The research, led by Zumin Xian, Qinyuan Xue, Yingtian Zhao, Qiang Li, and Min Zhu of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing and Qujing Normal University, is published in The Science of Nature. The team did not simply describe the external appearance of the fish. Because the specimens are articulated — meaning the bones are preserved in their life positions rather than scattered — the researchers were able to apply X-ray computed tomography, scanning the fossils layer by layer and then reconstructing the complete dermal head shield and trunk shield in three dimensions on a computer. This digital dissection revealed anatomical details that would be inaccessible on a crushed or partial specimen, including internal cavities, ridges, sensory canals, and the precise geometry of the plates that armored the animal’s face and torso.

To appreciate why this matters, it helps to understand what antiarchs actually were. They represent a highly specialized lineage of early jawed vertebrates that adapted to life on or near the sea floor, forming a major component of Devonian aquatic ecosystems. Unlike most placoderms, which had mobile neck joints allowing the head shield to lift during feeding, antiarchs evolved a rigid, box-like armor and relied on their modified pectoral appendages for locomotion and maneuvering over soft substrates. During the Middle and Late Devonian, euantiarchs achieved a nearly cosmopolitan distribution, with genera such as Bothriolepis turning up on every continent, including Antarctica. Their ubiquity makes them important index fossils for correlating Devonian rocks across the globe, and their abundance in some deposits suggests they formed dense schools in shallow waters, estuaries, and floodplains.

Yangfanyu anachoresis, however, is not just another euantiarch. In addition to displaying the diagnostic characters that define the group, the new fish retains several plesiomorphic — that is, ancestral or primitive — features that its later relatives had lost. Two of these are particularly significant: the cavity for the cranio-spinal process, an internal recess on the head shield that accommodated a bony projection from the trunk shield, and the oblique ridge on the lateral wall of the trunk shield. These features are hallmarks of more primitive antiarch lineages, such as the yunnanolepids that dominated Early Devonian faunas in South China. Their presence in Yangfanyu indicates that the earliest euantiarchs had not yet fully shed the anatomical baggage of their ancestors, providing paleontologists with a rare snapshot of a lineage caught in the act of transitioning from one body plan to another.

The phylogenetic analysis, which compiled a matrix of anatomical characters and ran them through the TNT software to generate an evolutionary tree, placed Yangfanyu at the most basal position among all known euantiarchs. In other words, it is the sister taxon to every other member of the clade — the earliest branch to split off from the euantiarch family tree. This placement is not merely a matter of adding one more twig to a branching diagram. Because Yangfanyu sits at the very base of the group, it refines what paleontologists call character polarity at the origin of the clade, clarifying which anatomical features were present in the common ancestor of all euantiarchs and which were acquired later. The result indicates that the characteristic euantiarch morphology — the distinctive head shield, the specialized pectoral appendages, the particular arrangement of trunk plates — was not assembled in a single evolutionary leap but rather through the sequential acquisition of derived characters during the earliest stages of euantiarch evolution.

This kind of finding is what evolutionary biologists refer to as a transitional form, and it is precisely the sort of evidence that can settle long-running debates about how major groups originated. For decades, the relationship between the primitive antiarch lineages of the Early Devonian and the highly successful euantiarchs of the Middle and Late Devonian has been murky, with gaps in the fossil record obscuring the sequence of anatomical changes. By extending the euantiarch record back into the Pragian, the new discovery narrows that gap and suggests that the morphological transition from primitive antiarchs to euantiarchs was underway by at least 410 million years ago, only a few million years after the first antiarchs appear in Silurian rocks.

The Guangnan locality itself is proving to be a treasure trove of Early Devonian vertebrates. The Posongchong Formation, which yields the new specimens, has previously produced a diverse array of early fish, including other placoderms and jawless forms, making it one of the most important windows into the earliest diversification of jawed vertebrates anywhere in the world. The new euantiarch adds to a growing list of discoveries from Yunnan Province that are reshaping our understanding of how the major jawed vertebrate lineages emerged and spread during the Devonian, a period sometimes called the Age of Fishes because of the extraordinary variety of aquatic vertebrates that flourished then.

What makes the discovery particularly compelling for a general audience is the sheer strangeness of the animals involved. Antiarchs are among the most morphologically bizarre of all placoderms, and their pectoral appendages — often described as fin-like or wing-like structures encased in bone — have been interpreted as adaptations for propping up the body, pushing along the substrate, or even digging into soft sediment. The fact that these appendages, along with the rest of the antiarch body plan, were already well established by the Pragian suggests that the ecological role of antiarchs as benthic specialists was in place very early in their history, long before they achieved their later cosmopolitan dominance.

The implications of the new study extend beyond antiarch phylogeny. Because euantiarchs are such abundant and widespread fossils, understanding their origins has knock-on effects for Devonian biostratigraphy — the business of using fossils to date and correlate rock layers. A 10-million-year extension of the group’s record means that euantiarch remains in rocks previously thought too old for the clade may need to be reinterpreted, and it raises the possibility that other early euantiarchs are waiting to be recognized in Pragian or even older deposits in South China and elsewhere. The researchers’ use of computed tomography and three-dimensional digital visualization also highlights a broader trend in vertebrate paleontology, in which digital dissection is revealing anatomical details that traditional preparation methods could never access, allowing paleontologists to reconstruct the complete anatomy of extinct animals from fragmentary or embedded fossils.

For now, Yangfanyu anachoresis stands as the earliest and most primitive known euantiarch, a 410-million-year-old armored fish from the riverbeds and shallow seas of what is now southwestern China. Its discovery extends the fossil record of one of the Devonian’s most successful vertebrate lineages by 10 million years, clarifies the sequence of anatomical changes that produced the classic euantiarch body plan, and adds yet another piece to the puzzle of how jawed vertebrates — the group that ultimately gave rise to sharks, bony fish, and every tetrapod, including humans — diversified during the earliest Devonian. As more specimens emerge from the Posongchong Formation and other Early Devonian localities in Yunnan, paleontologists expect the picture of antiarch origins to become even sharper, potentially revealing additional transitional forms that document the step-by-step assembly of one of the most distinctive body plans in the history of vertebrates.

Subject of Research: Paleontology

Article Title: The earliest euantiarch from the Pragian (Early Devonian) of Guangnan, Yunnan Province, China

Article References: Xian, Z., Xue, Q., Zhao, Y., Li, Q., & Zhu, M. (2026). The earliest euantiarch from the Pragian (Early Devonian) of Guangnan, Yunnan Province, China. The Science of Nature, 113(6), Article 134. https://doi.org/10.1007/s00114-026-02186-0

Image Credits: AI Generated

DOI: 10.1007/s00114-026-02186-0

Keywords: placoderms, Devonian, antiarchs, fossils, China, evolution, CT scanning, Yangfanyu, earliest, euantiarch, Pragian, Early

The road to this milestone was far from smooth. The early editors, Professor Gloria Arratia and Dr Dieter Korn, imposed exacting standards on article quality and impact at a time when the journal was still struggling to establish itself, and their persistence ultimately carried ‘Fossil Record’ into the Science Citation Index Expanded in 2014. The journal has maintained a tradition of publishing exclusively in English, releasing two volumes every year and subjecting every submission to the scrutiny of at least two international reviewers. More recently, it has embraced a fully open access model, a transformation supported by the museum’s Coordination Office for Scientific Publishing, which acts as a key driver of the institution’s Open Access strategy. The museum itself, through its Directorate General, has generously covered the author page charges, ensuring that financial barriers do not prevent researchers from sharing their findings with the global scientific community.

The choice of topic for the anniversary volume is no accident. The fish-to-tetrapod transition has a long and illustrious tradition at the Museum für Naturkunde, stretching back to Walter Gross (1903–1974), the eminent palaeoichthyologist and histologist who discovered and first described the Devonian tetrapod-like fish Panderichthys rhombolepis. The holotype of this pivotal species, a creature perched on the evolutionary branch leading from lobe-finned fishes toward the first four-legged land animals, is still kept at the museum. Hans-Peter Schultze and his working group continued Gross’s work and expanded its scope, publishing important new findings on Elpistostege, a relative of Panderichthys that sits even closer to tetrapods on the tree of life, and investigating the phylogenetic status of tetrapods as a monophyletic group as well as the environmental conditions that accompanied the transition from water to land.

That institutional tradition also owes much to a remarkable series of visiting researchers. Michel Laurin worked at the museum from 1997 to 1998, and Rainer Schoch from 2001 to 2002, both of whom went on to become distinguished figures in early tetrapod research. Today the baton is carried by the research groups led by Nadia Fröbisch and Florian Witzmann, whose primary focus is on temnospondyl amphibians, an extraordinarily successful and long-lived group of ancient amphibians that flourished for well over 100 million years. The special issue that emerges from this lineage is both a celebration of a journal and a showcase of how a single research institution can shape a field across generations.

Why does vertebrate terrestrialization continue to fascinate scientists and the public alike? Following the conquest of land, vertebrates evolved a remarkable diversity of body proportions and a wide array of feeding, locomotory and sensory adaptations, laying the foundations for every terrestrial ecosystem that exists today. Early tetrapods illuminate the rise of those ecosystems and reveal the deep roots of much of modern terrestrial vertebrate diversity, from amphibians and reptiles to birds and mammals. And because the emergence of four-limbed, air-breathing animals from aquatic ancestors is one of the major evolutionary transitions in the history of animal life, every new discovery in this field is, in a very real sense, a discovery about our own remote ancestry. It is this combination of scientific depth and visceral human relevance that makes early tetrapod research so compelling.

The special volume opens with a welcoming address by Professor Johannes Vogel, Director General of the Museum für Naturkunde, followed by a personal account from Hans-Peter Schultze of the journal’s founding in 1998 and the considerable difficulties it faced in its early years. The scientific core consists of eight original research articles written by 18 international authors, ranging from established leaders to young researchers at the start of their careers. Together, the papers span the palaeoecology of the fish-tetrapod transition, the morphology and phylogeny of stem tetrapods, the evolutionary history of temnospondyls, the convergent simplification of the tetrapod skull, and the biomechanics of skull construction in semi-aquatic and fully terrestrial tetrapods.

The first research article tackles a question that has long divided the field: where did tetrapods actually originate? By analogy with modern amphibians, most researchers had assumed that early tetrapods lived in freshwater environments, had evolved from fish-like ancestors there, and were unable to tolerate brackish or marine conditions. Michel Laurin challenges this orthodoxy. Building on a vast compendium of data and a sweeping literature survey, and expanding on his earlier 2010 study with Rodrigo Soler-Gijón, Laurin follows multiple independent lines of evidence to show that many early tetrapods were euryhaline, meaning they could tolerate a wide range of salinities, and lived in brackish waters or even fully marine settings. His striking conclusion is that tetrapods originated in marine environments, overturning a century of assumptions drawn from the biology of today’s frogs and salamanders.

The second article addresses one of palaeontology’s most notorious mysteries: Romer’s Gap. The first body fossils of limbed stem-tetrapods appear in the Late Devonian, yet during the first 15 million years of the subsequent Carboniferous Period, the Tournaisian and parts of the Viséan, tetrapod remains are exceedingly rare worldwide, a puzzling hiatus that gives the interval its name. In recent years, new finds from Scotland and Canada have begun to close this gap, and Tim Smithson and Marcello Ruta, together with the late Jenny Clack, redescribe one of these newly discovered Tournaisian tetrapods, Ossirarus kierani from Scotland. The animal displays a striking mosaic of primitive and derived characters, and the authors’ phylogenetic analyses strengthen the hypothesis that the morphological and taxonomic diversity of early tetrapods in the lowermost Carboniferous was far greater than previously assumed.

Several papers in the volume probe the astonishing experimentalism of early tetrapod evolution. Kim Kean, Marylène Danto, Celeste Pérez-Ben and Nadia Fröbisch survey the multiple groups of tetrapods that independently reduced and lost skull roof bones, attaining a simpler cranial architecture than that of tetrapodomorph fishes and various Devonian and later Palaeozoic relatives. Intriguingly, the loss of individual bones proved highly variable and could not be correlated with any particular lifestyle or body size, suggesting complex morphogenetic patterns that remain poorly understood. Ralf Werneburg and Florian Witzmann then turn to the eryopids, a diverse group of Permo-Carboniferous temnospondyls that had shifted from a strictly aquatic existence to a more amphibious mode of life. Their detailed redescription of three enigmatic Middle Permian taxa from Russia, Clamorosaurus borealis, C. nocturnus and Syndyodosuchus, combined with a comprehensive phylogenetic analysis, finds no support for the earlier view that these Russian eryopids were terrestrial, and instead argues that a semi-aquatic lifestyle is more probable.

The remaining contributions extend this story across the Triassic world and into the mechanics of the skull itself. Raphael Moreno, Sanjukta Chakravorti, Samuel Cooper and Rainer Schoch document a surprisingly rich diversity of temnospondyls from the partially marine Grabfeld Formation of southwestern Germany, straddling the Ladinian-Carnian boundary, including the oldest known metoposaurid and evidence that many members of the group were euryhaline despite arid sabkha and playa conditions. Rainer Schoch, Florian Witzmann, Raphael Moreno, Ralf Werneburg and Eudald Mujal describe for the first time the ontogeny of the largest known temnospondyl, the giant capitosaurian Mastodonsaurus giganteus from the Middle Triassic of Germany, using skulls ranging from just 12–15 millimetres to a colossal 1200 millimetres; unlike Palaeozoic forms, which had salamander-like larval phases, Mastodonsaurus attained its adult morphology early in development, revealing a major shift in developmental mode. Pummy Roy, Sanjukta Chakravorti and Dhurjati Prasad Sengupta newly document the anatomy of the giant Indian capitosaur Cherninia denwai, an apex predator from the Middle Triassic Denwa Formation, including postcranial bones described for the first time. Finally, Ingmar Werneburg offers a new biomechanical hypothesis for the evolution of cranial openings such as temporal fenestrae and palatal vacuities, showing that their formation or closure correlates tightly with bite force exerted by the jaw adductors, with the presence of cranial weapons such as horns and frills, and even with stresses induced by the neck musculature. Together, these studies honour a quarter century of ‘Fossil Record’ while charting the future of research into the greatest migration in vertebrate history.

Subject of Research: The 25th anniversary of the journal Fossil Record and a special issue on the fish-to-tetrapod transition and early tetrapod evolution

Article Title: Editorial: 25 years of ‘Fossil Record, an International Journal of Palaeontology’

Article References: Witzmann, F., Ruta, M., Fröbisch, N., Paß, S., & Herrmann, E. (2024). Editorial: 25 years of ‘Fossil Record, an International Journal of Palaeontology’. Fossil Record, 27(3), 291-293. https://doi.org/10.3897/fr.27.143987

Image Credits: AI Generated

DOI: 10.3897/fr.27.143987

Keywords: Fossil Record, palaeontology, tetrapods, fish-to-tetrapod transition, temnospondyls, Museum für Naturkunde, Romer's Gap, Devonian, Carboniferous, Triassic, skull biomechanics, open access

Bothriolepis is, by any measure, a superstar of Devonian paleontology. With 97 recognized species, it is the most speciose genus among the antiarchs, a highly specialized group of placoderms, the jawed stem gnathostomes that dominated the waters of the Silurian and Devonian worlds. Antiarchs are instantly recognizable by their heavy bony armor and paired pectoral appendages that resemble jointed arms encased in plates. Sixty-five genera of antiarchs have been reported so far, and Bothriolepis stands out not only for its diversity but also for its cosmopolitan distribution, with fossils recovered from every major Devonian landmass. Yet despite this fame, many of its species remain known from frustratingly incomplete material.

B. yunnanensis is a case in point. Liu described the species in 1962 based on an anterior median dorsal plate and an incomplete posterior median dorsal plate collected from a small hillside about one kilometer north of Zhanyi Old Town, now the Taojiashan area of the Zhanyi urban district. These plates come from the Middle Devonian Shangshuanghe Formation, which is characterized by yellow to green fine-grained sandstones yielding abundant disarticulated fish plates. Although the species has been frequently cited in stratigraphic studies over the decades, no additional material had ever been described, leaving its morphology and phylogenetic position poorly understood. The new study designates the anterior median dorsal plate as the lectotype and the posterior median dorsal plate as the paralectotype, formally anchoring the species to a single anatomical reference point.

Everything changed with continuous fieldwork that began in 2020. The research team collected numerous new specimens from the type locality and from two sites in the Zhujiangyuan area, designated Zhujiangyuan Locality 1 and Zhujiangyuan Locality 4. The haul includes an articulated head shield, a head shield articulating with the trunk armor, pectoral appendages, and many disarticulated plates. All specimens are housed in the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences in Beijing. The fish-bearing layer at Zhujiangyuan Locality 1 belongs to the Shangshuanghe Formation of Eifelian age, while the layers at Zhujiangyuan Locality 4 belong to the Xichong Formation of Givetian age. This new fossil horizon extends the temporal range of B. yunnanensis from the Eifelian to the entire Middle Devonian, a significant expansion for a species previously known from a single horizon.

The Devonian strata of the Qujing area are exceptionally well exposed and subdivided into a clear succession of formations, from the Lower Devonian Xishancun, Xitun, Guijiatun, and Xujiachong formations, through the Lower to Middle Devonian Chuandong Formation, the Middle Devonian Shangshuanghe and Xichong formations, and up to the Upper Devonian Zaige Formation. In the Zhujiangyuan area, the Guijiatun, Xujiachong, and Chuandong formations are absent, and the Middle Devonian units sit directly between the underlying Lower Devonian Xitun Formation and the overlying Upper Devonian Zaige Formation. At Taojiashan, the limited fish-bearing Middle Devonian is strictly controlled by faults, but lithological characteristics and available biostratigraphic evidence assign the lectotype horizon to the Shangshuanghe Formation.

The technical heart of the study lies in the detailed description of the newly recovered material, including high-resolution computed tomography of a well-preserved head shield. The head shield of B. yunnanensis is wider than long, with a breadth to length ratio of 1.35 in the largest specimen, which measures 77 millimeters across. The orbital fenestra, the window for the eyes, is short and wide with a breadth to length ratio of 2.1, and its anterior margin is concave while the posterior margin is straight. The premedian plate is trapezoidal, the lateral plate is the largest plate of the head shield, and the postpineal plate is wider than long, shaped as a posteriorly pointing rounded triangle. The nuchal plate is roughly heptagonal, and its anterolateral margin is obviously shorter than its posterolateral margins, a subtle but diagnostic feature.

The CT scan of specimen IVPP V34361, performed on a GE v|tome|x micro-tomography scanner at 240 kV and 110 mA with a resolution of 59.963 micrometers, produced 3,979 slices that were segmented and reconstructed in three dimensions. The visceral surface of the head shield revealed a trifid preorbital recess with three well-developed extensions, a developed postorbital process, a well-developed paramarginal crista in the otico-occipital depression, and a low and broad transverse nuchal crista. Crucially, the large unpaired insertion fossa for levator muscles lies immediately behind the transverse nuchal crista, and there is no median occipital crista. This absence of the median occipital crista is one of the key characters that unites B. yunnanensis with a distinctive clade of Bothriolepis species.

The trunk armor tells an equally detailed story. The anterior median dorsal plate is hexagonal with anterior and posterior margins nearly equal in width, and its breadth to length ratios range from 0.82 to 0.91 across the studied specimens. The ratio between the breadth of the anterior margin and the maximum breadth of the plate ranges from 0.43 to 0.53, well below the 0.55 threshold that separates B. yunnanensis from its closest Chinese relatives. The levator fossa is a broad and short inverted triangle occupying one-third of the plate length, and the anterior ventral pit lies posterior to the confluence of the postlevator thickening and postlevator cristae. The posterior median dorsal plate is pentagonal with an arc-shaped posterior margin lacking a posterior corner, and the ventral median groove on its ventral side is absent. The pectoral appendage is remarkably slender, with a proximal segment reaching 87.2 millimeters in length but only 19.4 millimeters in breadth in the largest specimen, an elongation ratio of 4.49, and short, blunt, closely arranged lateral spines run along its margin.

With this comprehensive morphological dataset in hand, the team conducted a parsimony phylogenetic analysis based on the data matrices of previous studies, adding B. yunnanensis as a new taxon and one additional character. The analysis yielded 12 most parsimonious trees, each with a length of 385 steps, a consistency index of 0.213, and a retention index of 0.498. The results place B. niushoushanensis at the most basal position within the genus, while B. yunnanensis, B. zhujiangyuanensis, B. sinensis, and B. kwangtungensis from China form a clade with some Bothriolepis species from Laurussia and Kazakhstania. This clade is supported by three synapomorphies: the absence of the median occipital crista, a slender proximal segment of the pectoral appendage, and a long posterior pit line. The trifid shape of the preorbital recess appears very low in the phylogeny, consistent with recent computerized analyses but contradicting older interpretations.

The paleogeographic implications are perhaps the most thrilling part of the story. During the Devonian, the South China and Kazakhstania blocks were separate terranes, and the presence of shared Bothriolepis clades between China, Kazakhstania, and Laurussia suggests faunal connections among these regions. The new analysis further corroborates the paleogeographic proximity between the South China and Kazakhstania blocks, reinforcing a picture of Devonian seas and coastlines that were far more connected than their modern geography might suggest. Meanwhile, B. tungseni from China emerges as the sister taxon of B. dorakarasugensis from Siberia, adding another thread to this transcontinental web. For a species that sat in taxonomic limbo for more than sixty years, B. yunnanensis has now become a bridge between continents, a reminder that even the most fragmentary fossils can hold the keys to understanding how life spread across an ancient planet.

Subject of Research: Paleontology

Article Title: Morphology and phylogeny of Bothriolepis yunnanensis ( Placodermi , Antiarcha ) from the Middle Devonian of China

Article References: Yan, Y., Zhao, W., Luo, Y., Yu, H., & Zhu, M. (2026). Morphology and phylogeny of Bothriolepis yunnanensis (Placodermi, Antiarcha) from the Middle Devonian of China. Swiss Journal of Palaeontology, 145, 535-551. https://doi.org/10.3897/sjp.145.179243

Image Credits: AI Generated

DOI: 10.3897/sjp.145.179243

Keywords: Bothriolepis, placoderm, Devonian, antiarch, paleontology, China, fossil fish, phylogeny, Morphology, yunnanensis, Placodermi, Antiarcha

The significance of the new material lies in what it preserves. The original diagnosis of Malongia was based on an incomplete specimen preserved in ventral aspect from the Xiaxishancun Formation of Yunnan, which left the animal’s dorsal anatomy largely unknown. The two newly described individuals, however, preserve the carapace and dorsal exoskeletal structures, features that are incompletely preserved or absent in the original type material. One individual is preserved in dorsal view, showing an incomplete carapace, partial swimming appendages and an articulated prosoma with eight tergites, while the other is preserved in ventral view, revealing the carapace outline, six pairs of proximal podomeres with associated appendages and an articulated opisthosoma composed of two ventral plates.

The dorsal-view individual measures more than 55.5 millimetres in preserved length, with a maximum width exceeding 22.3 millimetres at the third tergite. Its carapace, incompletely preserved at more than 14.3 millimetres long and 15.7 millimetres wide, is fringed by a narrow marginal rim roughly 3 millimetres wide bearing coarse surface ornamentation. Crucially, the right lateral compound eye is intact: relatively large, up to 4.6 millimetres long and 2.3 millimetres wide, arcuate with rounded extremities, covered dorsally by a well-developed rounded palpebral lobe and occupying an anteromesial position on the carapace. A median ridge runs along the centriaxial region of the carapace, and each opisthosomal tergite carries a row of tubercles along its posterior margin. These details, invisible in the holotype, form the raw material for a systematic revision of the genus.

The ventral-view individual is equally informative. Its carapace outline, traced from the impressed carapace trace, is distinctly horseshoe-shaped, with a gently convex frontal margin and a narrow marginal rim approximately 2 millimetres wide. The prosomal appendages are preserved exclusively on the left side, but their coxae exhibit only slight torsion while retaining their relative spatial arrangement, allowing unambiguous identification of each appendage. Appendages I and II are known only from small subrectangular proximal podomeres, while appendages III, IV and V preserve pairs of coxae and several rectangular podomeres of nearly uniform width. Appendage VI, the swimming paddle, preserves a pair of subrhomboidal coxae and two podomeres, expanding gradually in width from proximal to distal end. The coxal gnathobase bears a row of triangular teeth, and although the principal tooth is absent, the preserved morphology indicates that it would have been larger than the other teeth.

Perhaps the most consequential ventral feature is the slender, type-A genital appendage, partially preserved on the median portion of the second ventral plates and extending to their posterior margin with a total length of 6.2 millimetres. The ventral plates themselves are splayed open, forming an aperture of two symmetrical, unconnected elements. This configuration initially invited comparison with the Megalograptus morphotype, but the authors caution that eurypterid carapaces are susceptible to cracking during moulting and that the ventral plates on both sides show evidence of folding, so assignment to the Megalograptus type may not be accurate. Following the taxonomic treatment of Lamsdell, the specimens are instead assigned to the Eurypterus-type ventral plates, a decision that carries real weight in phylogenetic character coding.

The horseshoe-shaped carapace of the new specimens differs from that of the holotype, but the discrepancy is interpreted as the result of taphonomic distortion affecting the original type material. The new individuals, preserved in flattened siltstone with some tectonic distortion, likely represent the natural carapace morphology of Malongia mirabilis. On this basis the authors present an emended diagnosis of the genus: a dolichopterid with a horseshoe-shaped prosomal carapace, genal facets continuously inclined towards the carapace centre, prosomal ventral plates of Eurypterus type, arcuate lateral eyes positioned anteromesially on the carapace, spiniferous Dolichopterus-type appendages I to IV, a non-spiniferous Dolichopterus-type appendage V, and a moderately expanded paddle of regular Dolichopterus type on appendage VI, together with a lyrate metastoma.

To assess where Malongia sits relative to other dolichopterids, the team re-coded morphological characters following the standardised trait definitions and scoring criteria established in a recent revision of the family, supplementing the existing character matrix with the newly recognised dorsal and ventral features. Phylogenetic inference was performed in TNT v.1.5 using 100,000 replicates of random addition sequence followed by tree bisection-reconnection branch swapping, with all characters treated as unordered and equally weighted. Strobilopterus laticeps served as the outgroup taxon for tree rooting and character polarisation across the Dolichopteridae, establishing ancestral character state distributions for comparative evolutionary analysis.

The recovered topology reshapes the picture of dolichopterid evolution. Paraeurypterus anatoliensis and Pentlandopterus minor form successive early-diverging lineages, branching sequentially before the origin of a clade containing all remaining sampled dolichopterid species. Within that core clade, the position of Malongia is affected by a polytomy: its relationships with Dolichopterus and with the clade comprising Ruedemannipterus and Clarkeipterus remain unresolved. Three equally plausible phylogenetic hypotheses are permitted by the data. Malongia could be the sister taxon to Dolichopterus, sister to the Ruedemannipterus and Clarkeipterus clade, or sister to both lineages combined. It is therefore not possible to confirm whether Malongia constitutes a distinct monophyletic subgroup, although the Dolichopterus assemblage and the Ruedemannipterus plus Clarkeipterus grouping each emerge as coherent subclades within the polytomy.

That uncertainty is itself scientifically meaningful. Previous work had recovered Malongia as the sister taxon to Dolichopterus, but the revised analyses, incorporating the newly described dorsal and ventral characters, instead support an alternative placement. The unresolved phylogenetic position, combined with the genus’s morphological apomorphies, is consistent with the hypothesis that the ancestral lineage of Malongia underwent geographically isolated evolution on the South China Block following its divergence from the common ancestor shared with the Dolichopterus lineage. The South China Block rifted away from Gondwana during the Late Silurian to Early Devonian, and such biogeographic isolation may have restricted gene flow between South Chinese dolichopterids and their closely related lineages distributed across Laurussia, facilitating the evolution of exclusive derived features and the origin of this independent evolutionary lineage.

The new material also strengthens the case for a long-lived palaeobiogeographic province on the South China Block during the Early Devonian. Both Malongia mirabilis and the eurypterid Pterygotus wanggaii, recovered from the Xitun and Xiaxishancun Formations, provide direct fossil evidence for a close faunal linkage between the two units in the Qujing area of eastern Yunnan. Identical ostracod assemblages, early vertebrate fish taxa and fragmentary primitive land plant remains are found in both successions, reflecting stable, homogeneous palaeoecological conditions without major faunal turnover across the formation boundary. The continuous depositional sequence and shared endemic eurypterid species indicate that the Xiaxishancun and Xitun Formations represent a single, long-lived province with unimpeded biotic exchange and sustained faunal continuity, a setting in which an isolated lineage like Malongia could evolve its own distinctive morphology while the rest of the dolichopterid family tree branched across Euramerica.

Subject of Research: Palaeontology

Article Title: New insights on the morphology and phylogeny of the Chinese dolichopterid eurypterid Malongia ( Eurypterida , Dolichopteridae )

Article References: Ma, Z., Zheng, Y., Wang, M., Lamsdell, J. C., Wang, J., Pang, L., Chen, L., Selden, P. A., Yuan, Y., Zeng, J., He, B., & Hu, X. (2026). New insights on the morphology and phylogeny of the Chinese dolichopterid eurypterid Malongia (Eurypterida, Dolichopteridae). Swiss Journal of Palaeontology, 145, 991-998. https://doi.org/10.3897/sjp.145.210382

Image Credits: AI Generated

DOI: 10.3897/sjp.145.210382

Keywords: eurypterids, sea scorpions, Malongia, Dolichopteridae, Devonian, Yunnan, phylogeny, palaeontology, insights, morphology, Chinese, dolichopterid

The research team, working at outcrops between 2021 and 2024, photographed, analysed and measured the specimens directly in the field, because the lithology and consistency of the host rock made collecting them impracticable. The traces are preserved in concave and convex epirelief, hyporelief and full relief within marly limestones of Eifelian and Givetian age, roughly 393 to 383 million years old. Two distinct ichnoassemblages emerged from the analysis. The Eifelian strata yielded Arenicolites isp., Crescentichnus antarcticus, Selenichnites hundalensis and Osculichnus cf. labialis, while the Givetian layers contain Arenicolites isp., Diplocraterion isp., Sinusichnus sinuosus and Thalassinoides paradoxicus.

The most eye-catching of these fossils are the crescentic and horseshoe-shaped impressions attributed to xiphosurans, the group of arthropods that includes modern horseshoe crabs. Remarkably, no xiphosuran body fossils have ever been found in Devonian deposits anywhere in Africa, yet the traces at Hamar Laghdad show exactly the kind of morphology that living limulids produce when they dig into the sea floor. Selenichnites hundalensis from the lower Eifelian consists of suboval depressions with paired crescentic lobes, faint segmentation, occasional scratch traces and, in some specimens, an elongate telson impression trailing behind. The new Moroccan material represents the oldest occurrence of Selenichnites in Gondwana and one of the oldest in the world, previously known only from Late Triassic strata.

Crescentichnus antarcticus, preserved as elongated crescentic depressions measuring 5 to 8 centimetres long and 7 to 11 centimetres wide, is interpreted as a prod trace made when a horseshoe crab’s prosoma touched the sediment at an angle, perhaps as the animal swam up from the sea floor or made rapid contact to catch prey. The study draws on decades of work on modern limulid burrowing, including Eldredge’s classic four-stage description of burial by downward flexion of the prosoma and promotor-remotor swings of the prosomal legs. Intriguingly, the co-occurrence of Crescentichnus, Selenichnites and the fish-jaw trace Osculichnus with dwelling burrows of Arenicolites on the same surfaces hints at a hunting and feeding relationship between the tracemakers and the burrow-dwelling worms or crustaceans below.

Osculichnus cf. labialis itself is a curiosity: a hypichnial bilobate mound whose two lip-like lobes reflect the outline of upper and lower jaws. Such traces are usually attributed to jawed fish that plunged vertically or obliquely into the sediment to seize prey. The Hamar Laghdad specimen, with a larger lobe 20 millimetres wide and a smaller one 10 millimetres wide, separated by an undulate furrow with a small central knob, is the first record of this poorly known ichnogenus from the Middle Devonian of Africa, adding a predatory fish to the cast of characters roaming the Devonian shelf.

The Givetian assemblage tells a different story, one of complex engineering. Sinusichnus sinuosus consists of regular to slightly irregular sinusoidal tunnel systems with smooth, unlined walls, predominantly horizontal, and branching at triple junctions in Y-shaped and occasionally T-shaped patterns, with branch angles between 112 and 125 degrees. Tunnel diameters range from 1 to 2 centimetres, meander amplitudes from 4 to 8 centimetres and wavelengths from 10 to 20 centimetres, with individual systems locally exceeding 60 centimetres in length. The new Moroccan material is currently the oldest known occurrence of this ichnospecies in Gondwana, and the first evidence of the ichnogenus in Africa.

Even more striking are the burrow networks of Thalassinoides paradoxicus, which in the upper Givetian carbonates surround and converge upon the shells of dead cephalopods, including oncocerids, orthocerids and multilobate pharciceratid and beloceratid ammonoids. The burrow fill, a brown, very fine-grained clayey to marly carbonate, contrasts sharply with the grey to black host rock. The researchers propose an exceptional feeding strategy: after the cephalopods died and their soft parts decayed, the carcasses became nutrient sources, microbes colonised the organic compounds, and the Thalassinoides tracemakers exploited the biofilm inside the body chambers and around the conchs through conveyor-belt feeding. To the authors’ knowledge, no similar association of body fossils surrounded by such complex burrow systems has been reported before.

Because Palaeozoic burrow systems assigned to Thalassinoides predate the callianassid shrimps that construct similar burrows today, the Devonian tracemakers must have been non-callianassid crustacean arthropods or trilobites. Likewise, the Sinusichnus producers are proposed to be eumalacostracan crustaceans, whose segmented abdomens would have permitted the sinuous movements recorded in the burrows. The study observes gradual transitions between Sinusichnus and Thalassinoides in the same strata, suggesting that the tracemakers shifted between feeding strategies, from fodinichnia to domichnia. Taken together, these traces suggest that the complex burrowing, navigational and scavenging behaviours of modern arthropods have far more ancient roots than previously thought.

The trace fossils also encode a detailed record of environmental change. During the Eifelian, the Tafilalt Platform was a pelagic submarine high with very slow carbonate sedimentation, producing condensed nodular limestones and marls rich in ammonoids such as Fidelites, Foordites and Pinacites. The ichnofauna of that interval, combining fodinichnial traces like Crescentichnus and Selenichnites with vertical dwelling burrows of Arenicolites, belongs to the Skolithos-Cruziana ichnofacies and points to a moderately shallow inner shelf with high hydrodynamic energy, well-oxygenated water and abundant organic matter. By the Givetian, deposition took place in somewhat deeper settings, still on the shelf, with alternating calm and energetic conditions recorded by the co-occurrence of horizontal and vertical burrows.

This sea-level rise on the inner shelf of an epicontinental sea at the northwestern margin of Gondwana was shaped by peculiar local conditions. The more than 40 conical Kess-Kess mud-mounds of late Emsian age, distributed over 7 kilometres, created a palaeotopography that controlled sedimentation and ecosystem conditions long after the mounds stopped growing, generating diverse microenvironments with varying water depth, energy, sediment accumulation and light availability. The region’s famous palaeobiodiversity, it turns out, includes not only the skeletal record of ammonites, bivalves and brachiopods but also this hidden archive of behaviour. The abundance and variety of both trace and body fossils strongly encourage further systematic prospecting at Hamar Laghdad, where the Devonian sea floor may yet surrender more stories written not in bone but in burrow.

Subject of Research: Middle Devonian ichnofossils from Hamar Laghdad (eastern Anti-Atlas, Morocco)

Article Title: Middle Devonian ichnofossils from Hamar Laghdad (eastern Anti-Atlas, Morocco)

Article References: Bel Haouz, W., Lagnaoui, A., Klug, C., Baidder, L., & Maanan, M. (2026). Middle Devonian ichnofossils from Hamar Laghdad (eastern Anti-Atlas, Morocco). Swiss Journal of Palaeontology, 145, 403-431. https://doi.org/10.3897/sjp.145.188799

Image Credits: AI Generated

DOI: 10.3897/sjp.145.188799

Keywords: Devonian, ichnology, trace fossils, Morocco, Anti-Atlas, paleontology, xiphosurans, horseshoe crabs, arthropods, Hamar Laghdad, Middle, ichnofossils

The research, led by Dana E. Korneisel of Carleton University and Uppsala University together with colleagues in Canada and the United States, set out to test a hypothesis that has circulated in vertebrate palaeontology for decades. Because the skulls of stem tetrapods such as Acanthostega and Tiktaalik became decoupled from the pectoral girdle, many researchers inferred that neck mobility must have increased markedly during the origin of tetrapods, potentially facilitating the ecological transition toward more terrestrial habitats. What the hypothesis lacked was a functional test, and the reason is anatomical: the vertebral components of these ancient animals were incompletely co-ossified, making their mechanical behaviour extraordinarily difficult to model from fossils alone.

The problem stems from how the axial column was built in these creatures. Stem tetrapods retained a notochord-dominated spine into adulthood, a condition inherited from their lobe-finned fish ancestors. The notochord, a fluid-filled rod of soft tissue, was surrounded by cartilaginous or bony arches that lacked bone-to-bone joints. This arrangement predates the rigid vertebral column of most modern tetrapods, in which bony centra fuse to neural arches and vertebrae articulate through inter-central and zygapophyseal joints. No living tetrapod has an anatomically or functionally comparable axial skeleton, so the team had to look elsewhere for a testable analogue.

They found it in an unexpected place: the lake sturgeon, Acipenser fulvescens. Although sturgeon are ray-finned fishes only distantly related to tetrapods, they independently retained an intact notochord into adulthood, and their body dimensions closely match those of stem tetrapods. The proportions of vertebral arches to the notochordal canal in cross-section are strikingly similar, and the arches are joined by unmineralized connective tissue rather than zygapophyseal joints, just as in the extinct forms. The researchers acknowledge some differences—sturgeon possess supraneurals, and their basidorsals and basiventrals are positioned dorsoventrally across the notochord, whereas the intercentra and pleurocentra of stem tetrapods are staggered ventrolaterally—but the overall mechanical configuration is close enough to serve as a calibrated model.

The team performed a series of material tests on ten sturgeon specimens using a ZwickiLine materials testing machine. Three-point bending trials measured lateral flexion stiffness and extension stiffness, while torsion trials quantified rotational stiffness. Crucially, they tested both the isolated notochord and the whole axial column with its mineralized arches and connective tissues intact. The results were unambiguous: the whole column was considerably stiffer than the notochord alone, and this high stiffness could not be attributed to hard stops or joint interactions between the arches, which the researchers did not observe during testing. Only negligibly small forces and torques were needed to bend and twist the bare notochord. In other words, the surrounding tissues—not the notochord itself—dominate the mechanical behaviour of the column.

Applying these measured stiffness values to the reconstructed axial columns of six fossil taxa, the team produced striking estimates. For five stem tetrapods—Eusthenopteron foordi, Tiktaalik roseae, Acanthostega gunnari, Whatcheeria deltae and Greererpeton burkemorani—plus the early crown tetrapod Trimerorhachis insignis, they calculated the forces required to bend the neck and the muscle cross-sectional areas available to generate those forces, capped at half the area of an oval fitted around the occiput. The verdict: most stem tetrapods could move their heads less than 6 degrees laterally and less than 3 degrees dorsally, and could not rotate them at all. Eusthenopteron managed an estimated 8.5 degrees of lateral flexion and Tiktaalik 5.5 degrees, while Acanthostega, Greererpeton and Trimerorhachis showed even lower values, below 3 degrees of lateral flexion and under 1.5 degrees of extension.

Rotation proved even more prohibitive. Using the torsional rigidity of the sturgeon column and the polar moments of area of the fossil vertebrae, the researchers calculated the torque needed for even a modest 5-degree head turn. Tiktaalik required the least, at roughly 200 newton-metres, while all other taxa needed between 314 and 746 newton-metres—enormous figures given the short lever arms formed by the cervical ribs and associated musculoskeletal elements. Even Greererpeton, which possesses distinct atlas and axis vertebrae, could not plausibly have rotated its head. Large head turns, the model suggests, were simply infeasible across the entire tetrapod stem.

One taxon stands out as an exception. Whatcheeria, with a neck measuring nearly 20 centimetres or 89 percent of its skull length, could achieve an estimated 32 degrees of lateral flexion and 12 degrees of extension—roughly tenfold and eightfold higher, respectively, than other early tetrapods. The explanation lies in the physics of beam bending: the force required to achieve a given deflection decreases as a cubic function of the bending region’s length, so a long neck dramatically amplifies mobility. Conversely, the short-necked Trimerorhachis, with only three neck vertebrae and a neck less than 3 centimetres long, managed a mere 1 degree of lateral flexion. Geometry mattered too: taller, narrower vertebral columns were more restrictive, and the rectangular profile of Trimerorhachis limited bending even in longer column sections.

The most consequential finding is what the model did not show. Neck mobility did not increase in conjunction with the head–shoulder separation that occurred between the origin of tristichopterids, represented by Eusthenopteron, and more crownward stem tetrapods. The flexion capacities of Eusthenopteron and Tiktaalik actually exceed those of Acanthostega and Greererpeton by two- to threefold, despite comparable neck lengths. This means the separation event, documented in the common ancestors shared by Tiktaalik and Acanthostega but not with Eusthenopteron, had no detectable effect on how far the head could move. The tetrapod neck, the authors argue, appears to have evolved as a by-product of head–shoulder separation rather than as an adaptation for mobility.

If neck mobility was not the functional driver of the separation, what was? The researchers point instead to forelimb-driven locomotion. Across the tetrapod stem, the pectoral fin and girdle underwent substantial anatomical changes, including rearrangement of the long bones and loss of lepidotrichia. Eusthenopteron already possessed a stress-dissipating trabecular architecture in its humerus capable of supporting weight bearing, and derived stem tetrapods such as Ichthyostega are hypothesized to have used pectoral-powered locomotion in contact with the substrate, similar to terrestrial locomotion observed in several living fishes. The shoulder girdle’s primary function, on this view, shifted from connecting head to trunk to supporting forelimb function. A stiff neck, far from being a liability, may have been advantageous—increasing energetic efficiency during swimming and providing passive resistance to gravity on land. Substantial, independent head motion, as seen in Whatcheeria and later crown tetrapods, evolved secondarily through longer necks and mobile intervertebral joints. The findings also cast doubt on hypothesized terrestrial feeding modes for early tetrapods, since limited head mobility would preclude lateral snapping while the forelimb was planted, and instead align with aquatic feeding hypotheses in which trunk flexion contributed to overall motion.

Subject of Research: Biomechanical modelling of neck mobility in early tetrapods using lake sturgeon as an extant analogue

Article Title: Early tetrapod neck mobility modelled using an extant analogue

Article References: Korneisel, D. E., Donatelli, C. M., Han, L., Stewart, T. A., Traynor, A. L., Otoo, B. K. A., Martinez, M., Miyashita, T., Standen, E. M., & Maddin, H. C. (2026). Early tetrapod neck mobility modelled using an extant analogue. Nature. https://doi.org/10.1038/s41586-026-11158-3

Image Credits: AI Generated

DOI: 10.1038/s41586-026-11158-3

Keywords: tetrapod evolution, neck mobility, sturgeon, notochord, palaeontology, biomechanics, Tiktaalik, Acanthostega, Whatcheeria, vertebral column, Devonian, material testing

The stakes of this question are enormous. Insects are the most species-rich group of animals on Earth, with more than one million formally described living species, and the origin of powered flight in insects stands among the most transformative events in the history of terrestrial life. Wings opened up the air as a habitat, transformed pollination and predation, and set the stage for the staggering diversity that followed. Yet the relationships among the three major pterygote lineages, Ephemeroptera (mayflies), Odonata (dragonflies and damselflies), and Neoptera (insects capable of folding their wings back over their bodies), remained stubbornly unresolved, with competing hypotheses each backed by different bodies of evidence.

Three rival scenarios defined the debate. The Palaeoptera hypothesis holds that mayflies and odonates share a common ancestor, forming a clade called Palaeoptera that is the sister group of all other winged insects. The Chiastomyaria hypothesis instead pairs dragonflies with a grouping of mayflies and neopterans. The Metapterygota hypothesis takes the opposite arrangement, pairing mayflies with neopterans and leaving dragonflies on the earliest branch. Because these topologies imply very different histories for how wings were structured, how they moved, and how insect flight first evolved, resolving them has been a central challenge in reconstructing the insect tree of life.

The new study attacked the problem with an unusually comprehensive dataset. The researchers sequenced 16 new genomes from Chinese mayflies, a lineage that had been chronically undersampled in previous phylogenomic work, and integrated genomic and transcriptomic data from more than 100 insect species overall. This effort substantially closed the gaps in both taxon sampling and gene sampling that had plagued earlier analyses. The team then constructed two large amino-acid supermatrices built from universal single-copy orthologous nuclear genes, ensuring that the comparisons were based on genes present in exactly one copy across the sampled species and therefore less likely to mislead through ancient duplications.

What distinguishes the study is the systematic rigor applied to the analysis. Rather than relying on a single method, the researchers examined phylogenetic signals using both concatenation approaches, which pool all genes into one matrix, and multispecies coalescent methods, which model how individual gene trees relate to the underlying species tree. They deployed multiple evolutionary models, performed formal topological tests, dissected signals at the level of individual sites in the alignments, and ran simulation analyses to check whether their methods could recover the true tree under known sources of error. Across all of these diverse frameworks, the results consistently supported the monophyly of Palaeoptera: mayflies and odonates are sister groups, together forming the sister clade of Neoptera.

That consistency matters because the study also explains why the problem had resisted resolution for so long. During the rapid early radiation of winged insects, the researchers found that a combination of incomplete lineage sorting, in which ancestral genetic polymorphisms are randomly partitioned among descendant lineages, and gene tree estimation error affected approximately 40 percent of the gene trees in their dataset. This produced widespread topological discordance between individual gene trees and the true species tree. Different analytical frameworks handled this noise differently, which is precisely why earlier phylogenomic studies reached competing conclusions. By quantifying the scale of the problem and applying methods robust to it, the team was able to cut through the conflicting signals.

The resolution of the tree carries a profound implication for how we understand the origin of insect flight. Because mayflies and dragonflies, which cannot fold their wings flat over their bodies, form a group that is sister to the foldable-winged Neoptera, the non-foldable wings of Palaeoptera and the foldable wings of Neoptera are both novel traits that were independently acquired from an ancestral winged insect. In other words, the wing-folding mechanism of neopterans was not the retention of a primitive condition lost by mayflies and dragonflies; it was a later innovation. The ancestral winged insect already had wings, but neither the rigid flight apparatus of modern palaeopterans nor the folding hinge of modern neopterans.

To place these branching events in time, the researchers used molecular-clock analyses calibrated with 13 carefully selected fossil reference points. The results indicate that crown-group Pterygota, the lineage containing all living winged insects and their most recent common ancestor, originated in the Early Devonian, while crown-group Palaeoptera arose later, in the Late Devonian. Crucially, the analysis supports the conclusion that insect wings evolved only once. The subsequent history of the group was one of divergence and independent refinement of two very different flight architectures rather than repeated origins of flight itself.

The functional consequences of those two architectures shaped everything that followed. In neopterans, the wing-folding mechanism is enabled by rotation of the independent third axillary sclerite, a small skeletal element at the wing base that allows the hindwings to be tucked back over the abdomen. This seemingly modest anatomical feature provided the morphological and ecological foundations for the explosive radiation of Neoptera after the Carboniferous, since insects that could fold their wings could crawl through vegetation, burrow, and exploit microhabitats closed to insects with permanently outstretched wings. Mayflies and dragonflies, by contrast, evolved highly specialized rigid wing-base complexes adapted for gliding or high-speed predatory flight, trading the flexibility of folding for performance in the air.

The reconstructed evolutionary scenario shows that after the initial divergence of winged insects, Palaeoptera and Neoptera rapidly split and evolved their distinct wing structures in parallel: Neoptera developing its unique wing-folding apparatus, and Palaeoptera developing rigid wing bases for high-performance direct flight. Together, these innovations shaped the flight biomechanics and the species diversity of winged insects observed in nature today. The study was funded by the National Key R&D Program of China, the National Natural Science Foundation of China, and the China Postdoctoral Science Foundation. By uniting dense genome sampling, rigorous phylogenetic testing, and fossil-calibrated dating, the work demonstrates how a question posed in the nineteenth century can finally be answered with the tools of the twenty-first, and it offers a template for resolving other deep branches in the tree of life where rapid ancient radiations have scattered contradictory signals across the genomes of living species.

Subject of Research: Phylogenomic resolution of early winged insect evolution and the Palaeoptera Problem

Article Title: Genomic and fossil evidence sheds new light on the early evolution of winged insects

Article References: Genomic and fossil evidence sheds new light on the early evolution of winged insects. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: phylogenomics, Palaeoptera, insect evolution, mayflies, dragonflies, Neoptera, insect wings, molecular clock, Devonian, incomplete lineage sorting, fossils, PNAS

Brunia, sometimes known by its older name Brunovistulia, forms the easternmost corner of the Bohemian Massif, the great block of old rocks that anchors Central Europe. Its foundation is a late Neoproterozoic volcanic arc complex, built by magmas rising above a subduction zone roughly 630 to 580 million years ago, and capped by Ediacaran and early Cambrian sediments. During the Carboniferous collision that built the Variscan Mountains, the western edge of Brunia was thrust eastward over its own relatively undeformed interior, creating the Moravian and Silesian nappes. But where Brunia actually sat on the Paleozoic globe — attached to the microcontinent Avalonia, welded to Baltica, or bound to its Bohemian neighbors — has remained fiercely contested.

The new study attacked the problem with detrital zircon geochronology, a technique that exploits zircon’s extraordinary resistance to erosion and its ability to trap uranium and hafnium isotopes at crystallization. The team analyzed 19 samples from Devonian clastic strata across Brunia’s basin systems, from shallow marine quartzites in the north to deep-water turbidites near Brno. A total of 2,407 uranium-lead isotopic analyses yielded 2,184 concordant ages, supplemented by 241 hafnium isotope measurements that fingerprint the mantle or crustal origin of each zircon’s parent magma. The result was not one story but two, sharply and unexpectedly different.

Fourteen of the samples, labeled Type-1, produced nearly unimodal age spectra dominated by zircons between roughly 590 and 620 million years old, with fewer than 3 percent of grains older than 720 million years. Their hafnium signatures were strikingly juvenile, with epsilon-Hf values mostly between +4 and +10, indicating derivation from primitive magmas rather than recycled old crust. This signature points squarely at the Slavkov Domain, the juvenile arc granitoids preserved within Brunia’s own basement. In other words, most Devonian rivers draining Brunia were simply recycling their own Ediacaran arc, grain by grain, with little input from anywhere else.

That local story, however, carries a global message. When the team compared Brunia’s zircon spectra with datasets from around the North Atlantic realm, the closest match was not to neighboring terranes of the Bohemian Massif but to the late Neoproterozoic strata of West Avalonia on the Avalon Peninsula of Newfoundland. There, more than 90 percent of zircons fall in the same 900 to 485 million year window, and the hafnium values are similarly positive. The implication is that Brunia and West Avalonia shared a single Neoproterozoic volcanic arc system near the Gondwanan margin before drifting apart — a kinship that, according to faunal and paleomagnetic evidence, had already been severed by the early Cambrian, when Brunia appears to have docked against Baltica.

Just as telling is what the data exclude. Ediacaran and Cambrian strata elsewhere in the Bohemian Massif — in Teplá-Barrandia and Saxo-Thuringia — show far broader age spectra and much wider, often negative, hafnium ranges, indicating additional crustal sources that Brunia lacks. The study therefore argues against models that weld Brunia, Teplá-Barrandia, and Saxo-Thuringia into one continuous crustal domain, suggesting instead that Brunia occupied an oceanward, fore-arc position relative to its cratonward Bohemian neighbors. Nor do the data support the idea that Brunia was the main supplier of the late Neoproterozoic zircons found across Baltica’s southwestern margin, whose sources were more diverse than Brunia alone could provide.

The second provenance signature, Type-2, came from five samples confined to the Vrbno Facies Domain in northern Brunia, and it is a different world entirely. Here the spectra are multimodal, with 89 percent of concordant analyses falling between 2,100 and 900 million years ago, prominent peaks near 1,670 million years, abundant Stenian to early Tonian grains, a scattering of Neoarchean zircons, and — crucially — a modest but decisive population of Late Ordovician to Silurian grains between 458 and 433 million years old. Statistical comparison using multi-dimensional scaling confirmed that this signature matches nothing within Brunia’s own basement. The zircons had to come from somewhere else entirely.

The answer, the authors conclude, is the Caledonian Mountains of Fennoscandia. Type-2 spectra closely resemble those of Late Ordovician and Silurian sandstones of the Oslo Rift and match Lower Devonian strata across an astonishing sweep of Laurussia: the Harz Mountains and Rhenish Massif of Germany, the Mid-German Crystalline Rise, the Baltic Basin of Estonia, the Anglo-Welsh Basin, North Dobrogea in Romania, and even the Istanbul Zone of northwestern Turkey. Similar signatures extend to the Orcadian Basin of Scotland, East Greenland, Svalbard, Novaya Zemlya, and the Acadian foreland basin of North America. Together they trace a vast sedimentary fan — a network of rivers, deltas, and seas dispersing Caledonian detritus across half a hemisphere during the late Silurian and Early Devonian, an Old Red Sandstone continent in full spate.

For Brunia, the presence of this Caledonian fingerprint in Devonian strata is direct proof that by Early Devonian time the terrane lay within reach of rivers draining the Scandinavian Caledonides — firm evidence of its connection to Baltica. Equally significant is where the signature stops. The Type-2 spectra are essentially absent from the internal domains of the European Variscides, and Devonian strata in Saxo-Thuringia instead carry Stenian zircons with the wide, negative hafnium ranges typical of Gondwanan sources. The lack of mixing between these two provenance signals implies that a barrier — most plausibly the still-open Rheic Ocean, or some formidable orographic divide — separated Brunia from the internal Bohemian Massif throughout the Devonian.

That conclusion places the Rheic suture, the scar of the vanished ocean, somewhere inside the Bohemian Massif itself rather than along its traditional boundary at the Moldanubian Thrust Zone. Recent discoveries of Mesoproterozoic crustal material deep within Moldanubia only deepen the mystery. Resolving it, the authors argue, will require targeted provenance studies of the region’s high-grade metamorphic rocks — a reminder that some of Earth’s most consequential geography is still hidden in the oldest grains beneath our feet.

Subject of Research: Detrital zircon provenance analysis of Devonian sedimentary strata of the Brunia terrane in the Bohemian Massif

Article Title: A vast Caledonian fan and an Ediacaran arc: the contrasting provenance of Devonian clastics of Brunia (Bohemian Massif)

Article References: Collett, S., Soejono, I., Kumpan, T., Hanžl, P., Míková, J., Novotná, N., & Sláma, J. (2026). A vast Caledonian fan and an Ediacaran arc: the contrasting provenance of Devonian clastics of Brunia (Bohemian Massif). Solid Earth, 17(6), 867-893. https://doi.org/10.5194/se-17-867-2026

Image Credits: AI Generated

DOI: 10.5194/se-17-867-2026

Keywords: Brunia, Bohemian Massif, detrital zircon, U-Pb geochronology, Lu-Hf isotopes, Devonian, Caledonides, Avalonia, Baltica, Rheic Ocean, Variscan orogeny, provenance

The placoderms in question lived around 385 million years ago during the Devonian Period, often called the Age of Fishes, in the rich marine ecosystems of the famous Gogo Formation in Western Australia. This world-renowned fossil site has been the focus of decades of research, including long-running collaborations with the local Gooniyandi and Gogo community, and has yielded some of the most exquisitely preserved three-dimensional fish fossils ever discovered. It was here that these armoured predators hunted other armoured creatures on an exotic ancient reef, and it is here that the fossil evidence for their feeding strategies has been locked away in stone, waiting for modern technology to unlock it.

Dr Alice Clement, an ARC Future Fellow at the Flinders Palaeontology Lab and a co-author of the study, explains that placoderms present an extraordinary natural experiment in the early evolution of biting. Placoderms experimented with an extraordinary range of jaw shapes and biting parts during the early evolution of vertebrates, she notes, providing a rare opportunity to understand how some of the first jaws became specialised for different diets. Unlike most animals alive today, including humans, placoderms did not possess a single lower jaw bone. Instead, their jaws were built from paired bony plates supported by cartilage, with biting surfaces that ranged from broad, flat crushing plates to sharp slicing edges armed with tooth-like structures. This anatomical diversity makes them ideal subjects for investigating how jaws first became adapted to different kinds of food.

To probe that diversity, the research team employed a technique borrowed from engineering known as finite element analysis. First author Dr Rex Mitchell, of the College of Science and Engineering at Flinders University, together with colleagues, created digital three-dimensional models of the fossil jaw bones and then performed computer-based bite simulations on them. These simulations measure how well each jaw structure could withstand and support the forces generated during biting, effectively stress-testing extinct animals in silico. The team then compared the mechanical performance of each jaw with the anatomical complexity of its biting surface, looking for patterns that might connect jaw shape to diet and feeding behaviour across the eight species they examined.

Conventional wisdom in biomechanics holds that animals feeding on hard foods, such as shells and bone, generally evolve stronger jaws with broader, flatter crushing surfaces, much like the nutcracker jaws of modern hyenas or the durophagous dentitions of many rays and wrasses. That is not exactly what the analysis revealed. Rather than finding a simple, predictable relationship between jaw strength and surface shape, the researchers discovered something unexpected: both the largest and the smallest placoderms in the study possessed the strongest jaws for handling hard bites, despite using completely different biting tools. The smallest species had broad, almost featureless crushing plates, while the largest species carried highly complex, elevated dental surfaces that bore little resemblance to their diminutive relatives.

It was an interesting surprise, says PhD student and co-author Austin Fitzpatrick. Both the smallest and largest animals had evolved strong jaws, he explains, but they had solved the problem of processing harder foods in completely different ways. The key to this paradox, the researchers suggest, lies in the relationship between predator and prey body size when the prey in question is wrapped in tough exterior armour. A small placoderm confronting a small armoured prey item did not need to break it apart at all. The prey could simply be engulfed whole and then pulverised between broad, flat biting plates, much as some modern fish swallow and crush small shelled invertebrates. Strength was essential, but anatomical complexity was not.

Larger prey presented an entirely different challenge. An armoured animal too big to fit inside a predator’s mouth first had to be broken into manageable pieces before it could be eaten. That requirement demanded more elaborate dental architecture, capable of first piercing through shell or armour before crushing the remains. The largest species in the study possessed teeth arranged along a raised bony crest, forming a structure that the researchers describe as strikingly similar to the heads of medieval armour-piercing weapons such as war hammers and poleaxes. This fearsome configuration suggests the fish used its jaws to puncture the protective coverings of its prey before breaking them apart, functioning less like a nutcracker and more like a can opener followed by a hammer.

The broader significance of the finding is that hard-object feeding among Earth’s earliest jawed vertebrates was not achieved through a single evolutionary solution. Evolution, in other words, produced a diversity of jaw designs that allowed different placoderm species to exploit different prey within the same ancient reef ecosystem, a pattern ecologists call niche separation. Two species could both be powerful biters specialised for hard-shelled food, yet occupy genuinely different ecological roles depending on what they could fit in their mouths and how they had to dismantle it. This paints a picture of the Devonian reef as a complex, ecologically structured environment in which early vertebrates were already carving out specialised feeding niches hundreds of millions of years before the first tetrapods crawled onto land.

The study also reinforces the central place of placoderms in the story of human evolution. Flinders Emeritus Professor John Long, a co-author who has worked at the Western Australian fossil site for 40 years and found some of the specimens used in this study, emphasises that since 2013 placoderms have been directly linked to our own lineage as the starting point of the line leading from fishes to humans. Understanding placoderms, he argues, is now vital to revealing the origins of the human body plan. Their jaws, in particular, represent the evolutionary foundation upon which all later vertebrate mouths, from shark snouts to human faces, were ultimately built, making every new insight into how these structures functioned a contribution to a deeply personal chapter of natural history.

Technically, the study demonstrates the growing power of combining finite element analysis with comparative three-dimensional morphology to answer ecological questions that fossils alone cannot resolve. By measuring jaw strength numerically and then mapping it against surface complexity, the team could infer not only what these extinct fish ate but also how large their prey must have been relative to their own bodies, turning bite mechanics into a proxy for ancient food webs. The work, supported by the Australian Research Council through Discovery Projects funding, contributes to a growing picture of niche separation and ecological specialisation in the ancient Devonian reef. It shows that within a few tens of millions of years of jaws first appearing, vertebrates had already diversified into an impressive array of feeding specialists, from whole-swallowing crushers to armour-piercing giants, foreshadowing the extraordinary ecological breadth of jawed vertebrates that continues to this day.

Subject of Research: Feeding mechanics and jaw evolution in Devonian placoderms from the Gogo Formation, Western Australia

Article Title: Jaws tell tales: How ancient armoured fish munched prey whole

Article References: Jaws tell tales: How ancient armoured fish munched prey whole. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: placoderms, Devonian, Gogo Formation, jaw evolution, finite element analysis, hard-object feeding, palaeontology, Flinders University, vertebrate evolution, fossil fish, predator-prey relationships, ancient reefs