diversity of grazing and browsing megaherbivores exploited by humans.

paleontology↗
bioRxiv2026

The fossil record of siliceous sponge spicules can be taken at face value

Modern sponges (Porifera) diverged by the Cryogenian, but their silicious skeletons do not appear in the fossil record until one hundred million years later, a time-span termed the "spicule gap" and thought to be a taphonomic artifact even though sponges convergently evolved siliceous spicules. Due to sponges position in animal phylogeny and important role in regulating ocean chemistry, the timing of their biomineralization has major implications for the changing tempo and mode of Earth systems as animals radiate. In a comprehensive dataset of Ediacaran and Cambrian sponges, we find that spicules are readily preserved in Cambrian environments more extreme than those of the Ediacaran. Given the convergent evolution of siliceous spicules, we find that the fossil record accurately represents when spicules first evolved in the different sponge lineages.

paleontology↗
bioRxiv2026

Surface area calculations of lamellar support respiratory function of trilobite exopodites

Trilobites had biramous appendages with an inner endopodite (walking leg) and outer exopodite (gill) connected to the body through the protopodite (limb base). Whereas both endopodite and protopodite were involved in both locomotion and feeding, the exopodite has been subject to various functional interpretations including respiration, ventilation and swimming. Evidence from sites with exceptional fossil preservation indicate that trilobite exopodites show substantial variability in terms of the number and size of their articles, lamellae and setae, but the implications of this morphological diversity have never been investigated. Here, we created anatomically correct 3D models of exopodites in O. serratus and T. eatoni to calculate the SA of the lamellae and explore its relationship with body size. Our results indicate a large SA for O. serratus at 16,589 mm2 compared to the 2,159 mm2 for the much smaller T. eatoni. We also calculated lamellar SA for nine additional trilobite species with exceptionally well-preserved appendages based on lamellar measurements. The results indicate that lamellae SA of trilobites increased exponentially with overall body size. Trilobite data follows the same trendline of gill SA/biomass observed in extant species and thus supports the interpretation of their exopodites as respiratory structures despite substantial variation in morphology.

paleontology↗