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 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