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Cited by 187Paleontology and Stratigraphy of FossilsPaleontology and Evolutionary BiologyEvolution and Paleontology Studies

Precambrian animal diversity: Putative phosphatized embryos from the Doushantuo Formation of China

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Chen, Jun-Yuan, Oliveri, Paola, Li, Chia-Wei, Zhou, Gui-Qing, Gao, Feng, Hagadorn, James W., Peterson, Kevin J., Davidson, Eric H.·2000·Proceedings of the National Academy of Sciences
DOI 10.1073/pnas.97.9.4457PMC PMC18256
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Abstract

Putative fossil embryos and larvae from the Precambrian phosphorite rocks of the Doushantuo Formation in Southwest China have been examined in thin section by bright field and polarized light microscopy. Although we cannot completely exclude a nonbiological or nonmetazoan origin, we identified what appear to be modern cnidarian developmental stages, including both anthozoan planula larvae and hydrozoan embryos. Most importantly, the sections contain a variety of small (≤200 μm) structures that greatly resemble gastrula stage embryos of modern bilaterian forms.

AI snapshot

Written from the paper’s full text.

TL;DR

Thin-section microscopy of phosphorites from the Doushantuo Formation revealed putative fossil embryos and larvae resembling modern cnidarian and bilaterian gastrulae, including small ≤200 μm forms. The authors argue these may extend cnidarian and bilaterian evolutionary history deeper into the Precambrian, while acknowledging that a nonbiological or nonmetazoan origin cannot be completely excluded.

Key findings

  • The sections contain what appear to be modern cnidarian developmental stages, including anthozoan planula larvae and hydrozoan embryos, plus small (≤200 μm) structures resembling gastrula-stage embryos of modern bilaterian forms.
  • Bilaterian-like gastrulae are typically 150–200 μm in diameter; in three deuterostome embryo-like specimens, the archenteron diameter was 27 ± 3% of the average external diameter, and cnidarian-like embryo wall thicknesses were consistently similar.
  • About 2,000 thin sections were examined and over 4,000 digital images of embryos and larvae were recorded; each reported morphotype was encountered multiple times.
  • The Doushantuo Formation could be as old as 580 Ma, pending direct measurement within 570 ± 20 Ma, and is likely to precede the lowest strata with which bilaterian remains have so far been associated.

Methods

  • Samples were collected from the Wusi and Baidoushan quarries of the Weng’an phosphate mine; thin sections were 30–50 μm thick and examined by transmitted light microscopy at ×100 or ×200 magnification, with selected samples viewed in cross-polarized light with a gypsum plate.
  • About 2,000 sections were examined, over 4,000 digital images of embryos and larvae were recorded, and morphometric measurements were taken from photographic representations and converted to μm by reference to size standards.

Limitations

  • Stated: the authors cannot completely exclude a nonbiological or nonmetazoan origin, and it remains formally possible that only some aspects of the fossils are biogenic—perhaps not even metazoan—while other features are nonbiogenic.
  • Stated: this is an initial analysis; the actual diversity of bilaterian forms can be established only by examination of later developmental stages, if they can be recovered, and taxonomic assignments are tentative; more extensive morphometric measurements are forthcoming.
  • Evident: the study is from one particular location/deposit and relies on morphological resemblance to modern embryos, with no direct molecular or adult-form evidence reported.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1073/pnas.97.9.4457

Cites

43 of 43 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 29 cited sources checked · 0 supported · 0 flagged

  • Findingown data
    § Methods

    The dimensional consistency of each morphotype is fairly remarkable.

    “considering the complexity of the mineralization process, the dimensional consistency of each type is fairly remarkable.”
    Quote in the paperNot a substantial claim
  • Findingown data
    § Methods

    The fossil in Fig. 2A is strikingly similar to an early anthozoan planula.

    “Fig. 2A shows a form strikingly similar to an early anthozoan planula.”
    Quote in the paperSubstantial claim
  • Findingown data
    § Discussion

    Individual contiguous cells appear to have been reconstituted as individual crystals, seen in polarized light in different colors.

    “In several of the images, individual contiguous cells appear to have been reconstituted as individual crystals, seen in polarized light in different colors, because their axes are noncoincident (Figs. 2F, 3D, and 4F).”
    Quote in the paperSubstantial claim
  • Findingown data
    § Methods

    The structures shown in Fig. 3 A-G resemble embryos of the echinoderm-hemichordate clade of the deuterostomes.

    “The structures shown in Fig. 3 A–G resemble embryos of the echinoderm-hemichordate clade of the deuterostomes, as illustrated by the sea urchin example in Fig. 3H.”
    Quote in the paperSubstantial claim
  • Findingown data
    § Discussion

    The orientations of the crystals in what look to be the endodermal and ectodermal cell layers of the embryo are in several places the same.

    “In Fig. 2D, for example, the orientations of the crystals in what look to be the endodermal and ectodermal cell layers of the embryo are in several places the same, as indicated by the similar colors (arrows).”
    Quote in the paperSubstantial claim
  • May combine two claims. 9
  • Classified as probably not a substantial claim. 3
  • The quote only partly states this claim. 1

  • May combine two claims.

    Findingown data
    § Discussion

    There is so far no evidence of embryos of bilaterian nature in the Doushantuo phosphorites that are more than 250 μm in diameter, or that have forms which support the possibility of direct development.

    “However, there is so far no evidence of embryos of bilaterian nature in the Doushantuo phosphorites that are more than 250 μm in diameter, or that have forms which support the possibility of direct development”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Discussion

    Various forms that were seen cannot immediately be identified by similarity to modern models, and an example is shown in Fig. 4D; its affinities are problematic.

    “Various forms that we saw cannot immediately be identified by similarity to modern models, and an example is shown in Fig. 4D; its affinities are problematic.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data
    § Methods

    The thickness of both the apparent endodermal inner layer and the average thickness of outer wall in all of the cnidarian-like embryos were always the same.

    “and the thickness of both the apparent endodermal inner layer, and the average thickness of outer wall in all of the cniderian-like embryos, were always the same.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data
    § Discussion

    The coated grains are dissimilar to one another in size, crystal structure, number of laminations, and lamination thickness.

    “These coated grains are dissimilar to one another in size, crystal structure, number of laminations, and lamination thickness.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingreasoning
    § Discussion

    The structures appear to be bounded by single cell-thick walls that enclose blastocoelar spaces of familiar dimension; the bilaterian-like forms display archenterons; and the cnidarian-like forms other typical endodermal morphologies.

    “The structures appear to be bounded by single cell-thick walls that enclose blastocoelar spaces of familiar dimension; the bilaterian-like forms display archenterons; and the cnidarian-like forms other typical endodermal morphologies.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Findingown data
    § Discussion

    The large blastocoel and the characteristic deuterostome archenterons are particularly clear in Fig. 3 A, C, and G.

    “The large blastocoel and the characteristic deuterostome archenterons are particularly clear in Fig. 3 A, C, and G.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Methods

    The Fig. 3 forms are typically 150-200 μm in diameter, similar to many echinoderm and hemichordate embryos, and to molluscan, polychaete, and other lophotrochozoan embryos.

    “Note first that these are all rather small forms, typically 150–200 μm in diameter, similar to many echinoderm and hemichordate embryos, and to molluscan, polychaete, and a good many other lophotrochozoan embryos.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data
    § Methods

    The objects described in Figs. 2 and 3 are fossilized embryos that originally were composed of epithelial layers of cells surrounding internal cellular structures that arose by invagination.

    “As we summarize in Discussion, the results of the polarized and bright-field microscopy are consistent with the argument that the objects described in Figs. 2 and 3 are indeed fossilized embryos, which originally were composed of epithelial layers of cells surrounding internal cellular structures that arose by invagination.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Constant morphology and constant dimension are outputs of genetically controlled developmental systems and are a powerful index of biological origin.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § Abstract

    Microfaunal bilaterian stem groups must have evolved through several stages of regulatory complexity during Precambrian time.

    “arguments based on regulatory evolution lead to the proposition that microfaunal bilaterian stem groups must have evolved through several stages of regulatory complexity during Precambrian time (17, 18).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [17] Davidson E H, Peterson K J, Cameron R A. Science. 1995;270:1319–1325. doi: 10.1126/science.270.5240.1319. [DOI] [PubMed] [Google Scholar] source

      Not checked in the free run.

    • cites [18] Peterson K J, Davidson E H. Proc Natl Acad Sci USA. 2000;97:4487–4492. doi: 10.1073/pnas.97.9.4487. [DOI] [PMC free article] [PubMed] [Google Scholar] source

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data
    § Discussion

    The original structure from which the fossil formed was soft, for its external wall is deformed by a hard grain against which it still lies.

    “In Fig. 3 A and B, we can see that the original structure from which the fossil formed was soft, for its external wall is deformed by a hard grain against which it still lies (arrow).”
    Quote in the paperSubstantial claim

  • The quote only partly states this claim.

    Interpretationreasoning
    § Discussion

    The Precambrian embryonic organisms of bilaterian form discussed here almost certainly developed indirectly, using planktotrophic larval forms.

    “If the Precambrian embryonic organisms of bilaterian form discussed here developed into organisms that we could recognize as similar to adult bilaterian forms, they almost certainly did so indirectly, using planktotrophic larval forms.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Morphological resemblance between fossil structures and modern developmental stages is a reliable indicator of biological affinity.

  • May combine two claims.

    Interpretationown data
    § Discussion

    Organisms that produced embryos of bilaterian affinity, as well as clearly differentiated cnidarian forms, may have existed some millions of years earlier than indicated by any previous paleontological evidence.

    “The claim made in this paper is that organisms that produced embryos of bilaterian affinity, as well as clearly differentiated cnidarian forms, may have existed some millions of years earlier than indicated by any previous paleontological evidence.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The fossil embryos in Fig. 3 are real (authentic fossils).
    • Rests on an assumption: Constant morphology and constant dimension are outputs of genetically controlled developmental systems and are a powerful index of biological origin.

  • May combine two claims.

    Premisecitation
    § Discussion

    For deuterostomes and lophotrochozoans, maximal indirect development is primitive, and direct development is derived.

    “Many lines of evidence show that for deuterostomes and lophotrochozoans maximal indirect development is primitive, and direct development is derived (36–38).”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [36] Peterson K J, Cameron R A, Davidson E H. BioEssays. 1997;19:623–631. doi: 10.1002/bies.950190713. [DOI] [PubMed] [Google Scholar] source

      Not checked in the free run.

    • cites [37] Peterson K J, Cameron R A, Davidson E H. Dev Biol. 2000;219:1–17. doi: 10.1006/dbio.1999.9475. [DOI] [PubMed] [Google Scholar] source

      Not checked in the free run.

    • cites [38] Nielsen C. Biol Rev Camb Philos Soc. 1998;73:125–155. [Google Scholar]

      Not checked in the free run.

13 of 13

  • The authors state this as an assumption.

    The fossil embryos in Fig. 3 are real (authentic fossils).

    “In any case, assuming that they are indeed real, the bilaterian nature of the fossil embryos in Fig. 3 is hard to doubt.”

  • The paper relies on this without support.

    Constant morphology and constant dimension are outputs of genetically controlled developmental systems and are a powerful index of biological origin.

    “Constant morphology and constant dimension are the outputs of genetically controlled developmental systems and are thus a powerful index of biological origin.”

  • The paper relies on this without support.

    Morphological resemblance between fossil structures and modern developmental stages is a reliable indicator of biological affinity.

    “The comparisons with modern forms in Fig. 3 are intended only to show that the morphological characters of the fossil gastrulae are paralleled in detail by those of modern bilaterian gastrulae.”
3 of 3

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • There is clear evidence for the prevalence of sponges and cnidarians in the Doushantuo and Ediacaran assemblages.

    “and indeed there is clear evidence for the prevalence of sponges and cnidarians from both the Doushantuo and Ediacaran assemblages (Gehling and Rigby, 1996;Brasier et al., 1997;Chen et al., 2000;Xiao et al., 2000;Chen et al., 2002).”

    From The last common bilaterian ancestor (2002) · cites this paper as Chen et al., 2000

    The Methods and Discussion report apparent cnidarian forms and microscopic sponges in Doushantuo samples, though the authors caution that the fossil interpretations are not certain. The paper does not establish their prevalence across the Doushantuo assemblage; its background discussion describes the affinities of Ediacaran remains as enigmatic rather than establishing a prevalence of sponges and cnidarians there. Page numbers were not available in our copy. (LLM, conf=0.86)

    Experimental — accuracy not yet measured

  • The Doushantuo phosphorites have a high capacity to preserve very fine biological structures, including cellular and subcellular details.

    “A number of studies have shown that the Doushantuo phosphorites have a high potential for preservation of very fine biological detail, including cellular and even subcellular structures (e.g., Xiao et al., 1998;Li et al., 1998;Chen et al., 2000).”

    From Precambrian Animal Life: Probable Developmental and Adult Cnidarian Forms from Southwest China (2002) · cites this paper as Chen et al., 2000

  • Putative gastrulae among the smaller embryonic microfossils are single cell-thick structures whose morphology and dimensions closely resemble some modern bilaterian gastrulae.

    “Among these are putative gastrulae, which appear to be marvelously preserved, single cell-thick structures the morphology and dimensions of which bear remarkable resemblance to some modern bilaterian gastrulae.”

    From Precambrian Animal Life: Probable Developmental and Adult Cnidarian Forms from Southwest China (2002) · cites this paper as Chen et al., 2000

  • The sole fossil evidence possibly linked to earlier bilaterians is a set of puzzling gastrula-stage embryo microfossils from the Doushantuo Formation in Southwest China.

    “The only fossil evidence that would appear to relate to earlier bilaterian forms consists of still enigmatic microfossils of gastrula-stage embryos from the Doushantuo formation of Southwest China (Chen et al., 2000).”

    From Precambrian Animal Life: Probable Developmental and Adult Cnidarian Forms from Southwest China (2002) · cites this paper as Chen et al., 2000

  • Other classes of gastrula-like microfossils reported by Chen et al. (2000) resemble gastrular and planular forms of some modern cnidarians.

    “Other classes of gastrula-like microfossil reported by Chen et al. (2000) resemble the gastrular and planular forms of some modern cnidarians.”

    From Precambrian Animal Life: Probable Developmental and Adult Cnidarian Forms from Southwest China (2002) · cites this paper as Chen et al., 2000

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Cnidarian-like embryo wall thicknesses are not always the same

    Minor

    The text says the inner-layer and average outer-wall thicknesses were always the same. Table 1 instead lists inner walls ranging from 6.7 to 9.0 μm and outer walls ranging from 9.0 to 18 μm.

1 of 1

Cites

Flagged first, then by citations

1 of the 44 references couldn’t be matched to a known paper.

Research works printed but not linked: 10

  1. J-Y Chen, G-Q Zhou The Cambrian Explosion and the Fossil Record (Bulletin of the National Museum of Natural Science), eds J-Y Chen, Y N Cheng, H V Iten (National Museum of Natural History, Taichung) 10, 11–105 (1997).
  2. S Bengtson, S Conway Morris, B J Cooper, P A Jell, B N Runnegar Mem Ass Australas Palaeontols 9, 1–364 (1990).
  3. M A Fedonkin Early Life on Earth: Nobel Symposium No. 84, ed S Bengtson (Columbia Univ. Press, New York), pp. 370–388 (1994).
  4. J G Gehling, G M Narbonne, S Jensen, M L Droser Geol Soc Am Abstr Prog 31, 362 (1999).
  5. Y Qian, M Chen, Y Chen Acta Paleont Sinica 18, 207–232 (1979).
  6. Y Xing, Q Ding, H Luo, T He, Y Wang Chin Acad Geol Sci 7, 1–262 (1984).
  7. Y Zhang, L Yin, S Xiao, A H Knoll Paleont Soc Mem 50, 1–52 (1998).
  8. G Shields Eclogae Geol Helv 92, 221–233 (1999).
  9. Z Zhao, Y Xing, G Ma, Y Chen Biostratigraphy of the Yangtze Gorge Area, (1) Sinian (Geological Publishing House, Beijing, 1985).
  10. J-P Chevalier Traité de Zoologie, ed P-P Grassé (Masson, Paris), pp. 403–764 (1987).

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Related

Authors
Chen, J.-Y., Oliveri, P., Li, C.-W., Zhou, G.-Q., Gao, F., Hagadorn, J. W., Peterson, K. J., & Davidson, E. H.
Affiliations
  • Nanjing Institute of Geology and Paleontology, Nanjing 210008, China; Divisions of Biology and Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125; and Department of Life Sciences, National Tsing Hua University, Hsinchu 300, Taiwan, China
  • California Institute of Technology (US)
ORCID
Venue
Proceedings of the National Academy of Sciences
Publisher
National Academy of Sciences
Published
2000-04-25
Volume
97
Issue
9
Pages
4457-4462
ISSN
  • 0027-8424 (ISSN-L)
  • 1091-6490
DOI
10.1073/pnas.97.9.4457
PMC
PMC18256
OpenAlex
W2165010994
Semantic Scholar
5a119f690dd07be08df8dda9f1c40d3fe5b44191
Cited by
187
References
44
Citations by year
2026: 1 · 2025: 1 · 2024: 3 · 2023: 2 · 2022: 7 · 2021: 1 · 2020: 2 · 2019: 7 · 2018: 3 · 2017: 4 · 2016: 7 · 2015: 7 · 2014: 6 · 2013: 8 · 2012: 5
FWCI
9.01
Type
journal article
Language
en
Open access
Locations
  • Proceedings of the National Academy of Sciences (publishedVersion)
  • Europe PMC (PubMed Central) (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
  • CaltechAUTHORS (California Institute of Technology) (submittedVersion)
  • UCL Discovery (University College London) (submittedVersion)
Topics
  • Physical Sciences › Earth and Planetary Sciences › Paleontology › Paleontology and Stratigraphy of Fossils
  • Physical Sciences › Earth and Planetary Sciences › Paleontology › Paleontology and Evolutionary Biology
  • Physical Sciences › Earth and Planetary Sciences › Paleontology › Evolution and Paleontology Studies
Keywords
Doushantuo Formation, phosphate rock, fossil embryos, early animal evolution, Precambrian fossils
MeSH terms
Animals, China, Cnidaria, Embryo, Nonmammalian, Biological Evolution, Fossils, Gastrula, Paleontology, Genetic Variation, Body Patterning

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