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Cited by 324Developmental Biology and Gene RegulationMarine Invertebrate Physiology and EcologyPhilosophy and History of Science

The last common bilaterian ancestor

Open access
Erwin, Douglas H., Davidson, Eric H.·2002·Development
DOI 10.1242/dev.129.13.3021
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Abstract

Many regulatory genes appear to be utilized in at least superficially similar ways in the development of particular body parts in Drosophila and in chordates. These similarities have been widely interpreted as functional homologies, producing the conventional view of the last common protostome-deuterostome ancestor (PDA) as a complex organism that possessed some of the same body parts as modern bilaterians. Here we discuss an alternative view, in which the last common PDA had a less complex body plan than is frequently conceived. This reconstruction alters expectations for Neoproterozoic fossil remains that could illustrate the pathways of bilaterian evolution.

Integrity signals

Registry

Crossref · 10.1242/dev.129.13.3021

Cites

150 of 150 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

4 of 36 cited sources checked · 1 supported · 0 flagged · accuracy not yet measured

  • Premisecitation

    Molecular clock estimates mostly place the latest PDA much deeper in time than the latest Neoproterozoic, with dates ranging from 600 to 1200 Mya depending on proteins, calibration points, and substitution models.

    “Depending on the proteins, calibration points and rate substitution models used, these estimates range from 600 to 1200 Mya (Wray et al., 1996;Ayala et al., 1998;Bromham et al., 1998;Gu, 1998;Cutler, 2000).”
    Quote in the paperSubstantial claim1 of 3 sources checked
    • cites Wray et al., 1996 source
    • cites Ayala et al., 1998 source
    • cites Bromham et al., 1998 source

      The Results report divergence estimates older than 680 Ma and say estimates differ between the two sequence datasets; the Methods also describe multiple fossil calibrations and a substitution model. But the paper does not give the attributed 600–1200 Ma range, and its estimates have wide confidence intervals rather than precise dates. The cited paper therefore supports the general point about older, method-dependent molecular dates, not the stated range. (LLM, conf=0.84)

      Experimental — accuracy not yet measured
    • Rests on an assumption: Molecular clock estimates, despite potential problems, are reliable enough to indicate that the latest PDA is much older than the latest Neoproterozoic.
  • Premisecitation

    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).”
    Quote in the paperNot a substantial claim1 of 3 sources checked
    • cites Gehling and Rigby, 1996 source
    • cites Brasier et al., 1997

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Chen et al., 2000 source

      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
  • Premisecitation

    Across Bilateria, cell type-specific gene expression in striated muscle cells is controlled by members of the MyoD family of bHLH transcriptional regulators and by regulators of the Mef2 class.

    “Across the Bilateria, for example, cell type-specific gene expression in striated muscle cells is controlled by members of the MyoD family of bHLH transcriptional regulators and by regulators of the Mef2 class (Molkentin et al., 1995) (reviewed by Zhang et al., 1999).”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites Molkentin et al., 1995 source
    • cites Zhang et al., 1999 source

      The Abstract and Results discuss Hairy, Groucho, and dCtBP in early Drosophila embryos, not regulation of striated-muscle gene expression across Bilateria. Searches for MyoD, Mef2, and muscle-specific regulators found no passage addressing the attributed claim. (LLM, conf=0.77)

      Experimental — accuracy not yet measured
  • Findingreasoning

    There is absence of evidence for macroscopic benthic adult bilaterian forms prior to 555 Mya.

    “More compelling is the absence of any evidence for macroscopic benthic adult bilaterian forms prior to 555 Mya.”
    Quote in the paperSubstantial claim
  • Premisecitation

    The oldest convincing bilaterian remains are Kimberella and various bilaterian trace fossils, dating only to about 555 Mya.

    “The oldest convincing remains of bilaterians are fossils of an already well-developed animal, Kimberella, which we discuss below, and of various bilaterian trace fossils.These date back only to about 555 Mya (Martin et al., 2000)”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Martin et al., 2000 source
  • May combine two claims. 33
  • Classified as probably not a substantial claim. 7
  • The quote only partly states this claim. 1

  • May combine two claims.

    Interpretationcitation

    What is actually homologous in the role of pax6 in diversely constructed eyes is only its function in controlling genes encoding visual pigments; the gene was later coopted for different morphogenetic programs.

    “The alternative is that what is actually homologous in the role of the pax6 gene in the diversely constructed eyes of various bilaterians is only its function in the control of genes encoding visual pigments.”
    Quote in the paperSubstantial claim1 of 3 sources checked
    • cites Sheng et al., 1997 source
    • cites Gehring and Ikeo, 1999 source
    • cites Davidson, 2001

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S1 (asserted), S4 (based).

    Premisereasoning

    These comparable deployment patterns have often been treated as evidence of functional homology, leading to the standard reconstruction of the PDA as a complex animal with some body parts like those of living bilaterians.

    “These similarities have been widely interpreted as functional homologies, producing the conventional view of the last common protostome-deuterostome ancestor (PDA) as a complex organism that possessed some of the same body parts as modern bilaterians.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Premisenone given

    A number of regulatory genes show broadly comparable deployment patterns in the formation of specific structures in flies and chordates.

    “Many regulatory genes appear to be utilized in at least superficially similar ways in the development of particular body parts in Drosophila and in chordates.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Further analyses of rDNA phylogeny, Hox gene sequences, and morphology place flatworms within lophotrochozoa and acoels within flatworms.

    “However, much further analysis of rDNA phylogeny as well as of Hox gene sequences and of morphological characters clearly places the flatworms within the lophotrochozoa, and the acoels within the flatworms (Adoutte, 2000;Berney et al., 2000;Littlewood et al., 2001;Peterson and Eernisse, 2001).”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Adoutte, 2000

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Berney et al., 2000 source
    • cites Littlewood et al., 2001 source

  • May combine two claims.

    Premisecitation

    Signal transduction pathways from ligands and receptors to transcription factors are orthologous and conserved across Bilateria.

    “the signal transduction pathways leading from intercellular ligands and cell surface receptors to transcription factors are orthologous, despite the variety of names, and are conserved across Bilateria.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Multiple major continental glaciations occurred between about 760 and 580 Mya, and at least one possibly involved sea-level glaciation at near-equatorial latitudes.

    “The latest Neoproterozoic is immediately preceded by multiple major continental glaciations that occurred between about 760 and 580 Mya (Kaufman et al., 1997).At least one and possibly more of these events involved glaciation at sea level at near-equatorial latitudes, a highly unusual occurrence.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Kaufman et al., 1997 source

  • May combine two claims.

    Premisecitation

    Differentiation, or cell-type specification, is due to expression of specific batteries of structural genes and is a property of individual cells.

    “Differentiation, or cell-type specification, is due to expression of specific batteries of structural genes that encode the proteins needed to endow that cell type with its functional properties; differentiation is a property of individual cells.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    Spatial control elements are like 'chips' that can build various patterning apparatuses; what they build depends on network architecture, not their identity.

    “We may think of these spatial control elements (and many others that could be mentioned) as 'chips' in the toolkit, that can be used to build a great variety of developmental patterning apparatuses.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Kimberella is interpreted as a benthic animal, most likely of protostome affinity and possibly a mollusk, with numerous specimens well dated at 555.3 Mya in northern Russia.

    “This is interpreted as a benthic animal, most likely of protostome affinity, and possibly a mollusk (Fedonkin and Waggoner, 1997).Numerous specimens of Kimberella have been well dated at 555.3 Mya in northern Russia (Martin et al., 2000).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Fedonkin and Waggoner, 1997 source
    • cites Martin et al., 2000 source

  • May combine two claims.

    Interpretationreasoning

    Because diverse crown-group bilaterians already existed in the Early Cambrian, bilaterian stem-group ancestors including the PDA must be significantly older than the Cambrian boundary and should predate Kimberella.

    “The most general argument, independent of molecular clock extrapolations, is that given the diversity of crown group bilaterians already present in the Early Cambrian, bilaterian stem group ancestors, including the PDA, must be significantly more ancient than the Cambrian boundary; and they should also predate Kimberella.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    If the protostome-deuterostome divergence occurred before these worldwide glaciations, the glaciations likely imposed a severe ecological constraint on the forms that could have survived.

    “Although the extent of glaciation remains uncertain, if the protostome-deuterostome divergence occurred before these world-wide glaciations, they are likely to have imposed a severe ecological constraint on the forms that could have survived.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    Primary differentiated cell types occur in all bilaterians, so the genome of the PDA must have included the respective differentiation gene batteries and their controllers.

    “Primary differentiated cell types such as muscle cells, neurons of various sorts, photosensitive cells, etc., occur in all bilaterians and it follows that the genome of the PDA must have included the respective differentiation gene batteries and their controllers.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisenone given

    The first appearance and diversification of crown-group bilaterian clades occurred during the Early Cambrian.

    “The first appearance and diversification of crown group bilaterian clades occurs during the Early Cambrian.”
    Quote in the paperNot a substantial claim

  • May combine two claims. The quote only partly states this claim.

    Interpretationreasoning

    If the last common PDA predates 555 Mya, it is very unlikely to have been constructed in a complex manner, or its remains would probably have been found.

    “One constraint is that if the last common PDA predates 555 Mya it is very unlikely to have been constructed in a complex manner”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The Neoproterozoic fossil record has been sampled well enough that a complex PDA would likely have been detected if it existed.

  • May combine two claims.

    Interpretationreasoning

    The revised topology has fundamentally changed inferred morphological homologies among Bilateria and interpretations of conserved developmental programs.

    “The revised topology of Fig. 1B has fundamentally altered inferred morphological homologies among the Bilateria, and in consequence has affected interpretations of conserved developmental programs.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    A variety of bilaterian differentiation gene batteries are shared with cnidarians, while others are bilaterian-only.

    “In summary, we conclude that a variety of bilaterian differentiation gene batteries are also shared with cnidarians, while others occur only among bilaterians.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    In development, morphogenetic regulatory programs for pattern formation precede cell differentiation programs, but the reverse is likely to have been true in the evolution of body parts.

    “In development, morphogenetic regulatory programs for pattern formation precede the institution of cell differentiation programs, but it is likely to have been the reverse in the evolution of body parts.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    The Neoproterozoic fossil record does not yet explicitly illuminate the PDA and its antecedents, but it leaves valuable limits.

    “So, in summary, although the Neoproterozoic fossil record does not yet explicitly illuminate the PDA and its antecedents, it leaves us with some valuable limits.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationcitation

    The bottom-up view holds that controlling differentiation gene batteries was primitive for each body part, while morphogenetic programs are not conserved but evolved independently and were added later.

    “The 'bottom-up' view of body part evolution considered here (Davidson, 2001) is one in which the function of controlling differentiation gene batteries was primitive for each body part, while the morphogenetic programs are not conserved, but instead evolved independently and were added in later.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Davidson, 2001

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Interpretationreasoning

    The PDA had an AP axis, two-ended gut, mesodermal layers, and central/peripheral nervous system with sensory cells.

    “It had an AP axis, a twoended gut, mesodermal layers and a central and peripheral nervous system with sensory cell types.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The PDA had all the general features discussed: a two-ended gut, mesodermal layers and structures, and a central nervous system.

  • May combine two claims.

    Interpretationreasoning

    The most reasonable conclusion is that the Neoproterozoic PDA was small and probably constructed simply and delicately.

    “The most reasonable conclusion is that the Neoproterozoic PDA must have been small and was probably constructed simply and delicately.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S1 (asserted), S3 (load-bearing).

    Premisecitation

    Runnegar argued that conditions even within glacial refugia would have allowed survival only of small, simply constructed, pelagic bilaterian stem-group forms.

    “Runnegar (Runnegar, 2000) argued that conditions even within the refugia would have allowed survival only of small, simply constructed, pelagic bilaterian stem group forms”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Runnegar, 2000

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Premisecitation

    Molecular phylogenetics reveals metazoan relationships very different from traditional topologies, including placement of acoelomates and pseudocoelomates within protostomes, recognition of ecdysozoa and lophotrochozoa, and alliance of annelids with molluscs rather than arthropods.

    “Among the most important changes are the transfer of the acoelomates and pseudocoelomates to within the protostomes; the recognition of two great protostome subclades, the ecdysozoa and lophotrochozoa, and the alliance of annelids with molluscs and other lophotrochozoans rather than with arthropods (ecdysozoa).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisenone given

    The Ediacaran fauna appears in the latest Neoproterozoic (c. 575-543 Mya), with a few forms extending into the earliest Cambrian, and includes at least one demonstrable adult bilaterian, Kimberella.

    “A new assemblage of organisms, known as Ediacaran fauna, appears in the latest Neoproterozoic (c 575-543 Mya), with a few extending into the earliest Cambrian.”
    • Also stated in: § THE 'MISSING' FOSSIL RECORD · boosted
      “at least one demonstrable adult bilaterian form, Kimberella (Fig. 2).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S2 (checkable).

    Interpretationreasoning

    It is dangerous to assume such chips have a hard pan-bilaterian morphogenetic assignment conserved from an ancestral form.

    “Therefore it is particularly dangerous to assume that such chips have a hard, pan-bilaterian morphogenetic assignment, that has been conserved from an ancestral form.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    When bilaterian traces appear, they indicate animals with anteroposterior differentiation, but there is no evidence of limbs.

    “When they do appear, these bilaterian traces indicate the presence of animals that had AP differentiation, but there is no evidence of limbs.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisenone given

    After 550 Mya metazoan diversity and complexity accelerated, beginning with simple skeletonized tubes and more complex trace fossils, followed at about 530 Mya by the first brachiopods, molluscs, and arthropods.

    “After 550 Mya there is an accelerating increase in metazoan diversity and complexity, beginning with simple skeletonized tubes and more complex trace fossils, followed at about 530 Mya by the first brachiopods, molluscs and arthropods.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    The absence of bilaterian fossils before the very end of the Neoproterozoic does not prove that bilaterians were absent then, but it does place meaningful constraints on what they could have been like.

    “The absence of bilaterian fossils prior to the very end of the Neoproterozoic, at least so far, does not mean that bilaterians did not exist then, but it does place meaningful constraints on their possible nature.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The Neoproterozoic fossil record has been sampled well enough that a complex PDA would likely have been detected if it existed.

  • May combine two claims.

    Interpretationcitation

    Phosphatic preservation like that in the Doushantuo appears restricted to a relatively narrow Neoproterozoic interval, and similar preservation opportunities may not occur in older rocks.

    “Such unusual phosphatic preservation has been described from elsewhere in the Phanerozoic, but this complex preservational environment (Xiao and Knoll, 1999) appears restricted to a relatively narrow interval of the Neoproterozoic (Cook and Shergold, 1984).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Xiao and Knoll, 1999 source
    • cites Cook and Shergold, 1984 source

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing), S4 (based). May combine two claims.

    Interpretationreasoning

    Fossilization of this simple PDA might require rare special circumstances, and its fossils might not be recognized as such unless prior expectations are adjusted.

    “Fossilization of this animal might require rare special circumstances, and unless prior expectations are suitably adjusted, its fossils might not be recognized as such even if found.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S1 (asserted).

    Interpretationreasoning

    If the canonical body parts of all bilaterians are truly homologous, then the PDA should have had all these same parts.

    “If the canonical body parts of all bilaterians are truly homologous, as suggested by commonalties in their developmental regulatory programs, then the PDA should have had all these same parts.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationnone given

    Other Ediacaran fossils assigned to annelids, echinoderms, or arthropods lack characters convincingly supporting those assignments; most lack appendages, mouth, digestive system, or other bilaterian characters and can be interpreted as cnidarian-grade.

    “Other elements of the Ediacaran fauna have been assigned to the annelids, echinoderms and arthropods, but none display characters convincingly supporting such phylogenetic assignments.Most Ediacaran fossils lack clearly identifiable appendages, mouth, indications of a digestive system or other characters supporting assignment to the Bilateria.But most can be comfortably interpreted as cnidarian-”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    In each body part, the same differentiated cell types are employed across Bilateria, and this fact underlies their analogous functions.

    “However, in each of the body parts, respectively, the same differentiated cell types are employed across the Bilateria, and it is this fact that underlies their analogous functions”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    The PDA possessed the essential bilaterian toolkit and deployed many differentiation gene batteries.

    “In conclusion, the PDA possessed the essential bilaterian toolkit for morphogenetic pattern formation, and it deployed many of the differentiation gene batteries that its modern descendants continue to rely on.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationcitation

    There is already some convincing evidence that the architecture of gene networks controlling formation of many analogous body parts in unrelated bilaterian clades is clade-specific, while the regulatory apparatus for differentiated cell types is conserved across Bilateria.

    “Though yet fragmentary, there is already some convincing evidence on both scores (Davidson, 2001).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Davidson, 2001

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

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

    Premisecitation

    Many new acritarch groups appeared during the earliest Cambrian, perhaps linked to the origin of zooplankton.

    “Many new acritarch groups appeared during the earliest Cambrian (Vidal and Moczydl ⁄ owska-Vidal, 1997), perhaps linked to the origination of zooplankton (Butterfield, 1997).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Vidal and Moczydl ⁄ owska-Vidal, 1997 source
    • cites Butterfield, 1997 source

  • May combine two claims.

    Premisecitation

    Acritarchs are the most diverse and heterogeneous fossils from the 1200-740 Mya interval and increased greatly in diversity during the Neoproterozoic.

    “The most diverse and heterogeneous fossils from this interval are resistant, organic-walled microfossils known as acritarchs, which increased greatly in diversity during the Neoproterozoic (Knoll, 1996; Vidal and Moczydl ⁄ owska-Vidal, 1997; Xiao and Knoll, 1999; Zhou et al., 2001).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Knoll, 1996

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Vidal and Moczydl ⁄ owska-Vidal, 1997 source
    • cites Xiao and Knoll, 1999 source

  • May combine two claims.

    Premisecitation

    Many conserved developmental control genes and some differentiated cell types are present in Cnidaria.

    “Many of the highly conserved developmental control genes are also present in Cnidaria, as are some of these same differentiated cell types”
    Quote in the paperSubstantial claim
38 of 38

  • The authors state this as an assumption.

    Drosophila and vertebrates are adequate surrogates for Bilateria in comparative analysis of conserved regulatory systems.

    “Taking Drosophila and vertebrates as surrogates for Bilateria (this leaves aside Lophotrochozoa, for which there is as yet only relatively sparse molecular biological evidence)”

  • The paper relies on this without support.

    The Neoproterozoic fossil record has been sampled well enough that a complex PDA would likely have been detected if it existed.

    “Paleontologists have extensively explored vast areas of the Neoproterozoic (1000-543 Mya) fossil record, including a variety of marine environments and styles of preservation.”

  • The paper relies on this without support.

    Molecular clock estimates, despite potential problems, are reliable enough to indicate that the latest PDA is much older than the latest Neoproterozoic.

    “Despite various potential problems with molecular clock estimates (Smith and Peterson, 2002), most of these suggest that the age of the latest PDA must lie much deeper in time than the latest Neoproterozoic.”

  • The paper relies on this without support.

    The absence of trace fossils of burrowing by animals about 1 cm or longer before 575/543 Mya reflects absence of such animals rather than preservation bias.

    “The lack of any evidence of horizontal burrowing in rocks older than about 575 Mya and of vertical burrowing in rocks older than 543 Mya is a strong argument that there existed no animals about 1 cm or longer that were capable of disturbing sedimentary layers before this time.”

  • The authors state this as an assumption.

    The PDA had all the general features discussed: a two-ended gut, mesodermal layers and structures, and a central nervous system.

    “We may assume that the PDA had all these general features, and that it utilized some of the genetic control apparatus which modern Bilateria display in the development of these basal aspects of their body plans.”

  • The authors state this as an assumption.

    The PDA utilized some of the genetic control apparatus that modern Bilateria display in developing these basal body plan features.

    “We may assume that the PDA had all these general features, and that it utilized some of the genetic control apparatus which modern Bilateria display in the development of these basal aspects of their body plans.”

  • The authors state this as an assumption.

    The PDA's morphology was unprepossessing.

    “the safest assumption is that its morphology was unprepossessing.”
7 of 7

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?

  • At least 600 million years of evolution separate cnidarians from bilaterians.

    “Though at least 600 million years of evolution separate cnidarians from bilaterians [9–16], many aspects of the nervous system are conserved, including neuropeptides and neurotransmitters [15–20].”

    From The Jellyfish Cassiopea Exhibits a Sleep-like State (2017) · cites this paper as [12]

  • Bilaterians employ similar fundamental approaches in constructing their varied body forms.

    “Over the last decade, an enormous amount of evidence from developmental molecular biology, much of it presented in these same pages, has shown that all Bilateria share a common genetic toolkit for development, and that all Bilateria use the same basic strategies to build their diverse body plans (reviewed in Davidson, 2001;Erwin and Davidson, 2002;Carroll et al., 2001).”

    From Precambrian Animal Life: Probable Developmental and Adult Cnidarian Forms from Southwest China (2002) · cites this paper as Erwin and Davidson, 2002

  • Bilaterians possess a shared set of developmental genes.

    “Over the last decade, an enormous amount of evidence from developmental molecular biology, much of it presented in these same pages, has shown that all Bilateria share a common genetic toolkit for development, and that all Bilateria use the same basic strategies to build their diverse body plans (reviewed in Davidson, 2001;Erwin and Davidson, 2002;Carroll et al., 2001).”

    From Precambrian Animal Life: Probable Developmental and Adult Cnidarian Forms from Southwest China (2002) · cites this paper as Erwin and Davidson, 2002

  • Fossil evidence is nearly absent regarding the shape, age, or stem lineage of the last common bilaterian ancestor.

    “But of the form of this ancestor, or the time at which it lived, or the nature of the stem group lineage from which it derived, there is yet almost no information in the fossil record (see Erwin and Davidson, 2002 for discussion).”

    From Precambrian Animal Life: Probable Developmental and Adult Cnidarian Forms from Southwest China (2002) · cites this paper as Erwin and Davidson, 2002

  • These results suggest that the biochemical functions of CnASH have been conserved despite the divergence of cnidarians and arthropods before the Cambrian explosion.

    “These results suggest that although cnidarians and arthropods diverged prior to the Cambrian explosion (Erwin and Davidson, 2002), the biochemical functions of the CnASH protein have been conserved”

    From Evolutionary aspects of developmentally regulated helix-loop-helix transcription factors in striated muscle of jellyfish (2003) · cites this paper as Erwin and Davidson, 2002

Cites

Flagged first, then by citations

3 of the 153 references couldn’t be matched to a known paper.

Research works printed but not linked: 7

  1. Chen, J. Y. and Zhou, G. (1997). Biology of the Chengjian fauna. In The Cambrian Explosion and the Fossil Record (ed. J. Y. Chen, Y.-n. Cheng and H. V. Iten). Bulletin of the National Museum of Natural Science 10, pp. 11-116, Taiwan, China.
  2. Clark, R. B. (1979). Radiation of the Metazoan. In The Origin of Major Invertebrate Groups (ed. M. R. House), pp. 55-101. Academic Press: London.
  3. Crimes, T. P. (1994). The period of early evolutionary failure and the dawn of evolutionary success: the record of biotic changes across the Precambrian-Cambrian boundary. In The Palaeobiology of Trace Fossils (ed. S. K. Donovan), pp. 105-133. London: J. Wiley & Sons.
  4. Knoll, A. H. (1996). Archean and Proterozoic paleontology. In Palynology: Principles and applications, vol. 1 (ed. J. Jansonius and D. C. McGregor), pp. 51-80. American Association of Palynologists Foundation.
  5. Platt, H. M. (1980). Meiofaunal dynamics and the origin of the metazoa. In The Evolving Biosphere (ed. P. L. Forey), pp. 207-216. Cambridge, UK: Cambridge University Press.
  6. Tanaka, M., Kasahara, H., Bartunkova, S., Schinke, M., Komuro, I., Inagaki, H., Lee, Y., Lyons, G. E. and Izumo, S. (1998). Vertebrate homologs of tinman and bagpipe: Roles of the homeobox genes in cardiovascular development. Dev. Genet. 22, 239-249. · DOI
  7. Walossek, D. and Müller, K. J. (1994). Pertastomid parasites from the Lower Paleozoic of Sweden. Trans. R. Soc. Edinburgh85, 1-37.

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Related

Authors
Erwin, D. H., & Davidson, E. H.
Affiliations
  • National Museum of Natural History (US)
  • California Institute of Technology (US)
ORCID
Erwin, Douglas H.
Venue
Development
Publisher
The Company of Biologists
Published
2002-07-01
Volume
129
Issue
13
Pages
3021-3032
ISSN
  • 0950-1991 (ISSN-L)
  • 1477-9129
DOI
10.1242/dev.129.13.3021
OpenAlex
W2165511961
Cited by
320
References
153
Citations by year
2026: 3 · 2025: 3 · 2024: 13 · 2023: 7 · 2022: 8 · 2021: 6 · 2020: 4 · 2019: 13 · 2018: 9 · 2017: 7 · 2016: 4 · 2015: 15 · 2014: 10 · 2013: 9 · 2012: 10
FWCI
1.42
Type
journal article
Language
en
Open access
Locations
  • Development (publishedVersion)
  • PubMed (publishedVersion)
  • CaltechAUTHORS (California Institute of Technology) (submittedVersion)
  • HighWire Press Open Archive (submittedVersion)
Funders
  • Eugene V. and Claire E. Thaw Charitable Trust
  • Santa Fe Institute
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Developmental Biology and Gene Regulation
  • Physical Sciences › Earth and Planetary Sciences › Paleontology › Marine Invertebrate Physiology and Ecology
  • Social Sciences › Arts and Humanities › History and Philosophy of Science › Philosophy and History of Science
Keywords
bilaterian evolution, regulatory genes, functional homology, Drosophila, Chordata, body plan, evolutionary developmental biology
MeSH terms
Animals, Chordata, Nonvertebrate, Drosophila, Biological Evolution, Fossils, Morphogenesis, Phylogeny, Gene Expression Regulation, Developmental

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.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-09-30.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-09-30.

Cited sources are checked by gpt-6-sol.

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.

What counts as a claim ›How we measure confidence ›How we check this ›

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