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Four camera-type eyes in the earliest vertebrates from the Cambrian Period

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Abstract

Vertebrate vision is mainly accommodated by a pair of lateral image-forming camera-type eyes and is supplemented in non-mammalian vertebrates by a dorsal pineal complex (pineal and parapineal organs) functioning as photoreceptive and/or endocrine organs1. The pineal complex shares a common genetic and embryological basis with the lateral eyes, both derived from evaginations during the development of diencephalon2. Despite being widely heralded as the ‘third eye’ in crown vertebrates3, the nature of the pineal complex and its presumed visual capability in early vertebrates2 remain unknown. Here we describe two pigmented features situated between the lateral eyes in two species of myllokunmingids, the earliest known fossil vertebrates (approximately 518 million years ago), and interpret these as pineal/parapineal organs. In both myllokunmingid species, the pineal complex contains abundant melanin-containing melanosomes identical to those in the retinal pigment epithelium in the lateral eyes, together with a distinctive, regularly ovoid structure interpreted as a lens. Our results indicate that the lateral eyes and pineal complex in myllokunmingids probably functioned as camera-type eyes capable of image formation. Thus, we propose that the four camera-type eyes represent an ancestral vertebrate character, corroborating hypotheses about the deep homology between the eyes and pineal complex.

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Fig. 1: General morphology of the lateral eyes and pineal complex with their preserved melanosomes in two species of Myllokunmingidae from the Chengjiang biota.
Fig. 2: Negative ion ToF-SIMS spectra of melanosomes in the eyes of Chengjiang myllokunmingids.
Fig. 3: Preserved lens in the eyes and pineal complex of Cambrian vertebrates.
Fig. 4: Evolutionary scheme of the visual system in early vertebrates.

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All supporting data of this study are available at Figshare (https://doi.org/10.6084/m9.figshare.29589761).

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Acknowledgements

We thank the students from the research group on problematic fossils and the early animal radiation event at Yunnan University for their assistance with fieldwork. We are grateful to M. Brazaeu for discussions on the presence of pineal eyes in early vertebrates; T. Zhao for comments on an early version of the paper; J.-B. Caron for providing images of M. walcotti; and T. Clements for providing images of Elonichthys peltigerus, Platysomus circularis and Bandringa rayi. We also thank J. Xie, D. Gao and J. Yang (Electron Microscopy Center of Yunnan University) for assistance with FIB and TEM analyses, as well as L. Sun (Electron Microscopy Center at Shanghai Jiaotong University) for ToF-SIMS analysis. This study was funded by the Yunnan Science & Technology Champion Project (202305AB350006) and the National Natural Science Foundation of China (42072019). P.C. acknowledges support from the Yunling Scholarship of the Yunnan Revitalization Talent Support Program.

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Author notes

  1. These authors contributed equally: Xiangtong Lei, Sihang Zhang

Authors and Affiliations

  1. Center for Vertebrate Evolutionary Biology, School of Life Science, Yunnan University, Kunming, China

    Xiangtong Lei  (雷向通) & Xing Xu  (徐星)

  2. State Key Laboratory for Vegetation Structure, Functions and Construction (VegLab), Institute of Palaeontology, Yunnan University, Kunming, China

    Xiangtong Lei  (雷向通), Sihang Zhang  (张思航), Peiyun Cong  (丛培允) & Fan Wei  (魏凡)

  3. Oxford University Museum of Natural History, University of Oxford, Oxford, UK

    Peiyun Cong  (丛培允)

  4. Palaeobiology Research Group, School of Earth Sciences, University of Bristol, Bristol, UK

    Jakob Vinther

  5. School of Biological Sciences, University of Bristol, Bristol, UK

    Jakob Vinther

  6. Centre for Palaeobiology and Biosphere Evolution, School of Geography, Geology and the Environment, University of Leicester, Leicester, UK

    Sarah Gabbott

  7. Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China

    Xing Xu  (徐星)

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  1. Xiangtong Lei  (雷向通)
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Contributions

P.C., S.G. and J.V. conceived the project. P.C., X.L., S.Z. and F.W. collected the specimens. X.L. and S.Z. collected and analysed the data and, together with the other authors, wrote the first draft of the paper. X.L. and S.Z. made the figures. P.C. and X.X. secured funding. P.C., J.V., S.G. and X.X. supervised the project and edited the paper.

Corresponding author

Correspondence to Peiyun Cong  (丛培允).

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Extended data figures and tables

Extended Data Fig. 1 Preservation of eyes and lens in selected fossil vertebrates.

a-b, Haikouichthys ercaicunensis (YNGIP-90285) showing lateral eyes (grey) and pineal eyes (green) with lens (blue). c, carbon element map of H. ercaicunensis (YNGIP-90285) head. d, H. ercaicunensis (YNGIP-90284), white arrows showing lens. e, H. ercaicunensis (YNGIP-90296). f, carbon element map of H. ercaicunensis (YNGIP-90296), yellow arrows indicating left pineal eye. g, (YNGIP-90283), eyes of H. ercaicunensis showing lens (white arrows). h, eyes of H. ercaicunensis showing lens (white arrows) (YNGIP-90289). i, carbon element map of the same region in h, note the absence of carbon in the lens (white arrows). j, m, lens in Elonichthys peltigerus (ROM56794). k, n, lens in Platysomus circularis (PF7333). l, o, lens in Bandringa rayi (ROM56789). (j–o) image courtesy of Thomas Clements. Scale bars, 200 μm (a–f); 50 μm (g–i); 5 mm (j–o). Panels j–o reproduced with permission from ref. 7, Springer Nature Limited.

Extended Data Fig. 2 Raman spectroscopic data across specimens supporting remains in the Chengjiang myllokunmingids eyes are organic material.

Note the consistency of Raman spectroscopic data across specimens, which are distinct from the negative control of the Chengjiang sediment. D and G, feature bands of organic materials.

Extended Data Fig. 3

X-ray photoelectron spectroscopy (XPS) analysis of carbonaceous remains in the eyes of the Chengjiang myllokunmingids (YNGIP 90291).

Extended Data Fig. 4 The frequency distribution and Gaussian fitting of the length-to-width ratio of the melanosomes in the eyes of the Chengjiang vertebrates.

a, Haikouichthys ercaicunensis (n = 549). b, myllokunmingid sp. (n = 500). n refers to the measured number of melanosome microbodies. xc: peak centre value; R2: regression coefficient.

Source Data

Extended Data Fig. 5 The frequency distribution and Gaussian fitting of the length-to-width ratio of the melanosomes in the lateral and pineal eyes of Haikouichthys ercaicunensis.

a, pineal eyes (n = 250). b, lateral eyes (n = 549). n refers to the measured number of melanosome microbodies. xc: peak centre value; R2: regression coefficient.

Source Data

Extended Data Fig. 6 SEM, FIB and TEM images of the melanosome in the eyes of Haikouichthys ercaicunensis.

a-b, Backscattered electron image (SEM) of H. ercaicunensis head. c-d, Secondary electron image (SEM) of the melanosome in the eyes (arrowed in a) of H. ercaicunensis. e, f, FIB slicing of the eye (arrowed in a) of H. ercaicunensis. g, i, TEM images of single melanosomes microbody, with enlarged details in i (boxed in g). h, Carbon (C, red), silicon (Si, blue), and iron (Fe, green) elemental map of a single melanosome as shown in g. Scale bars, 500 μm (a); 20 μm (b); 2 μm (c-f); 100 nm (g, h); 20 nm (i).

Extended Data Fig. 7 Detailed PCA result of negative ToF–SIMS spectra.

a, the PCA result of 54 negative secondary ion peaks obtained from the following samples: fresh melanin, artificially matured melanin (aged for 24 h at 200 °C/250 bar and 250 °C/250 bar), fossil melanin, various melanin-negative controls, and specimens of Chengjiang myllokunmingids. b, Comparison of ToF-SIMS full spectra between Haikouichthys eyes (top) with a negative control of the host sediment (bottom) from the Chengjiang biota. c, loadings for principal component analysis (panel a and Fig. 2a), showing the contribution of specific ion fragments to the positioning of specimens along the x-axis (PC1) and y-axis (PC2), respectively. d, the list of details of the numbered samples in a.

Extended Data Fig. 8 Swarming behaviour of myllokunmingid sp.

a, YNGIP-90293, b, YNGIP-90292, with individuals occurring in dense aggregations. Scale bar, 2 cm (a), 1 cm (b).

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Lei, X., Zhang, S., Cong, P. et al. Four camera-type eyes in the earliest vertebrates from the Cambrian Period. Nature (2026). https://doi.org/10.1038/s41586-025-09966-0

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