Healed predation scar on a Cambrian apex predator
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eLife Assessment
In this useful study, Du and colleagues report a fossil specimen of a swimming flap probably belonging to the radiodont Amplectobelua symbrachiata from a new locality of the early Cambrian Chengjiang Biota. The authors interpret a W-shaped notch as the first evidence of healed injuries on an apex predator of the Cambrian. With this reasonable and solid evidence, the manuscript has potential significance for understanding ecological interactions among high trophic levels in the Cambrian.
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Abstract
Predation is considered a key driver of the rapid diversification of animals during the Cambrian explosion. While the fossil record documents a plethora of evidence of successful and failed predation on biomineralized invertebrates at low trophic levels, no previous evidence of predation on larger, often soft-bodied, animals at higher trophic levels has been reported. This means that the modeled links between higher trophic levels in Cambrian food webs lack supporting fossil evidence, hindering understanding of the complexity of Cambrian trophic relationships. Here, we report a healed injury on the swimming flap of the radiodont apex predator Amplectobelua symbrachiata— one of the largest animals in the Cambrian oceans. The diagnostic W-shape with a healed margin supports interpretation of this wound as predatory in origin, with likely attackers including larger contemporaneous radiodonts – possibly members of the same species -- or the giant lobopodian Omnidens. Evidence that apex predators were attacked provides critical empirical data informing the complexity of Cambrian food webs. This finding provides empirical support for the existence of high-level feeding loops, analogous to those in modern marine ecosystems, documenting the rapid increase in trophic complexity during the latter stages of the Ediacaran-Cambrian Transition.
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eLife Assessment
In this useful study, Du and colleagues report a fossil specimen of a swimming flap probably belonging to the radiodont Amplectobelua symbrachiata from a new locality of the early Cambrian Chengjiang Biota. The authors interpret a W-shaped notch as the first evidence of healed injuries on an apex predator of the Cambrian. With this reasonable and solid evidence, the manuscript has potential significance for understanding ecological interactions among high trophic levels in the Cambrian.
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Reviewer #1 (Public review):
Summary:
Du and colleagues carefully report a fossil specimen of a swimming flap belonging to the radiodont Amplectobelua symbrachiata from a new locality of the early Cambrian Chengjiang Biota. The margin of this isolated flap preserves a W-shaped notch with a thickened dark band along the notch edge. The authors interpret this structure as a healed predation scar formed during the life of the radiodont and further discuss potential attackers and the complexity of the Cambrian high-trophic-level food web. The preservation of the soft-bodied fossil specimen is exquisite, and the manuscript is high quality and novel.
Strengths:
The topic is novel and interesting, and the exquisite specimen itself has high potential paleoecological value. It is particularly commendable that the authors attempt to discuss the …
Reviewer #1 (Public review):
Summary:
Du and colleagues carefully report a fossil specimen of a swimming flap belonging to the radiodont Amplectobelua symbrachiata from a new locality of the early Cambrian Chengjiang Biota. The margin of this isolated flap preserves a W-shaped notch with a thickened dark band along the notch edge. The authors interpret this structure as a healed predation scar formed during the life of the radiodont and further discuss potential attackers and the complexity of the Cambrian high-trophic-level food web. The preservation of the soft-bodied fossil specimen is exquisite, and the manuscript is high quality and novel.
Strengths:
The topic is novel and interesting, and the exquisite specimen itself has high potential paleoecological value. It is particularly commendable that the authors attempt to discuss the origin of this anomalous structure by integrating morphology, Micro-XRF, analogy with wound healing in extant arthropods, and functional morphological estimation. The research approach is relatively comprehensive. This study has considerable scientific significance for exploring predator-prey relationships at high trophic levels in the Cambrian marine ecosystem. In addition, an important highlight of the manuscript is that it clarifies that the distal dorsal spines and terminal spines of the frontal appendages of radiodonts are paired, rather than uniserial as previously thought, correcting some previous misunderstandings.
Weaknesses:
The paper does have some shortcomings. My main concerns are as follows:
(1) In the inferential chain from the "W-shaped anomaly" to "antemortem injury", then to "healing", then to "predation", and finally to "high-trophic-level feeding loops", the strength of evidence at several links is not entirely consistent. Some sentences present interpretive conclusions as directly proven facts.
(2) One of the most critical pieces of evidence is the W-shaped notch and the dark band along its edge. The authors compare the dark edge to scarification structures in trilobites and to melanisation during wound healing in extant arthropods, and on this basis further interpret it as a healed predatory injury. However, the current evidence first supports that the structure may represent an antemortem trauma and subsequent repair, but is not sufficient to uniquely prove that it was caused by predation. Even if the W-shaped notch is indeed an antemortem injury, it could still be related to other mechanical injuries, non-predatory attacks between individuals (e.g., resulting from intra- or interspecies competition), molting-related tears, or other traumatic processes. It is generally difficult to correlate one type of wound with one potential predator. The W-shaped wound could also have resulted from multiple injuries during a single attack. I suggest that the authors treat "whether repair occurred" and "whether caused by predation" as two independent questions and argue them separately, and avoid treating the W-shaped outline itself as a diagnostic feature of predation.
(3) The authors provide a discussion of alternative explanations such as decay, burial, molting, parasite-induced pathological changes, developmental malformations, and competitive behavior, which is a strength of this paper. However, some of the current arguments mainly rely on "lack of evidence supporting these alternative explanations" to support the predation interpretation, which is still insufficient.
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Reviewer #2 (Public review):
Summary:
This article reports what appears to be the first evidence of healed injuries on an apex predator of the Cambrian: a radiodont flap, probably belonging to Amplectobelua symbrachiata. Because the injuries show signs of healing, the animal survived the attack, which provides direct evidence of predatory interactions among the apex predators of the Cambrian and sheds new light on the structure of food webs at that time.
Strengths:
The manuscript is short but well written, and the evidence for healing is clearly presented. I find this study genuinely interesting and a valuable contribution to our understanding of Cambrian ecosystems. The figures are of high quality and help readers understand both the results and the interpretations proposed by the authors.
Weaknesses:
My main criticism concerns the …
Reviewer #2 (Public review):
Summary:
This article reports what appears to be the first evidence of healed injuries on an apex predator of the Cambrian: a radiodont flap, probably belonging to Amplectobelua symbrachiata. Because the injuries show signs of healing, the animal survived the attack, which provides direct evidence of predatory interactions among the apex predators of the Cambrian and sheds new light on the structure of food webs at that time.
Strengths:
The manuscript is short but well written, and the evidence for healing is clearly presented. I find this study genuinely interesting and a valuable contribution to our understanding of Cambrian ecosystems. The figures are of high quality and help readers understand both the results and the interpretations proposed by the authors.
Weaknesses:
My main criticism concerns the interpretation of the shape of the injuries and, therefore, how the predation would have occurred. The injuries are presented as W-shaped, which is true for only part of them. This contrasts with the drawing, which shows a large W-shaped injury that fits the oral cone drawing perfectly. I think it is too simplified compared to the real shape of the injury. To me, it looks more like a large V-shape with two irregularities. In my opinion, the large V-shape could correspond to a bite from the oral cone, but shaped by one plate only, while the two irregularities, which led the authors to call it W-shaped, could have been shaped by the frontal appendages. It could therefore be proof of the function of the appendages: grasping prey to bring it to the mouth. It also seems that the oral cone drawing used as a model is not identified. Do we have an Amplectobelua oral cone, or does it suggest Ramskoeldia? This needs further clarification. A new paper on radiodont oral cones, which figures most of them, has just come out (Potin et al. 2026, Swiss Journal of Palaeontology).
Omnidens is also mentioned as a potential predator; however, this is not supported by any drawing, which would be good to have, as it is mentioned in the abstract.
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Healed predation scar on a Cambrian apex predator https://www.biorxiv.org/content/10.64898/2026.08.01.742255v1
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Healed predation scar on a Cambrian apex predator https://www.biorxiv.org/content/10.64898/2026.08.01.742255v1
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