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bioRxiv2025

Evolutionary implications of stipule occurrence in Permo-Carboniferous wetland forests dominated by Psaroniaceae

Stipules are specialized appendages borne at the leaf base with roles as diverse as sheltering of delicate growing tissues from environmental exposure, vegetative propagation and dispersal, and modification into climbing hooks or protective spines. Stipules are widely present in extant vascular plants, but their origins in geological history remain obscure and must have involved convergent evolution more than once, perhaps as early as the late Paleozoic emergence of forested terrestrial ecosystems. Based on extraordinary collections from the early Permian Wuda Tuff Flora, the earliest known stipule structure in the plant kingdom has been identified in marattialean tree ferns Psaroniaceae, the dominant element of Permo-Carboniferous wetland forests. Psaroniaceous stipules are consistent with protection of juvenile fronds and the stem apex as well as retention of a functional role in mature and withered fronds. Furthermore, the continued and perhaps indeterminate growth and the fully laminated stipules invite speculation of a potential role in vegetative propagation following detachment from the parent frond. However, no direct fossil evidence of stipules acting as vegetative propagules is currently available.

paleontology↗

bioRxiv2025

Limb proportions predict aquatic habits and soft-tissue flippers in extinct amniotes

IN BRIEFGordon et al. use a phylogenetic machine-learning approach incorporating linear and geometric morphometric analyses (including >11,000 original linear measurements) to characterize osteological correlates of interdigital webbing, soft-tissue flippers, and aquatic habits in amniotes. They find that relative hand length can reconstruct soft-tissue phenotypes and aquatic habits in extinct amniotes with >90% accuracy, enabling a more phylogenetically comprehensive investigation of limb evolution among bona fide aquatic and terrestrial species. This investigation reveals distinct morphometric landscapes for limb evolution in mammals and reptiles and clarifies the aquatic habits of multiple extinct groups with historically ambiguous ecologies. In addition, it debuts a versatile supervised machine-learning approach for reconstructing cryptic phenotypes from fossil material. O_FIG O_LINKSMALLFIG WIDTH=198 HEIGHT=200 SRC="FIGDIR/small/661573v1_ufig1.gif" ALT="Figure 1"> View larger version (83K): org.highwire.dtl.DTLVardef@38ca68org.highwire.dtl.DTLVardef@708fb4org.highwire.dtl.DTLVardef@1eaa6f6org.highwire.dtl.DTLVardef@7795c6_HPS_FORMAT_FIGEXP M_FIG C_FIG HIGHLIGHTSO_LIForelimb proportions reliably predict soft-tissue flippers and highly/fully aquatic habits with >90% accuracy across amniotes. C_LIO_LIInterdigital webbing cannot be predicted from the bones alone using previously suggested correlates. C_LIO_LIAll Paleozoic marine reptiles known to date lived at most an amphibious lifestyle, regularly voyaging onto land. C_LIO_LIPhylogenetic Receiver-Operating Characteristic (ROC) analysis effectively reconstructs cryptic phenotypes in extinct species. C_LI

paleontology↗

bioRxiv2025

Seed fossil record of Solanaceae revisited

The fossil record for Solanaceae has a complex taxonomic history, with many species originally described in the family being subsequently shown to belong in other plant families. In this work, we present an in-depth analysis of the nightshade seed fossil record, which corresponds to the largest amount of fossil material for the family despite having relatively few described taxa. We re-examined 110 fossil seeds previously assigned either to one of the six taxa or unplaced within the family. All fossils were imaged and measured for 14 discrete and continuous characters, and a subset of 22 well-preserved specimens was additionally subjected to micro-CT scanning. In parallel, we scored the same set of characters for seeds from 354 extant taxa of Solanaceae. We carried out a multivariate analysis of the combined extinct and extant dataset to visualize the placement of fossil seeds within Solanaceae seed morphospace. This analysis revealed a wide spread of fossils across morphospace, including a variety of shapes, sizes and testal wall features. For one fossil taxon (Hyoscyosperma daturoides Deanna & S.D.Sm. gen. et sp. nov.), the micro-CT images confirmed the presence of an elaiosome, otherwise only known in the family from the genus Datura L. Based on these analyses, we re-circumscribe three species and describe six new taxa (four in new genera), doubling the number of fossil seed species in the family. The broad geographic and stratigraphic distribution of these diverse taxa, from Eocene North America and Europe to Pleistocene Eurasia, support the notion that the Solanaceae is likely a family of a late Cretaceous origin that attained nearly a cosmopolitan distribution by the Eocene.

paleontology↗

bioRxiv2025

Hierarchical importance of factors impacting trilobite cephalic disparity

1Trilobite cephala show high disparity owing to their supporting of key functional ecological structures, such as sensory and feeding structures, and those enabling important behaviours like enrollment and exoskeleton moulting. Previous studies analysed associations between cephalic morphometry, trends through time and with diversity, and these behaviours. However, no studies have yet quantitatively compared the importance of these different varied factors on cephalic morphometry. Here, we explore the association between trilobite cephalic morphometry and taxonomic variables, moulting behaviour, and facial suture type in Principal Components Analysis morphospace, and assess whether these variables can predict cephalic morphometry using Linear Discriminant Analyses. We employed Linear Mixed-Effects Models (LMMs) to quantify the hierarchical importance of these variables for determining cephalic disparity. The dataset used comprises cephalon outlines for 762 species of trilobites from across the globe and through the entire Palaeozoic. We found that variation in cephalic morphometry is not clearly associated with moulting behaviour, nor is moulting behaviour linked to facial suture type. Trilobite moulting behaviour is evidently too phenotypically plastic, and/or preservationally impacted, to produce clear signals across broad datasets. Results demonstrate the utility of LMMs for palaeontological datasets; we found that family-level assignment overall well explains cephalic morphometry, more so than order-level assignment which shows significant overlap in morphospace. Geological Period, facial suture type, and moulting behaviour had little impact on cephalic morphometry. We thereby demonstrate that trilobite cephalic outline morphometry is generally in accordance with trilobite family-level systematics and highlight the use of LMMs for interrogating broad-scale fossil morphological data.

paleontology↗

bioRxiv2025

Temporal foundation model unveils ancient HepatitisB virus evolution

Since ancient hepatitis B virus (HBV) sequencing data are scarce and incomplete, the evolutionary dynamics of HBV have long remained enigmatic. This data gap hinders a comprehensive understanding of HBV genetic variations, evolutionary trajectories, and host interactions in different historical periods, preventing insight into its long-standing co-evolutionary relationship with humans. In this study, we developed a sequence-based generative foundational model, ViraChron (Viral Chronology Foundation Model), that integrates multi-scale temporal information to compensate for the lack of ancient HBV data. We confirmed the robustness of our model through sequence identity, phylogenetic, and recombination analyses. ViraChron enabled the identification of fixed mutations specific to HBV genotype A, demonstrating that HBV acquires survival advantages through mutations that are ultimately fixed by natural selection. Our model outperforms the original baseline in terms of sequence completion, achieving significantly higher accuracy. The model significantly reduced data acquisition time from 80 hours to 5.4 minutes per HBV genome, providing reliable, high-quality data for 7 new HBV genomes from specific archeological sites. ViraChron overcomes previous limitations, obtaining high-quality genomic data from samples over ten thousand years old, thereby facilitating a systematic understanding of viral evolution and its biological characteristics.

paleontology↗

bioRxiv2025

Locomotor Trends Among Early Mammals Illuminated by Predictors of Arboreality from the Mammalian Appendicular Skeleton

Arboreal locomotion is a common trait among extant mammals, and it likely evolved independently in numerous Mesozoic and Cenozoic mammalian lineages. We review evidence for the evolution of arboreality within lineages of early mammals and their stem relatives (Synapsida) while also emphasizing the uncertainty of locomotor inferences of fossil lineages. An improved understanding of the evolutionary origins and prevalence of arboreality in early mammals requires robust links between morphological traits and locomotor behaviors that can be applied to fossils. To this end, we use a large comparative dataset of linear measurements taken on extant mammalian postcranial specimens to evaluate the skeletal proxies that best differentiate arboreality from other locomotor modes. Consistent with previous research, we find that measures of digit length and elbow proportions are especially powerful predictors of climbing. Locomotor predictions based on single measurements or ratios are improved when phylogeny is incorporated into models. Nonetheless, combining multiple functionally relevant traits into our models yields robust predictions of locomotor mode even without incorporating phylogenetic information--this is especially encouraging for fossil groups with unstable phylogenies. We test these locomotor proxies in three early-mammalian case studies--Multituberculata, Plesiadapiformes, and early Theria. We find that multituberculates had a wide locomotor breadth whereas plesiadapiforms all had a high probability of climbing, consistent with previous studies. However, some Mesozoic therians in our sample are predicted to be ground-dwellers, conflicting with the hypothesis that the ancestral therian was scansorial or arboreal. The predictive tools presented here will improve locomotor inferences for small mammals, further illuminating the prevalence and importance of arboreality in early mammalian evolution.

paleontology↗

bioRxiv2025

Constraints and adaptations in crocodyliform skull evolution

Crocodyliformes display a diverse range of skull morphologies though their evolutionary history. Extant crocodilians possess platyrostral (broad and flat) snouts, thought to be sub-optimal for resisting feeding loads due to the conflicting demands of feeding and hydrodynamic constraints. In contrast, numerous Mesozoic crocodyliformes possessed oreinirostral (dome-shaped) skulls, were terrestrial and hence free from hydrodynamic constraint. This study aims to examine the role of function in determining skull shape in crocodyliformes, and assesses the difference in stress resistance between oreinirostral and platyrostral taxa. We hypothesise that in the absence of hydrodynamic constraints, oreinirostral taxa have skulls that are better suited for resisting feeding induced loads. Using finite element analysis (FEA), we evaluated biomechanical performance in oreinirostral notosuchian taxa Baurusuchus salgadoensis, Montealtosuchus arrudacamposi and Caipirasuchus paulistanus; compared to the extant platyrostral Alligator mississippiensis, Crocodylus niloticus, and Paleosuchus palpebrosus. Results show that oreinirostral morphologies are comparatively better suited for resisting forces generated during feeding, with increased muscular efficiency, supporting the hypothesis that hydrodynamic constraints influence crocodyliform skull evolution.

paleontology↗

bioRxiv2025

High precision CA-ID-TIMS U-Pb zircon age for the Dueling Dinosaur locality, with implications for regional correlation, basal age and duration of the Hell Creek Formation, Montana

Discovery of the spectacular Dueling Dinosaurs and other significant dinosaur localities from remote and isolated exposures of the Hell Creek Formation in central Montana highlight the complexity of establishing stratigraphic context and correlating Hell Creek Formation fossil localities located outside of the type area. This is particularly problematic for the lower two-thirds of the formation, which generally lacks reliable biostratigraphic or magnetostratigraphic zonation and has no dated ash beds. To address these enduring issues for one of the most significant Upper Cretaceous terrestrial fossil-bearing units in North America, detailed stratigraphic sections were established on the Murray Ranch and on McGinnis Butte in central Montana and correlated with other published Hell Creek Formation localities via magnetostratigraphy, biostratigraphy, and radioisotopic dating of ash beds. Results indicate that the K-Pg boundary is not exposed in the study area, however high-precision U-Pb CA-TIMS zircon ages for two newly discovered ash beds (66.929 {+/-} 0.020 Ma and 66.850 {+/-} 0.026 Ma, 2{sigma} internal uncertainties) bracketing the Dueling Dinosaurs locality provide the first absolute ages for the lower portion of the Hell Creek Formation, anywhere. Bayesian age-stratigraphic modelling places the Dueling Dinosaurs locality at 66.897 +0.023/-0.028 Ma and suggest that the age of the base of the formation is [~]67.102 +0.710/-0.173 Ma (or older) in the study area. Comparison of stratigraphic architecture within the study area with published sections in the type area suggests that named sandstone marker horizons used for lithostratigraphic and sequence stratigraphic correlation in the type area have limited utility for regional correlation and need to be used with caution.

paleontology↗

bioRxiv2025

Shell accumulation and taphonomic attributes of the stout razor clam Tagelus plebeius as indicator of environmental features in a South American coastal lagoon of international relevance.

The preservation of remains is conditioned by biotic and abiotic characteristics that are determined by the environmental conditions; thus, taphonomic analysis may indicate environmental features. Estuaries are priority areas due to their socio-ecological importance; however, they are at risk due to climate change and anthropogenic impacts. Bivalves are abundant in estuarine soft-bottoms and their remains may be valuable environmental indicators, since the biotic (e.g., life habits, mineral composition) and abiotic characteristics (e.g., tides or topography) lead to differences in the accumulation and preservation of their shells. Therefore, the objective of this work was to evaluate the accumulation and taphonomic aspects of modern shells of the stout razor clam Tagelus plebeius in relation to the topographic characteristics of intertidal areas in Mar Chiquita coastal lagoon (Buenos Aires, Argentina). The results would indicate remains transport to the intertidal areas with a low-energy dynamic. The topographic characteristics of the beaches combined with the pattern of shell accumulation, suggested that the remains transport is not due directly to topography but to a combination of factors. In fact, those factors related to beach localization with respect to the main water flow direction and hydrodynamics would be more relevant. Furthermore, the findings showed that the taphonomic attributes of deposited modern shells may indicate environmental characteristics, such as energy of transport, submersion time or predation pressure. This study showed the contribution that actualistic taphonomy research can make to understanding environmental characteristics and to diagnostics development for the management of these vulnerable and socio-economic important areas. Statements and DeclarationsThere is no competing interests related to this publication.

paleontology↗

bioRxiv2025

Study of the variability of Pterosaur tracks from the Jurassic and Cretaceous of Spain using geometrics morphometry: a new insight on their ichnotaxonomy and anatomical implications.

Pterosaur tracks are relatively abundant in the Spanish fossil record and are especially localized in the Upper Jurassic of the Asturian coast and in the Lower Cretaceous of the Cameros Basin. All cases so far have been identified within the ichnogenus Pteraichnus. The Berriasian of the Cameros Basin is especially abundant in pterosaur ichnites, and, for this reason, the presence of seven ichnogenera had been proposed, about which, in general, there has not been a complete consensus among researchers. These ichnogenera were established according to normal procedure in paleoichnology, that is, with morphological characters, as well as considering several variables and meristic indexes. We provide a study on the variability of pterosaur handprints, focused on the Cameros Basin record, using shape analytical tools (geometric morphometrics). The results suggest that shape variability is continuous with respect to pterosaur handprint geometry. In consequence, there are no distinctive features that allow us to discriminate between them, even considering factors such as geological age or geographical origin. The shape of pterosaur manus prints remains very constant, suggesting a conservative evolution pattern of the module formed by the digits I, II and III, an important structure of the pterosaur arm for adequate quadrupedal locomotion on land.

paleontology↗

bioRxiv2025

Foraminiferal environmental DNA reveals late Holocene sea-level changes

Reconstructing past relative sea level (RSL) provides critical insight into the mechanisms driving RSL change and informs future projections. Foraminifera are widely used sea-level indicators, but their application is often limited by poor preservation. Here, we demonstrate that foraminiferal environmental DNA (eDNA) and sedimentary ancient DNA (sedaDNA) provide a complementary approach to traditional morphological methods for RSL reconstruction. By analyzing surface sediments and a core from subtropical intertidal environments in the Pearl River Delta, we found that foraminiferal eDNA and sedaDNA assemblages exhibit clear vertical zonation, consistent with morphological results. An eDNA-based transfer function enabled high-resolution RSL reconstructions with decadal temporal and decimeter vertical precision from two periods: 290-1703 CE and 1956-present. Notably, eDNA preservation extended RSL reconstruction far earlier than morphological analyses (1956 CE). The eDNA reconstruction closely matched tide-gauge and geological RSL records, underscoring its potential as a robust tool for reconstructing past RSL and its driving mechanisms.

paleontology↗

bioRxiv2025

Ecological inference from isolated vertebrae: Evaluating functional signal across the carnivoran spine

Understanding the ecological adaptations of extinct species is a central goal in vertebrate palaeontology, but is often limited by the incomplete nature of the fossil record. While skulls and limb bones have traditionally been emphasized in functional and ecological reconstructions, vertebrae are frequently overlooked. While isolated vertebrae are among the most commonly preserved postcranial elements, they are rarely found as complete vertebral columns, raising the question of whether isolated elements alone can yield meaningful ecological information. In this study, we assess the potential of vertebral morphology to predict two key ecological traits, running speed and hunting mode, using three-dimensional geometric morphometrics across ten presacral vertebrae from a broad sample of extant carnivorans. We evaluate the predictive power of individual vertebrae, regional groupings (cervical, thoracic, lumbar), and multi-element combinations. Our results show that certain vertebrae retain strong ecological signals on their own, especially the first thoracic and lumbar elements. However, combining multiple vertebrae often dilutes ecological signal, likely due to their differing functional roles along the axial column. This highlights the importance of treating vertebral regions independently and suggests that single, strategically informative vertebrae may outperform multi-element approaches in some contexts. We apply this framework to the extinct dire wolf (Canis dirus) and find contrasting signals along the spine, the first thoracic and lumbar vertebrae suggest adaptations for faster locomotion, while some cervical vertebrae indicate an intermediate running speed. This mosaic supports the idea that C. dirus occupied a complex ecological niche involving both active predation and scavenging. These findings underscore the power of vertebral morphology for ecological inference in fossil taxa, particularly when remains are fragmentary, and argue for a more nuanced use of isolated axial elements in reconstructing extinct carnivoran behaviour.

paleontology↗

bioRxiv2025

New insights into the extinction and recovery of marine vertebrates across the Permian-Triassic mass extinction event in the Dolomites, Southern Alps, Italy

The impact of the Permian-Triassic mass extinction on marine vertebrates is poorly known due to their scarce fossil record. Here, we report Acrodus sp. [Chondrichthyes], Bobasatrania aff. ladina [Osteichthyes] and an indeterminate actinopterygian from the Changhsingian Bellerophon Formation, and a saurosphargid reptile from the lower Spathian Val Badia Member of the Werfen Formation in the Dolomites, Italy. The saurosphargid is represented by a single vertebra, whose relatively tall neural spine indicates that it might belong to a new species. This is one of the oldest Sauropterygomorpha records worldwide and the first unambiguous occurrence of Saurosphargidae in the western Paleo-Tethys during the Early Triassic. These new findings suggest fishes were more diverse in this paleo-tropical shallow shelf community of the western Paleo-Tethys in the latest Permian than during the Early Triassic. The evolution of the new apex predator niche (Saurosphargidae) relatively shortly after the mass extinction event coincides with the reappearance of predatory cephalopods and precedes the full ecological and taxonomic recovery of benthic groups in the Dolomites community. This contrasts with previous hypotheses about the delayed recovery of higher trophic groups. Furthermore, we dated a surface sample with actinopterygian scales found at a Permian-Triassic boundary outcrop. The U-Pb indicates 248+/-1 Ma as a maximum depositional age, and radiolarian biostratigraphy indicates an Anisian age. This suggests age assignments to surface samples require caution. U-Pb dating further reveals an age discrepancy in the scales and the host rock, likely due to 206Pb enrichment in scales during diagenesis.

paleontology↗

bioRxiv2025

Cretaceous crocodyliform reconciles conflicting evidence on the Mesozoic paleogeography of Europe during the Gondwana-Laurasia split

Inferred biotic exchanges between Europe and Africa during the Cretaceous have been used to support the hypothesis that the complete separation of Europe from Gondwana postdated the split of the remaining Laurasian landmasses from Gondwana. Under this framework, Europe, conceptualized as part of a proposed Eurogondwana, is thought to have maintained biogeographic connections with Africa well into the Cretaceous. A key piece of evidence underpinning this hypothesis has been the crocodyliform Doratodon carcharidens from the Late Cretaceous of Europe, previously interpreted as closely related to Gondwanan taxa. However, the material attributed to this species is fragmentary, and its skeletal anatomy--critical for phylogenetic inference--remains poorly understood. Here we describe a new partial skull of Doratodon carcharidens which represents some of the most complete material of Gondwanan taxa in the European Cretaceous. Our updated phylogenetic analysis unexpectedly and robustly places D. carcharidens among the Laurasian clade Paralligatoridae and reveals that morphological similarities to Gondwanan ziphosuchians, such as ziphodont dentition, are the result of ecomorphological convergence rather than shared ancestry. By reinterpreting the systematic position of further taxa representing biogeographic enigma, such as Ogresuchus furatus, our phylogeny implies a major role of the primary breakup of Pangea into Laurasia and Gondwana for crocodyliform divergence. A critical reassessment of the purported evidence for Gondwanan fish and tetrapod immigrants in Europe reveals that it is largely based on highly fragmentary and sporadic specimens, as well as weakly supported phylogenetic hypotheses. Given the sparse and uneven Jurassic and Cretaceous fossil record in both Europe and Africa, it remains plausible that taxa previously interpreted as Gondwanan dispersers instead represent vicariant relicts. Our results conflict with recent paleobiogeographic scenarios, highlight the absence of compelling evidence for the Eurogondwana hypothesis and instead support a primary Gondwana-Laurasia split.

paleontology↗

bioRxiv2025

Earliest Evidence of Elephant Butchery at Olduvai Gorge (Tanzania) Reveals the Evolutionary Impact of Early Human Megafaunal Exploitation

The role of megafaunal exploitation in early human evolution remains debated. Occasional use of large carcasses by early hominins has been considered by some as opportunistic, possibly a fallback dietary strategy, and for others a more important survival strategy. At Olduvai Gorge, evidence for megafaunal butchery is scarce in the Oldowan of Bed I, but becomes more frequent and widespread after 1.8 Ma in Bed II, coinciding with the emergence of Acheulean technologies. Here, we present the earliest direct evidence of proboscidean butchery, including a newly documented elephant butchery site (EAK). This shift in behavior is accompanied by larger, more complex occupation sites, signaling a profound ecological and technological transformation. Rather than opportunistic scavenging, these findings suggest a strategic adaptation to megafaunal resources, with implications for early human subsistence and social organization. The ability to systematically exploit large prey represents a unique evolutionary trajectory, with no direct modern analogue, since modern foragers do so only episodically.

paleontology↗

bioRxiv2025

Big Isotopic Data link millet consumption under Lombard rule in early medieval northern Italy

Archaeobotanical and biomolecular evidence from northern Italy has highlighted a significant increase in millet cultivation during the early medieval period. This study applies Bayesian spatiotemporal modelling to the Isotopia and CIMA databases, which collected isotopic measurements on bioarchaeological remains from ancient and medieval Europe, respectively, to investigate a debated historical link between this agricultural shift and the Lombard rule in northern Italy (568-774 CE). Results confirm that this period coincides with an increased reliance on millet, particularly in regions associated with the Po Valley. This shift is primarily attributed to the need for food security in a politically fragmented and unstable environment, with millet offering reliable yields due to its phenotypic traits for tolerance. While political agenda and environmental factors appear to impact millet cultivation to varying degrees, specific links with social or ethnic affiliations remain largely unclear and require additional research. The approach used in this study demonstrates the potential for Big Isotopic Data to identify major historical trends.

paleontology↗

bioRxiv2025

The oldest fossil record of a living true eel lineage (Protanguillidae, Anguilliformes) from Mexico reveals the gradual acquisition of modern eel traits

We present an integrative taxonomic study describing the first fossil representative of the family Protanguillidae from the Danian deposits near Palenque, Chiapas, Mexico. Osteological analysis and parsimony-based phylogenetic reconstruction using morphological characters support the designation of a new genus and species as a protanguillid by the presence of several features, including the autogenous premaxillae, the presence of metapterygoid and symplectic bones, the participation of pterosphenoid on the posterior margin of orbital margin, the reduced number of vertebrae, and the configuration of hypural complex. The new taxon differs from Protanguilla palau by the shape of last branchiostegal ray, the disposition of anterodorsal branch of subopercle, and the insertion of unpaired fins. To investigate the evolutionary history of true eels, we conducted a total-evidence tip-dating analysis combining 14 mitochondrial genes with a morphological matrix, incorporating both Cretaceous and Cenozoic fossil taxa. The results support a gradual acquisition of the diagnostic characters of Anguilliformes throughout the Cretaceous. A Bayesian topological test further supports the species here described as a surviving lineage of Cretaceous eels with {dagger}Libanechelyidae bultyncki, closely related to the modern eels. This discovery expands the paleobiogeographic range of the Protoanguillidae and provides new insight into the origin and diversification of true eels.

paleontology↗

bioRxiv2025

Mass Extinction Triggered the Early Radiations of Jawed Vertebrates and Relatives (Gnathostomes)

Most vertebrate lineages are first recorded from the mid-Paleozoic, well after their Cambrian origin and Ordovician invertebrate biodiversification events. This delay has been poorly understood and is usually attributed to sampling and long ghost lineages. We analyzed new databases of Paleozoic vertebrate occurrences, biogeography, and ecosystems, revealing that the Late Ordovician Mass Extinction (~444-443 million years ago) triggered parallel, endemic radiations of jawed and related jawless vertebrates (gnathostomes) in isolated refugia. Post-extinction ecosystems hosted the first definitive appearances of most major vertebrate lineages of the Paleozoic "Age of Fishes" (and today), following the loss of ubiquitous stem-cyclostome conodonts, nascent faunas of other gnathostomes, and pelagic invertebrates. Turnover and recovery patterns matched those following climatically similar events like the end-Devonian mass extinction, including a post-extinction "gap" with low biodiversity. The prolonged 23 million year Silurian recovery, and the challenges of oceanic dispersal, likely further delayed the dominance of jawed gnathostomes for millions of years after the first fossil jaws.

paleontology↗