The DOI matches its Crossref record; 43 of the 44 references it cites were found in a registry or an index; none of the 29 sources its claims cite is checked for support yet.
Precambrian animal diversity: Putative phosphatized embryos from the Doushantuo Formation of China
Open accessAbstract
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.
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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.
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22 Own result · 11 Own interpretation · 10 Not checked yet · 2 No basis given · 1 Own method
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“considering the complexity of the mineralization process, the dimensional consistency of each type is fairly remarkable.”
plainn = 3- Asserted: passes — The authors put it forward as true.
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“Fig. 2A shows a form strikingly similar to an early anthozoan planula.”
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“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).”
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“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.”
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“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).”
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In the paper
“Although oncoids occur in these sections (although quite rarely, compared with fossil embryos), their concentric, often laminar structures appear quite different from those of the putative fossil embryos when viewed in polarized light.”
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“For example, the fraction of the average external diameter constituted by the diameter of the archenteron in the three deuterostome embryo-like specimens is 27 ± 3%”
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In the paper
“The main feature of the polarized and bright-field image pairs in Figs. 2 and 3 is that the morphology of the putative fossil embryos looks the same by either display.”
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In the paper
“Fig. 3 shows a remarkable series of what appear to be fossil embryos that display specific characteristics of modern bilaterian gastrula-stage embryos, specifically those of many phyla of modern marine invertebrates.”
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“Throughout most of the polarized light images, large contiguous patches of cells constituting a given epithelial layer generally display the same crystal orientation.”
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In the paper
“Fig. 3 I and J shows what could be different forms of fossil gastrulae. These display more of a spiralian character, illustrated by the drawings of polychaete embryos shown in Fig. 3K.”
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In the paper
“The blastocoelar space and the lumen of the archenteron are amorphous, rather than crystalline, because they appear black in polarized light however the prisms are set.”
plainSingle case- Asserted: passes — The authors put it forward as true.
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In the paper
“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.”
hedged- Asserted: passes — The authors put it forward as true.
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In the paper
“The polarized light image in Fig. 2D reveals the same features; therefore, the crystal elements of which the structural elements we interpret as ectodermal and archenteron walls are composed do not extend beyond the limits visible in white light (i.e., they are not merely color discontinuities in a solid mineral grain).”
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In the paper
“Fig. 2 C and D shows a fossil that displays a unique morphology found in some modern hydrozoan gastrula-stage embryos.”
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In the paper
“Most importantly, the sections contain a variety of small (≤200 μm) structures that greatly resemble gastrula stage embryos of modern bilaterian forms.”
plain- Asserted: passes — The authors put it forward as true.
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In the paper
“Furthermore, as Table 1 illustrates, the dimensions of each type are always approximately the same.”
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“Cladistic analyses, both morphological and molecular, clearly indicate that the bilaterians are monophyletic, i.e., they derive from a latest common ancestor that gave rise only to bilaterians (see ref. 8).”
What the sources say
- Not checked yetcites [8] Adoutte A. Proc Natl Acad Sci USA. 2000;97:4453–4456. doi: 10.1073/pnas.97.9.4453. [DOI] [PMC free article] [PubMed] [Google Scholar] source
boosted- Asserted: passes — The authors put it forward as true.
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In the paper
“In addition to replacing carbonate sediments, soft tissues of metazoan embryos, larvae, adults, and algae also appear to have been mineralized (26–29).”
What the sources say
- Not checked yetcites [26] Li C-W, Chen J-Y, Hua T-E. Science. 1998;279:879–882. doi: 10.1126/science.279.5352.879. [DOI] [PubMed] [Google Scholar] source
- Not checked yetcites [27] Xiao S, Zhang Y, Knoll A H. Nature (London) 1998;391:553–558. [Google Scholar] source
- Not checked yetcites [28] Zhang Y, Yin L, Xiao S, Knoll A H. Paleont Soc Mem. 1998;50:1–52. [Google Scholar]
- Not checked yetcites [29] Xunlai Y, Hofmann H J. Alcheringa. 1998;22:189–222. [Google Scholar] source
hedged- Asserted: passes — The authors put it forward as true.
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In the paper
“The latest Precambrian also has yielded trace fossils of unmistakable bilaterian origin (5–7).”
What the sources say
- Not checked yetcites [5] Grotzinger J P, Bowring S A, Saylor B Z, Kaufman A J. Science. 1995;270:598–604. [Google Scholar] source
- Not checked yetcites [6] Fedonkin M A, Wagoner B M. Nature (London) 1997;388:868–871. [Google Scholar] source
- Not checked yetcites [7] Fedonkin M A. In: Early Life on Earth: Nobel Symposium No. 84. Bengtson S, editor. New York: Columbia Univ. Press; 1994. pp. 370–388. [Google Scholar]
boosted- Asserted: passes — The authors put it forward as true.
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In the paper
“But on molecular and phylogenetic as well as paleontological bases, it is already likely that the bilaterians have an evolutionary history that long precedes the Ediacaran, let alone the Cambrian “explosion.””
hedged- Asserted: passes — The authors put it forward as true.
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In the paper
“It is important to stress, however, that whatever the absolute time horizon represented by the Doushantuo Fm, it is likely to precede the lowest strata with which bilaterian remains have so far been associated (20).”
What the sources say
- Not checked yetcites [20] Gehling J G, Narbonne G M, Jensen S, Droser M L. Geol Soc Am Abstr Prog. 1999;31:362. [Google Scholar]
hedged- Asserted: passes — The authors put it forward as true.
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In the paper
“Each of the types we have categorized in Figs. 2 and 3 have been seen multiple times in the sections examined.”
plain- Asserted: passes — The authors put it forward as true.
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In the paper
“This study suggests that the evolutionary history of both cnidarian and bilaterian forms may extend many millions of years deeper in Precambrian time than previous direct evidence so far indicates.”
hedgedconditional- Asserted: passes — The authors put it forward as true.
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- 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.
None of the sources cited for this claim have been checked yet.
In the paper
“The age of the Doushantuo Fm could be as old as 580 Ma (26), and pending direct measurement, its age must fall within the range 570 ± 20 Ma (27) [Saylor et al. (34) argue that it is toward the younger end of this range].”
What the sources say
- Not checked yetcites [26] Li C-W, Chen J-Y, Hua T-E. Science. 1998;279:879–882. doi: 10.1126/science.279.5352.879. [DOI] [PubMed] [Google Scholar] source
- Not checked yetcites [27] Xiao S, Zhang Y, Knoll A H. Nature (London) 1998;391:553–558. [Google Scholar] source
- Not checked yetcites [34] Saylor B Z, Kaufman A J, Grotzinger J P, Urban F. J Sediment Res. 1998;68:1223–1235. doi: 10.2110/jsr.68.1223. [DOI] [PubMed] [Google Scholar] source
hedged- Asserted: passes — The authors put it forward as true.
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In the paper
“However, we think the initial evidence presented here implies that embryos of diverse metazoan affinity were in fact present several tens of millions of years before the onset of the Cambrian.”
hedged- Asserted: passes — The authors put it forward as true.
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- 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.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“These remains indicate that major evolutionary diversification of animals already had occurred by the onset of the Cambrian, and, therefore, more remote ancestral forms must have been alive earlier.”
hedged- Asserted: passes — The authors put it forward as true.
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In the paper
“Furthermore, to accommodate the diversity of the fossil gastrulae both deuterostome and spiralian models appear to be required.”
hedgedconditional- Asserted: passes — The authors put it forward as true.
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- Rests on an assumption: Morphological resemblance between fossil structures and modern developmental stages is a reliable indicator of biological affinity.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“These remains indicate that major evolutionary diversification of animals already had occurred by the onset of the Cambrian, and, therefore, more remote ancestral forms must have been alive earlier.”
plaindirect- Asserted: passes — The authors put it forward as true.
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A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“In any case, assuming that they are indeed real, the bilaterian nature of the fossil embryos in Fig. 3 is hard to doubt.”
hedged- Asserted: passes — The authors put it forward as true.
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- The authors state this as an assumption: The fossil embryos in Fig. 3 are real (authentic fossils).
- Rests on an assumption: Morphological resemblance between fossil structures and modern developmental stages is a reliable indicator of biological affinity.
In the paper
“The most general and important of these arguments is that almost all major bilaterian clades already are represented in the Lower Cambrian, in remarkably preserved deposits such as the Chengjiang fossil lagerstätte (1).”
What the sources say
- Not checked yetcites [1] Chen J-Y, Zhou G-Q. In: The Cambrian Explosion and the Fossil Record (Bulletin of the National Museum of Natural Science) Chen J-Y, Cheng Y N, Iten H V, editors. Vol. 10. Taichung: National Museum of Natural History; 1997. pp. 11–105. [Google Scholar]
plain- Asserted: passes — The authors put it forward as true.
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None of the sources cited for this claim have been checked yet.
In the paper
“Molecular phylogenies based on sequence comparisons of protein domains shared by all bilaterians suggest that the time of divergence of these proteins may extend back to 600–1,200 million years (megaannuum; Ma) ago (11–16).”
What the sources say
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hedgedconditional- Asserted: passes — The authors put it forward as true.
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None of the sources cited for this claim have been checked yet.
In the paper
“But thus far, unequivocal paleontological evidence of bilaterian forms has extended only to the final period of the Neoproterozoic, a few million years before the Cambrian “explosion” (5–7, 19, 20).”
What the sources say
- Not checked yetcites [5] Grotzinger J P, Bowring S A, Saylor B Z, Kaufman A J. Science. 1995;270:598–604. [Google Scholar] source
- Not checked yetcites [6] Fedonkin M A, Wagoner B M. Nature (London) 1997;388:868–871. [Google Scholar] source
- Not checked yetcites [7] Fedonkin M A. In: Early Life on Earth: Nobel Symposium No. 84. Bengtson S, editor. New York: Columbia Univ. Press; 1994. pp. 370–388. [Google Scholar]
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- Not checked yetcites [20] Gehling J G, Narbonne G M, Jensen S, Droser M L. Geol Soc Am Abstr Prog. 1999;31:362. [Google Scholar]
plain- Asserted: passes — The authors put it forward as true.
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A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“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”
hedged- Asserted: passes — The authors put it forward as true.
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A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“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.”
plainSingle case- Asserted: passes — The authors put it forward as true.
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A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“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.”
plain- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. The paper’s conclusions may not depend on it.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“These coated grains are dissimilar to one another in size, crystal structure, number of laminations, and lamination thickness.”
plain- Asserted: passes — The authors put it forward as true.
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It may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“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.”
hedged- Asserted: passes — The authors put it forward as true.
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It may state two separate claims as one.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The large blastocoel and the characteristic deuterostome archenterons are particularly clear in Fig. 3 A, C, and G.”
boosted- Asserted: passes — The authors put it forward as true.
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- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“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.”
plaincorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“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.”
hedged- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
- Rests on an assumption: Constant morphology and constant dimension are outputs of genetically controlled developmental systems and are a powerful index of biological origin.
None of the sources cited for this claim have been checked yet.
In the paper
“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).”
What the sources say
- Not checked yetcites [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 yetcites [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
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“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).”
plaindirectSingle case- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“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.”
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
The quote only partly states this claim.
- Rests on an assumption: Morphological resemblance between fossil structures and modern developmental stages is a reliable indicator of biological affinity.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“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.”
hedged- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
- 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.
None of the sources cited for this claim have been checked yet.
In the paper
“Many lines of evidence show that for deuterostomes and lophotrochozoans maximal indirect development is primitive, and direct development is derived (36–38).”
What the sources say
- Not checked yetcites [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 yetcites [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 yetcites [38] Nielsen C. Biol Rev Camb Philos Soc. 1998;73:125–155. [Google Scholar]
boosted- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
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.”
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?
The source backs part of the claim, not all of it — or backs it for a different population, condition or comparison.
In the citing paper
“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
Experimental — accuracy not yet measuredIn the citing paper
“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
In the citing paper
“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
In the citing paper
“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
In the citing paper
“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
In the citing paper
“The age of these microfossils is likely to be between 570 and 580 mya, i.e., 25-35 my prior to the onset of the Cambrian (Fig. 1).”
From Precambrian Animal Life: Probable Developmental and Adult Cnidarian Forms from Southwest China (2002) · cites this paper as Chen et al., 2000
In the citing paper
“It might be noted that the embryos we describe here, like those of Chen et al. (2000) are not particularly small; they fall within the range of modern examples.”
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.
Rated minor: it would not touch a result — a value no result rests on, a p-value that stays on the same side of the significance level, or a conflict that is clerical, resolved elsewhere in the paper, or outside its own findings.
In the paper
§ Methods
“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.”
§ Methods
“Fig. 2 A 234 × 333 13.4 9.0 * — 207 × 252 13.5 — — 234 × 234 13.5 9.0 * — 252 × 297 9.0 9.0 * — Fig. 2 C 140 × 140 13.4 6.7 — 126 × 142 13.4 8.0 — 135 × 144 13.5; 18 † 9.0 —”
Citations
Cites
Evidence for a clade of nematodes, arthropods and other moulting animals
Aguinaldo, A. M. A., Turbeville, J. M., Linford, L. S., Rivera, M. C., Garey, J. R., Raff, R. A., & Lake, J. A. (1997) · Nature · doi:10.1038/387489a0 · Cited by 1,609
Reproduction of Marine Invertebrates
(1979) · Elsevier eBooks · doi:10.1016/b978-0-12-282505-7.x5001-5 · Cited by 1,268
Three-dimensional preservation of algae and animal embryos in a Neoproterozoic phosphorite
Xiao, S., Zhang, Y., & Knoll, A. H. (1998) · Nature · doi:10.1038/35318 · Cited by 783
Biostratigraphic and Geochronologic Constraints on Early Animal Evolution
Grotzinger, J. P., Bowring, S. A., Saylor, B. Z., & Kaufman, A. J. (1995) · Science · doi:10.1126/science.270.5236.598 · Cited by 701
Embryology and Phylogeny in Annelids and Arthropods
(1973) · Elsevier eBooks · doi:10.1016/c2013-0-05626-5 · Cited by 535
Reproduction of marine invertebrates
Dales, R. P. (1974) · Nature · doi:10.1038/251556b0 · Cited by 531
Calibrating Rates of Early Cambrian Evolution
Bowring, S. A., Grotzinger, J. P., Isachsen, C. E., Knoll, A. H., Pelechaty, S. M., & Kolosov, P. (1993) · Science · doi:10.1126/science.11539488 · Cited by 524
The new animal phylogeny: Reliability and implications
Adoutte, A., Balavoine, G., Lartillot, N., Lespinet, O., Prud'homme, B., & de Rosa, R. (2000) · Proceedings of the National Academy of Sciences · doi:10.1073/pnas.97.9.4453 · Cited by 512
Molecular Evidence for Deep Precambrian Divergences Among Metazoan Phyla
Wray, G. A., Levinton, J. S., & Shapiro, L. H. (1996) · Science · doi:10.1126/science.274.5287.568 · Cited by 511
Wang, D. Y.-C., Kumar, S., & Hedges, S. B. (1999) · Proceedings of the Royal Society of London. Series B: Biological Sciences · doi:10.1098/rspb.1999.0617 · Cited by 493
Research works printed but not linked: 10
- 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).
- S Bengtson, S Conway Morris, B J Cooper, P A Jell, B N Runnegar Mem Ass Australas Palaeontols 9, 1–364 (1990).
- M A Fedonkin Early Life on Earth: Nobel Symposium No. 84, ed S Bengtson (Columbia Univ. Press, New York), pp. 370–388 (1994).
- J G Gehling, G M Narbonne, S Jensen, M L Droser Geol Soc Am Abstr Prog 31, 362 (1999).
- Y Qian, M Chen, Y Chen Acta Paleont Sinica 18, 207–232 (1979).
- Y Xing, Q Ding, H Luo, T He, Y Wang Chin Acad Geol Sci 7, 1–262 (1984).
- Y Zhang, L Yin, S Xiao, A H Knoll Paleont Soc Mem 50, 1–52 (1998).
- G Shields Eclogae Geol Helv 92, 221–233 (1999).
- Z Zhao, Y Xing, G Ma, Y Chen Biostratigraphy of the Yangtze Gorge Area, (1) Sinian (Geological Publishing House, Beijing, 1985).
- J-P Chevalier Traité de Zoologie, ed P-P Grassé (Masson, Paris), pp. 403–764 (1987).
Cited by
Sorted by citations
Peterson, K. J., & Eernisse, D. J. (2001) · Evolution & Development · doi:10.1046/j.1525-142x.2001.003003170.x · Cited by 529
Self-citationSteiner, M., Li, G., Qian, Y., Zhu, M., & Erdtmann, B.-D. (2007) · Palaeogeography, Palaeoclimatology, Palaeoecology · doi:10.1016/j.palaeo.2007.03.046 · Cited by 479
Molecular Phylogeny and Divergence Times of Deuterostome Animals
Blair, J. E., & Hedges, S. B. (2005) · Molecular Biology and Evolution · doi:10.1093/molbev/msi225 · Cited by 451
Integrated Ediacaran (Sinian) chronostratigraphy of South China
Zhu, M., Zhang, J., & Yang, A. (2007) · Palaeogeography Palaeoclimatology Palaeoecology · doi:10.1016/j.palaeo.2007.03.025 · Cited by 434
The last common bilaterian ancestor
Erwin, D. H., & Davidson, E. H. (2002) · Development · doi:10.1242/dev.129.13.3021 · Cited by 320
Self-citation
Metadata
- 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)
- 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
- 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
- green
- europepmc.org
- 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
About these checks
Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.
A language model drew the claims from the paper on 2026-10-06, under version 3 of the claim definition (model deepseek-v4.1-flash, prompt extract-v3).
A second model labelled each claim on 2026-10-06 (model jev-1.13-20260917, definition revision gold-guideline-v0.2).
Statistics and arithmetic are recomputed, not judged.
Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.
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