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A Cambrian soft-bodied biota after the first Phanerozoic mass extinction


Abstract

Cambrian Burgess Shale-type (BST) fossil biotas document nearly complete snapshots of the oldest Phanerozoic marine ecosystems1,2,3,4. However, the rarity of deposits bearing high-diversity BST biotas5 has restricted our understanding of the evolutionary and ecological dynamics of the Cambrian explosion. Here we report the Huayuan biota—a lower Cambrian (Stage 4, approximately 512 million years ago) BST Lagerstätte from an outer shelf, deep-water setting of the Yangtze Block in Hunan, South China. The Huayuan biota yields remarkable taxonomic richness, comprising 153 animal species of 16 phylum-level clades dominated by arthropods, poriferans and cnidarians, among which 59% of species are new. The biota is comprised overwhelmingly of soft-bodied forms that include preserved cellular tissues. The complex ecosystem contained diverse radiodonts and pelagic tunicates, filling a gap of high-diversity BST biotas from the Cambrian Stage 4. Critically, multivariate ordination based on a global dataset of Cambrian BST biotas places the Huayuan biota within a main transition of marine animal ecosystems between Cambrian Age 3 and Age 4. Network analysis reveals close faunal connections between the Huayuan and Burgess Shale biotas, indicating transoceanic dispersal. Dated shortly after the Sinsk event6,7,8, the Huayuan biota illuminates differences in the impacts of this extinction in shallow- versus deep-water settings during the first Phanerozoic mass extinction and offers critical insights into the transformation of global ecosystems in the early Cambrian.

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Fig. 1: Geological settings of the Huayuan biota.
Fig. 2: Non-bilaterian metazoans, deuterostomes and problematic taxa from the Huayuan biota.
Fig. 3: Protostomes and additional problematic taxa from the Huayuan biota.
Fig. 4: Ecological and environmental contexts of the Huayuan biota.

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A juvenile-rich palaeocommunity of the lower Cambrian Chengjiang biota sheds light on palaeo-boom or palaeo-bust environments

Combining soft-bodied and three-dimensional fossils to reveal evolutionary modifications in early lingulellotretid brachiopods

Data availability

The occurrence data for diversity analysis were downloaded from the Paleobiology Database (https://paleobiodb.org/data1.2/occs/list.csv?interval=Ediacaran,Tremadocian&show=full,classext,genus,subgenus,acconly,ident,img,etbasis,strat,lith,env,timebins,timecompare,resgroup,ref,ent,entname,crmod) on 26 February 2025. The datasets used as the source data of analyses, as well as intermediate and final results from quantitative analyses, are deposited in the Science Data Bank at https://doi.org/10.57760/sciencedb.32659. The accession numbers of fossil specimens with prefix NIGP are provided in the text. All the other data analysed in this paper are available as part of the Article, Extended Data Figs. 1–10 or Supplementary Information.

Code availability

The R code involved in the quantitative analysis is deposited in the Science Data Bank76 at https://doi.org/10.57760/sciencedb.32659 and is licensed under GPL-3.

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Acknowledgements

We thank S. Long, X. Long and N. Xiong (Fenghuang County No.1 Ethnic Middle School) for assistance in fieldwork, Y. Fang and Q. Chen for facilitating the SEM–EDS analysis, S. Wu for facilitating the μCT scanning, Z. Kou for making polished slabs and thin sections and D. Yang for artistic reconstruction. We are grateful to the people’s governments of Shilan Town, Huayuan County, and Xiangxi Autonomous Prefecture for years of working permission and support during this study. This study was supported by the National Key Research and Development Program of China (2022YFF0800100, 2021YFA0718100), the National Natural Science Foundation of China (42330209, 42272019), the Natural Science Foundation of Jiangsu Province (BK20230110), the Youth Innovation Promotion Association of Chinese Academy of Sciences (2023322), the Excavation Project of the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NGBS202500) and the Guizhou Science and Technology Fund (Gui. Sci. Plat. ZSYS [2024]002).

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Authors

Contributions

H.Z. and Q.L. contributed equally to this study. M.Z. and F.Z. designed the project. M.Z., F.Z. and Z.Y. secured the funding and prompted completion of the project. F.Z. and H.Z. led the fossil collection in the field. Q.L. and S.H. scientifically discovered the fossil locality. Q.L. made the first fossil collection. H.Z., F.Z., Q.L., K.C., C.L., Y.L., Y.Z., D.W., Z.S. and C.H. carried out the fieldwork and measured the stratigraphic section. H.Z., Q.L., C.L., Z.S., K.C., Y.Z., Y.L., Y.H., L.M., H.S., B.P., G.L. and J.Z. identified the fossils. H.Z., Y.Z., Y.L., C.L., Z.S. and J.Z. sorted out the collection and counted the specimens. H.Z., D.W. and F.Z. compiled the ecological datasets for comparative studies and analysed the data. H.Z. photographed all the specimens, conducted the SEM–EDS and μCT analyses and prepared the figures. M.Z., G.L., X.Y., A.Y. and S.H. contributed critical geological and palaeoenvironmental insights. H.Z. wrote the paper with input from all the other authors. H.Z., F.Z., M.Z., Q.L., C.L., S.H., A.Y., G.L., X.Y., Z.Y., Y.L., Y.Z., D.W., Z.S., Y.H., H.S., B.P., K.C., L.M., J.Z. and C.H. participated in the interpretation of the material and in discussions.

Corresponding authors

Correspondence to
Fangchen Zhao or Maoyan Zhu.

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Extended data figures and tables

Extended Data Fig. 1 Sedimentary structures of the Balang Formation from the Renkupo section that yields the Huayuan biota.

a, One of the large carbonate nodules (length = ~60 cm, height = ~20 cm) within the black shale of Member 2 of the Balang Formation, 129 m below the base of fossil quarry. b, Small carbonate nodules (length = ~10–20 cm, height = ~1–3 cm) within the greyish shale at the basal part of Member 3 of the Balang Formation, 84 m below the base of fossil quarry. c, One of the largest slump lenses (length = ~130 cm, height = ~40 cm) showing nearly vertical bedding within the greenish shale of Member 3 of the Balang Formation, 51 m below the base of fossil quarry. d, A slump fold (thickness = ~40 cm), 40 m below the base of fossil quarry. e, Fossiliferous greyish shale yielding the Huayuan biota at the fossil quarry, showing thin siltstone laminations (thickness = ~1–3 mm) in light colour, 5.5–6 m above the base of fossil quarry. f, Greyish silty laminations with micro-scale ball-and-pillow load structures in light colour, ~40 m above the base of fossil quarry.

Extended Data Fig. 2 Polished slab and thin section from the fossiliferous greyish shale yielding the Huayuan biota at the Renkupo section.

a, Polished slab, showing millimeters-scale laminations. b, Thin section, as in the boxed area in panel a. c, Scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS) maps of the boxed area in panel b. In transmitted light image, micronodular carbonate cementation (bright in Ca and C maps) and quartz grains (bright in Si map) appear lighter, and pyrite lenses (bright in Fe map) appear black. Micronodular carbonate cementation and quartz grains are more concentrated within the lighter, coarser poorly sorted layers than the darker, homogeneous mudstone layers. Each test of SEM-EDS mapping was performed once.

Extended Data Fig. 3 Trilobite arthropods from the Huayuan biota.

ag, Oryctocephalids. a, Arthricocephalus chauveaui, NIGP 208805. b, Arthricocephalus xinzhaiheensis, NIGP 208806. c, Oryctocarella duyunensis, NIGP 208807. d, Duyunaspis duyunensis, NIGP 208808. e, Longaspis paiwuensis, NIGP 208809. f, Balangia balangensis, NIGP 208810. g, Changaspis elongata, NIGP 208811. h, i, Redlichiids. h, Redlichia (Pteroredlichia) chinensis, NIGP 208812. i, Breviredlichia sp. nov., NIGP 208813.

Extended Data Fig. 4 Additional non-bilaterian metazoans and deuterostomes from the Huayuan biota.

ac, Poriferans. a, Choia carteri, NIGP 208814. b, Hamptonia bowerbanki, NIGP 208815. c, Crumillospongia? sp. nov., NIGP 208816. dg, Cnidarians. d, New cnidarian A, showing gastric cavity (gs), NIGP 208817. e, Archotuba elongata, showing gastric cavity (gs), NIGP 208818. f, New cnidarian B, showing numerous tentacles (te), NIGP 208819. g, New cnidarian C, showing tentacles (te) with internal soft tissue (so) in dark colour, NIGP 208820. h, Vetulicolian, new banffozoan B, showing gut within tail (gt), NIGP 208821. i, New tunicate B, two individuals showing tunic (tu), gill bar (gb) in dark colour, and oral and atrial siphons (os, as), NIGP 208822. j, New echinoderm, showing numerous densely packed plates, attachment structure (as), and interpreted locations of ambulacra (am?), NIGP 208849.

Extended Data Fig. 5 Additional arthropods from the Huayuan biota.

ae, Radiodonts. a, New hurdiid A, complete individual showing serially arranged sets of setal structures (ss), NIGP 208823. b, New hurdiid B, frontal appendage, NIGP 208824. c, A complete oral cone, NIGP 208825. d, Caryosyntrips serratus, NIGP 208826. e, Guanshancaris kunmingensis, NIGP 208827. f, Megacheiran, new leanchoiliid A, showing delicate nervous system comprising ventral nerve cord (vn) and peripheral nervous tissue (pn), NIGP 208828. g, Isoxyid, Isoxys acutangulus, showing eye (ey), frontal appendage (fa), and gills (gl), NIGP 208829. h, i, Artiopods. h, Naraoia taijiangensis, showing soft tissues including gut diverticula (dv), NIGP 208830. i, Sidneyia cf. expanctans, showing exopodite gills (gl), NIGP 208831. j, Hymenocarine, new waptiid, showing gut (gt) and appendages (ap), NIGP 208832. k, Bradoriid, Comptaluta inflata, showing posterior appendages (ap), NIGP 208833.

Extended Data Fig. 6 Additional ecdysozoans and spiralians from the Huayuan biota.

ac, Priapulida. a, Palaeoscolecid, Tylotites sp. nov., showing triangular sclerites, NIGP 208834. b, New palaeoscolecid, showing everted pharynx (ph), introvert (in), scalids (sc) and gut (gt), NIGP 208835. c, New priapulid A, showing everted pharynx (ph), introvert (in), tail hook (hk) and gut (gt), NIGP 208836. df, Lobopodians. d, Collins’ monster-like new luolishaniid, showing gut (gt) and lobopods (lb), NIGP 208837. e, Hallucigenia sp. nov., showing gut and paired dorsal spines, NIGP 208838. f, New putative lobopodian B, showing numerous paired lobopod-like appendages (lb?), NIGP 208839. g, Problematic worm A, showing internal soft tissue and eliminated gut content (ec), NIGP 208840. h, Problematic worm B, showing internal soft tissue and a posterior projection (pp), NIGP 208841. i, Chaetognath, new chaetognath, close-up of jaw apparatus, NIGP 208842. j, New halwaxiid, showing anterior shell (as) and long curved sclerites, NIGP 208843. k, Problematic worm C, showing gut (gt) and other soft tissues, NIGP 208844. l, m, Brachiopods. l, Palaeobolus sp., showing pedicle (pd) and setae (st), NIGP 208845. m, Eohadrotreta duyunensis, showing pedicle (pd), NIGP 208846.

Extended Data Fig. 7 Fossil preservation of the Huayuan biota revealed by scanning electron microscopic energy dispersive spectroscopy (SEM-EDS) and X-ray microcomputed tomography (μCT).

a, Characteristic Burgess Shale-type preservation where soft tissue is preserved as carbonaceous film, which is covered by an additional coating of sparry calcite, as shown by the SEM-EDS maps of the problematic Herpetogaster collinsi, NIGP 208847. b, Iron-rich minerals capturing fossil morphology, as shown by the SEM-EDS maps and μCT maximum projection image of a possibly weathered specimen of the poriferan Crumillospongia? sp. nov., NIGP 208816. c, Original phosphatic preservation of biomineralized sclerite plates, with formation of pyrite grains on top of the sclerites, as shown by the SEM-EDS maps of the palaeoscolecid Wronascolex geyiensis, NIGP 208848. Each test of SEM-EDS mapping was performed once.

Extended Data Fig. 8 Taxonomic and ecological compositions of the Huayuan biota and its comparisons to other notable Cambrian Burgess Shale-type biotas.

a, Rarefaction curves of the Renkupo quarry and representative quarries of other Cambrian BST biotas. Dashed lines bordering shaded areas indicate confidential intervals of one standard error (mean ± s.e.m.). b, Taxonomic composition of the Huayuan biota. c, Bar plot showing the ranking of species abundance of the Huayuan biota. d, Bar plot showing the comparisons of taxonomic compositions between the Huayuan, Chengjiang, Qingjiang and Burgess Shale biotas. e, Bar plot showing the comparisons of ecological compositions between the Huayuan, Chengjiang, Qingjiang and Burgess Shale biotas. Abbreviations: DE, deposit feeder; ES, epifaunal sessile; EV, epifaunal vagrant; GR, grazer; HS, predator or scavenger; IS, infaunal sessile; IV, infaunal vagrant; NK, nektobenthic; OM, omnivore; PE, pelagic; SU, suspension feeder; UN, unknown.

Extended Data Fig. 9 Ecospace utilisationof the Huayuan biota and similarity matrices between Cambrian Burgess Shale-type biotas.

a, Ecospace occupation showing the tiering, feeding and motility of animals of the Huayuan biota. Colour gradients in the left and right ecospace cubes are based on species richness and proportion of individuals, respectively. b, Similarity matrices between representative Cambrian BST biotas with similarity value shown in heatmap colours, based on transformation of distance matrices in the non-metric multidimensional scaling analyses with singletons included, as shown in Extended Data Fig. 10c, e. Upper and lower triangles show results from using Jaccard and Ochiai index, respectively. The similarity values between the Huayuan (HY) and Burgess Shale (BS) biotas are annotated in black. See Extended Data Fig. 10a for abbreviations of biotas.

Extended Data Fig. 10 Spatiotemporal distribution of the Cambrian Burgess Shale-type biotas and comparisons of their taxonomic compositions.

a, Estimated geological time range of Burgess Shale-type (BST) biotas from Cambrian Epoch 2 to Miaolingian based on global biostratigraphic correlations (time ranges in Supplementary Table 2). b, Palaeogeographic reconstruction at 510 Ma based on PaleoAtlas and PaleoCoastlines data of the PALEOMAP Project56,65,66, showing the locations of BST biotas (palaeocoordinates in Supplementary Table 2). Note that the positions of plates only slightly changed from Cambrian Age 3 to Guzhangian (~521–497 Ma). cf, Non-metric multidimensional scaling ordination of genus occurrences of Cambrian BST biotas. Biotas of different ages are depicted as colourful symbols. Genera are shown in light grey text. c, d, Results from using Jaccard index. e, f, Results from using Ochiai index. c, e, Singletons of genera included. d, f, Singletons of genera excluded. g, h, Species composition of phyla and sub-phylum groups in Cambrian BST biotas. g, Species proportion. h, Species richness. Results in b adapted with permission from ref. 56, reproduced under a Creative Commons licence CC BY 4.0.

Supplementary information

Supplementary Information

Supplementary Discussion and references (including references for the Supplementary Discussion and Supplementary Tables 2 and 3).

Reporting Summary

Supplementary Table 1

Community data of the Renkupo Quarry of Huayuan biota and quarries of other Cambrian Burgess Shale-type deposits. The table includes species occurrence data from the quarries of the Huayuan (Renkupo), Chengjiang (Mafang, Shankou, and Haiyan), Qingjiang (Jinyangkou) and Burgess Shale (Walcott, Raymond, Marble Canyon, and Tulip Bed) biotas. Data for each species includes its lifestyle and specimen count.

Supplementary Table 2

Spatiotemporal data of early to middle Cambrian Burgess Shale-type deposits. Data for each deposit includes its stratigraphic context, geographic information and key references. See references listed in the Supplementary References.

Supplementary Table 3

Spatiotemporal data of early to middle Cambrian Burgess Shale-type deposits. Data for each deposit includes its stratigraphic context, geographic information and key references. See references listed in the Supplementary References.

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Zeng, H., Liu, Q., Zhao, F. et al. A Cambrian soft-bodied biota after the first Phanerozoic mass extinction.
Nature (2026). https://doi.org/10.1038/s41586-025-10030-0

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