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Cited by 113Marine Invertebrate Physiology and EcologyDevelopmental Biology and Gene RegulationPlanarian Biology and Electrostimulation

Gastric pouches and the mucociliary sole: setting the stage for nervous system evolution

Open access
Arendt, Detlev, Benito-Gutierrez, Elia, Brunet, Thibaut, Marlow, Heather·2015·Philosophical Transactions of the Royal Society B: Biological Sciences
DOI 10.1098/rstb.2015.0286PMC PMC4650134
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Abstract

Prerequisite for tracing nervous system evolution is understanding of the body plan, feeding behaviour and locomotion of the first animals in which neurons evolved. Here, a comprehensive scenario is presented for the diversification of cell types in early metazoans, which enhanced feeding efficiency and led to the emergence of larger animals that were able to move. Starting from cup-shaped, gastraea-like animals with outer and inner choanoflagellate-like cells, two major innovations are discussed that set the stage for nervous system evolution. First, the invention of a mucociliary sole entailed a switch from intra- to extracellular digestion and increased the concentration of nutrients flowing into the gastric cavity. In these animals, an initial nerve net may have evolved via division of labour from mechanosensory-contractile cells in the lateral body wall, enabling coordinated movement of the growing body that involved both mucociliary creeping and changes of body shape. Second, the inner surface of the animals folded into metameric series of gastric pouches, which optimized nutrient resorption and allowed larger body sizes. The concomitant acquisition of bilateral symmetry may have allowed more directed locomotion and, with more demanding coordinative tasks, triggered the evolution of specialized nervous subsystems. Animals of this organizational state would have resembled Ediacarian fossils such as Dickinsonia and may have been close to the cnidarian–bilaterian ancestor. In the bilaterian lineage, the mucociliary sole was used mostly for creeping, or frequently lost. One possible remnant is the enigmatic Reissner's fibre in the ventral neural tube of cephalochordates and vertebrates.

Verified 2026-10-06 · 3 references not checked yet

AI snapshot

Written from the paper’s full text.

TL;DR

This review proposes a cell-type–based scenario for early metazoan evolution in which a mucociliary sole for external digestion and metameric gastric pouches set the stage for nervous system evolution. It argues that the first nerve net arose by division of labour from mechanosensory-contractile ectochoanocytes, and that animals of this grade resembled Ediacaran *Dickinsonia* and were close to the cnidarian–bilaterian ancestor.

Key findings

  • Two major innovations are proposed as prerequisites for nervous system evolution: a mucociliary sole, which switched feeding from intra- to extracellular digestion and increased nutrient concentration in the gastric cavity, and metameric gastric pouches, which expanded resorptive surface and allowed larger body sizes.
  • The first nerve net is hypothesized to have evolved by division of labour from mechanosensory-contractile cells in the lateral body wall, enabling coordinated movement involving mucociliary creeping and body-shape changes; glutamate is proposed as the first excitatory transmitter and GABA as inhibitory.
  • Gastric pouches are proposed as homologous to bilaterian coelomic cavities, supported by *gbx* expression in all but the first pair of pouches in sea anemone and amphioxus, staggered/collinear *hox* expression, and expression of somitic musculature genes such as *mox* and *twist*.
  • The organizational grade is compared to Ediacaran *Dickinsonia*, with its metameric digestive diverticula, and placed close to the cnidarian–bilaterian ancestor; Reissner’s fibre in cephalochordates and vertebrates is suggested as a possible remnant of the mucociliary sole.

Methods

  • This is a review and synthetic evolutionary scenario, not a primary data paper; it integrates comparative structural and ultrastructural data, molecular studies on basal metazoans and choanoflagellates, developmental biology, and palaeontology.
  • The main analytical framework is cell-type diversification via the sister cell-type concept and division of labour, used to infer ancestral cell types such as ectochoanocytes, endochoanocytes, kopeocytes, mucocytes, zymocytes, enterocytes, and nerve net neurons.
  • Homology arguments draw on gene expression data, including *gbx*, *hox*, *mox*, *twist*, *foxj*, *foxA*, *atonal*, and *achaete-scute* family genes, alongside fossil comparisons such as *Dickinsonia*.

Limitations

  • The paper states that in the absence of comparative molecular data for most cell types discussed, the postulated sequence of cell-type diversification remains tentative.
  • The paper notes that the early metazoan tree remains unsolved, the placement of ctenophores is uncertain, and the existence of a “Neuralia” grouping excluding sponges and placozoans remains unsettled.
  • The paper states it cannot explain why Reissner’s fibre is so persistent in extant vertebrates; more broadly, the text makes evident that many proposed cell types and transitions are hypothetical and not yet directly tested by comparative single-cell profiling.

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

Integrity signals

Registry

Crossref · 10.1098/rstb.2015.0286

Cites

172 of 175 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 125 cited sources checked · 0 supported · 0 flagged

  • Interpretationreasoning

    An initial nerve net may have evolved via division of labour from mechanosensory-contractile cells in the lateral body wall, enabling coordinated movement involving both mucociliary creeping and changes of body shape.

    “In these animals, an initial nerve net may have evolved via division of labour from mechanosensory-contractile cells in the lateral body wall, enabling coordinated movement of the growing body that involved both mucociliary creeping and changes of body shape.”
    Quote in the paperNot a substantial claim
  • Interpretationcitation

    Early metazoan cells formed lamellipodia and filopodia, using proteins that reorganize cortical actin filaments such as the Arp2/3 complex, fascin, and myosin X.

    “In addition, we can infer that early metazoan cells formed lamellipodia and filopodia, using proteins that reorganize cortical actin filaments such as the Arp2/3 complex, the actin cross-linking protein fascin, and myosin X”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [39] Sebe-Pedros A, Burkhardt P, Sanchez-Pons N, Fairclough SR, Lang BF, King N, Ruiz-Trillo I 2013 Insights into the origin of metazoan filopodia and microvilli. Mol. Biol. Evol. 30, 2013– 2023. (10.1093/molbev/mst110) 23770652 PMC3748353 source

      Not checked in the free run.

    • cites [40] Jekely G 2014 Origin and evolution of the self-organizing cytoskeleton in the network of eukaryotic organelles. Cold Spring Harb. Perspect. Biol. 6, a016030 (10.1101/cshperspect.a016030) 25183829 PMC4142967 source

      Not checked in the free run.

  • Interpretationcitation

    Such equipped animals may have been close to some simple Ediacaran fossils that have been interpreted as grazing on algal mats with a mucociliary sole for external digestion.

    “Such equipped animals may have been close to some simple Ediacaran fossils that have been interpreted as grazing on algal mats with a mucociliary sole for external digestion [3].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [3] Sperling EA, Vinther J 2010 A placozoan affinity for Dickinsonia and the evolution of Late Proterozoic metazoan feeding modes. Evol. Dev. 12, 201– 209. (10.1111/j.1525-142X.2010.00404.x) 20433459 source

      Not checked in the free run.

  • Interpretationreasoning

    Many of these molecules and associated functions were key to the evolution of the first neural cell types.

    “Many of these molecules and associated functions were key to the evolution of the first neural cell types, as will be detailed below.”
    Quote in the paperSubstantial claim
  • Interpretationcitation

    Stem metazoans were likely composed of one main characteristic cell type, resembling, structurally and functionally, the choanoflagellates.

    “Stem metazoans were likely composed of one main characteristic cell type, resembling, structurally and functionally, the choanoflagellates [8–10; see however 11].”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [8] Nielsen C 2008 Six major steps in animal evolution: are we derived sponge larvae? Evol. Dev. 10, 241– 257. (10.1111/j.1525-142X.2008.00231.x) 18315817 source

      Not checked in the free run.

    • cites [9] Haeckel E 1874 Die Gastraea-Theorie, die phylogenetische Classification des Thierreiches und die Homologie der Keimblätter. Jena Z. Naturwiss. 8, 1– 55.

      Not checked in the free run.

    • cites [10] Maldonado M 2004 Choanoflagellates, choanocytes, and animal multicellularity. Invertebr. Biol. 123, 1– 22. (10.1111/j.1744-7410.2004.tb00138.x) source

      Not checked in the free run.

  • May combine two claims. 41
  • Classified as probably not a substantial claim. 25

  • May combine two claims.

    Interpretationreasoning

    Animals of this organizational state would have resembled Ediacarian fossils such as Dickinsonia and may have been close to the cnidarian-bilaterian ancestor.

    “Animals of this organizational state would have resembled Ediacarian fossils such as Dickinsonia and may have been close to the cnidarian–bilaterian”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    The concomitant acquisition of bilateral symmetry may have allowed more directed locomotion and, with more demanding coordinative tasks, triggered the evolution of specialized nervous subsystems.

    “The concomitant acquisition of bilateral symmetry may have allowed more directed locomotion and, with more demanding coordinative tasks, triggered the evolution of specialized nervous subsystems.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationnone given

    The inner surface of the animals folded into metameric series of gastric pouches, which optimized nutrient resorption and allowed larger body sizes.

    “Second, the inner surface of the animals folded into metameric series of gastric pouches, which optimized nutrient resorption and allowed larger body sizes.”
    Quote in the paperNot a substantial claim

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

    Interpretationnone given

    In the bilaterian lineage, the mucociliary sole was used mostly for creeping, or frequently lost.

    “In the bilaterian lineage, the mucociliary sole was used mostly for creeping, or frequently lost.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S2 (checkable), S4 (based).

    Premisenone given

    Understanding the body plan, feeding behaviour and locomotion of the first animals in which neurons evolved is a prerequisite for tracing nervous system evolution.

    “Prerequisite for tracing nervous system evolution is understanding of the body plan, feeding behaviour and locomotion of the first animals in which neurons evolved.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based). May combine two claims.

    Interpretationnone given

    The invention of a mucociliary sole entailed a switch from intra- to extracellular digestion and increased the concentration of nutrients flowing into the gastric cavity.

    “First, the invention of a mucociliary sole entailed a switch from intra- to extracellular digestion and increased the concentration of nutrients flowing into the gastric cavity.”
    Quote in the paperNot a substantial claim

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

    Interpretationnone given

    One possible remnant of the mucociliary sole is the enigmatic Reissner's fibre in the ventral neural tube of cephalochordates and vertebrates.

    “One possible remnant is the enigmatic Reissner's fibre in the ventral neural tube of cephalochordates and vertebrates.”
    Quote in the paperNot a substantial claim

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

    Interpretationnone given

    The first animals in which neurons evolved started from cup-shaped, gastraea-like animals with outer and inner choanoflagellate-like cells.

    “Starting from cup-shaped, gastraea-like animals with outer and inner choanoflagellate-like cells, two major innovations are discussed that set the stage for nervous system evolution.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationcitation

    The slow myosin is also involved in amoeboid movement, which probably belonged to the behavioural repertoire of early metazoan cells.

    “The slow myosin is also involved in amoeboid movement [38], which probably belonged to the behavioural repertoire of early metazoan cells.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [38] Liu YJ, Le Berre M, Lautenschlaeger F, Maiuri P, Callan-Jones A, Heuze M, Takaki T, Voituriez R, Piel M 2015 Confinement and low adhesion induce fast amoeboid migration of slow mesenchymal cells. Cell 160, 659– 672. (10.1016/j.cell.2015.01.007) 25679760

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The flagellar cilia were both motile and sensory, and thus contained a very short and direct sensory-effector arc.

    “The flagellar cilia were both motile and sensory (as reported for unicellular eukaryotes and human airway cilia), and thus contained a very short and direct sensory-effector arc [22].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [22] Salathe M 2007 Regulation of mammalian ciliary beating. Annu. Rev. Physiol. 69, 401– 422. (10.1146/annurev.physiol.69.040705.141253) 16945069

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    These ancestors represented an epithelium that took the shape of a sphere, called choanoblastaea, which later gave rise to the cup-shaped gastraea.

    “These ancestors represented an epithelium [14] that took the shape of a sphere, called choanoblastaea [8], which later gave rise to the cup-shaped gastraea”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [8] Nielsen C 2008 Six major steps in animal evolution: are we derived sponge larvae? Evol. Dev. 10, 241– 257. (10.1111/j.1525-142X.2008.00231.x) 18315817 source

      Not checked in the free run.

    • cites [14] Leys SP, Riesgo A 2012 Epithelia, an evolutionary novelty of metazoans. J. Exp. Zool. B Mol. Dev. Evol. 318, 438– 447. (10.1002/jez.b.21442) 22057924

      Not checked in the free run.

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

    Interpretationnone given

    The extensive folding of the inner surface into metameric pouches optimized nutrient distribution and resorption.

    “the extensive folding of the inner surface into metameric pouches, which optimized nutrient distribution and resorption”
    Quote in the paperNot a substantial claim

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

    Interpretationreasoning

    Endochoanocytes diversified into cell types specializing in internal nutrient distribution and resorption.

    “the endochoanocytes into cell types specializing in internal nutrient distribution and resorption”
    Quote in the paperNot a substantial claim

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

    Interpretationreasoning

    Ectochoanocytes diversified into cell types specializing in mechanosensation, information integration and body contractions in response to environmental stimuli.

    “and the ectochoanocytes into cell types specializing in mechanosensation, information integration and body contractions in response to environmental stimuli”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given

    The division of labour accompanied the birth of the first neurons and muscle cells.

    “One prominent example is the division of labour that accompanied the birth of the first neurons and muscle cells (see §2).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    A new feeding mode, mucoid-ciliary particle feeding, evolved in the Precambrian ocean and early metazoans.

    “Various lines of evidence indicate that a new feeding mode evolved in the Precambrian ocean, referred to as mucoid-ciliary particle feeding [3] (figure 4a,b).”
    • Also stated in: § Grazing algal mats with mucus and digestive gland cells · hedged
      “A rich body of fossil and comparative evidence indicates that mucoid-ciliary particle feeding evolved in early metazoans.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [3] Sperling EA, Vinther J 2010 A placozoan affinity for Dickinsonia and the evolution of Late Proterozoic metazoan feeding modes. Evol. Dev. 12, 201– 209. (10.1111/j.1525-142X.2010.00404.x) 20433459 source

      Not checked in the free run.

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

    Interpretationreasoning

    The simple, bilayered, cup-shaped anatomy of the gastraea was reflected by a first diversification at the cellular level into ectochoanocytes, endochoanocytes, and kopeocytes.

    “We will hypothesize that the simple, bilayered, cup-shaped anatomy of this ancestor was reflected by a first diversification at the cellular level, including: (i) the external ‘ectochoanocytes’, mediating interactions with the environment; (ii) the internal ‘endochoanocytes’ that specialized towards particle capture and nutrient resorption; and (iii) the ‘kopeocytes’, regulating water currents”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Choanoflagellates and metazoans share synaptic adhesion/signalling molecules, a primordial neurosecretory apparatus active on the apical cell surface (but no presynaptic active zone proteins), postsynaptic density proteins such as Homer or Shank, and a variety of receptors including the metabotropic glutamate receptor (but not ionotropic glutamate receptors).

    “choanoflagellates and metazoans share synaptic adhesion/signalling molecules, a primordial neurosecretory apparatus active on the apical cell surface (but no presynaptic active zone proteins) [32], postsynaptic density proteins such as Homer or Shank [33,34] and a variety of receptors including the metabotropic glutamate receptor [35] (but not ionotropic glutamate receptors, which only appeared in”
    Quote in the paperSubstantial claim0 of 4 sources checked
    • cites [32] Burkhardt P 2015 The origin and evolution of synaptic proteins—choanoflagellates lead the way. J. Exp. Biol. 218, 506– 514. (10.1242/jeb.110247) 25696814 source

      Not checked in the free run.

    • cites [33] Alie A, Manuel M 2010 The backbone of the post-synaptic density originated in a unicellular ancestor of choanoflagellates and metazoans. BMC Evol. Biol. 10, 34 (10.1186/1471-2148-10-34) 20128896 PMC2824662

      Not checked in the free run.

    • cites [34] Ryan TJ, Grant SG 2009 The origin and evolution of synapses. Nat. Rev. Neurosci. 10, 701– 712. (10.1038/nrn2717) 19738623

      Not checked in the free run.

    • cites [35] Krishnan A, Schioth HB 2015 The role of G protein-coupled receptors in the early evolution of neurotransmission and the nervous system. J. Exp. Biol. 218, 562– 571. (10.1242/jeb.110312) 25696819 source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    With these changes, basal metazoans had reached the organizational grade of the Ediacaran fossil Dickinsonia, which may have been close to the last common ancestor of cnidarians and bilaterians ('Metameria').

    “We propose that, with these changes, basal metazoans had reached the organizational grade of the Ediacaran fossil Dickinsonia, which may have been close to the last common ancestor of cnidarians and bilaterians (that we collectively refer to as ‘Metameria’, figure 1a).”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    Cell-type diversification involves the segregation and divergence of existing cellular modules or functions.

    “Cell-type diversification involves the segregation and divergence of existing cellular modules or functions [5].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [5] Arendt D 2008 The evolution of cell types in animals: emerging principles from molecular studies. Nature reviews. Genetics 9, 868– 882. (10.1038/nrg2416) 18927580

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S4 (based). May combine two claims.

    Interpretationnone given

    Sponges might be regarded as representatives of a gastraea-type organization, which then would have undergone surface extension independent of other metazoan lineages.

    “Sponges might be regarded as representatives of a gastraea-type organization (which then would have undergone surface extension independent of other metazoan lineages”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    In mucoid-ciliary particle feeding, food was predigested externally in a mucus layer and the predigested nutrients were transported into the body cavity with water currents.

    “Food was predigested externally in a layer of mucus and the predigested nutrients transported into the body cavity with water currents.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    The most characteristic feature of the gastraea is the infolding of the lower body surface, resulting in an outer ectoderm, an inner gastroderm and a gastric opening.

    “Its most characteristic feature is the infolding of the lower body surface, resulting in an outer ectoderm, an inner gastroderm and a gastric opening (figure 3a).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [9] Haeckel E 1874 Die Gastraea-Theorie, die phylogenetische Classification des Thierreiches und die Homologie der Keimblätter. Jena Z. Naturwiss. 8, 1– 55.

      Not checked in the free run.

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

    Premisecitation

    The first metazoan cells had an apical collar with an undulating flagellum.

    “classical authors agreed that the first metazoan cells had an apical collar with an undulating flagellum [16,17]”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [16] Hibberd DJ 1975 Observations on the ultrastructure of the choanoflagellate Codosiga botrytis (Ehr.) Saville-Kent with special reference to the flagellar apparatus. J. Cell Sci. 17, 191– 219. 1089676

      Not checked in the free run.

    • cites [17] Leadbeater BSC 1983 Distribution and chemistry of microfilaments in choanoflagellates, with special reference to the collar and other tentacle systems. Protistologia 10, 157– 166.

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    Digestive enzymes were secreted into the mucus layer for external digestion, and coordinated ciliary beating transported the mucus over the digestive epithelium and washed nutrients into the gastric cavity.

    “Digestive enzymes were secreted into this mucus layer for external digestion. The coordinated and directional beating of effective stroke cilia distributed and transported the mucus over the digestive epithelium and washed the nutrients into the gastric cavity.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Interpretationcitation

    The transformation of the spherical blastaea into the gastraea was the second step in the evolution of the metazoan body, and the gastraea may have been close to the last metazoan common ancestor.

    “It is a long-standing notion that the second step in the evolution of the metazoan body was the transformation of the spherical blastaea into the gastraea [8,9], which may have been close to the last metazoan common ancestor (figure 1b).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [8] Nielsen C 2008 Six major steps in animal evolution: are we derived sponge larvae? Evol. Dev. 10, 241– 257. (10.1111/j.1525-142X.2008.00231.x) 18315817 source

      Not checked in the free run.

    • cites [9] Haeckel E 1874 Die Gastraea-Theorie, die phylogenetische Classification des Thierreiches und die Homologie der Keimblätter. Jena Z. Naturwiss. 8, 1– 55.

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Even in sponges, a transitory cup-like stage forms during metamorphosis; and in cnidarians and ctenophores, the overall body form resembles that of a gastrula during the entire life cycle.

    “Even in sponges, a transitory cup-like stage forms during metamorphosis, as recently confirmed [41]; and in cnidarians and ctenophores, the overall body form resembles that of a gastrula during the entire life cycle—at larval, polyp and medusa stages.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [41] Leys SP, Eerkes-Medrano D 2005 Gastrulation in calcareous sponges: in search of Haeckel's gastraea. Integr. Comp. Biol. 45, 342– 351. (10.1093/icb/45.2.342) 21676779

      Not checked in the free run.

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

    Interpretationnone given

    The transition to bilateral symmetry enabled directed movement, facilitated food search and avoided grazing the same area twice.

    “the transition to bilateral symmetry, which enabled directed movement, facilitated food search and avoided grazing the same area twice”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    These ectochoanocyte-derived cells would have constituted the first nerve net, which possibly controlled some form of amoeboid locomotion.

    “These latter cells would have constituted the first nerve net, which possibly controlled some form of amoeboid locomotion.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationcitation

    They were swimming or lived partially benthic in shallow waters, filtering and concentrating dissolved organic carbon and bacteria as microphageous suspension feeders.

    “They were swimming or lived partially benthic in shallow waters, filtering and concentrating dissolved organic carbon and bacteria as microphageous suspension feeders [3,15].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [3] Sperling EA, Vinther J 2010 A placozoan affinity for Dickinsonia and the evolution of Late Proterozoic metazoan feeding modes. Evol. Dev. 12, 201– 209. (10.1111/j.1525-142X.2010.00404.x) 20433459 source

      Not checked in the free run.

    • cites [15] Leys SP 2015 Elements of a ‘nervous system’ in sponges. J. Exp. Biol. 218, 581– 591. (10.1242/jeb.110817) 25696821 source

      Not checked in the free run.

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

    Interpretationreasoning

    Kopeocytes may have further diversified into cell types specializing in ciliary movement and control, mucus production and secretion of digestive enzymes, thus enabling external digestion and forming a mucociliary sole around the gastric opening.

    “Subsequently, the kopeocytes may have further diversified into cell types specializing in ciliary movement and control, mucus production and secretion of digestive enzymes, thus enabling external digestion and forming a ‘mucociliary sole’ around the gastric opening”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationnone given

    Digestion was intracellular at first and took place in the same multifunctional cells that also trapped the food.

    “However, digestion was intracellular at first and took place in the same multifunctional cells that also trapped the food—just as in unicellular eukaryotes.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    The sister cell-type concept posits that cell-type evolution can be resolved into a scheme of stepwise diversifications, giving rise to sister cell types.

    “The sister cell-type concept [5] posits that cell-type evolution can be resolved into a scheme of stepwise diversifications, giving rise to sister cell types [5]”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [5] Arendt D 2008 The evolution of cell types in animals: emerging principles from molecular studies. Nature reviews. Genetics 9, 868– 882. (10.1038/nrg2416) 18927580

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Five subfamilies of transient receptor potential (TRP) channels were present in early metazoans, among which TRPV channels likely played an ancient role in mechanosensation.

    “Five subfamilies of transient receptor potential (TRP) channels were present [24], among which TRPV (vanilloid TRP) channels likely played an ancient role in mechanosensation”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [24] Cai X, Clapham DE 2012 Ancestral Ca2+ signaling machinery in early animal and fungal evolution. Mol. Biol. Evol. 29, 91– 100. (10.1093/molbev/msr149) 21680871 PMC4037924

      Not checked in the free run.

    • cites [25] Fujiu K, Nakayama Y, Iida H, Sokabe M, Yoshimura K 2011 Mechanoreception in motile flagella of Chlamydomonas. Nat. Cell Biol. 13, 630– 632. (10.1038/ncb2214) 21478860

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    Strong support for the gastraea hypothesis comes from the prevalence of gastrula-like stages during animal development that are interpreted as recapitulation of the gastraea-like ancestral body plan.

    “From Haeckel's times until today, strong support for the gastraea hypothesis comes from the prevalence of gastrula-like stages during animal development that are interpreted as recapitulation of the gastraea-like ancestral body plan.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given

    The initial function of this nerve net might have been the control of amoeboid locomotion of the gastraea grazing on algal mats.

    “The initial function of this nerve net might have been the control of amoeboid locomotion of the gastraea, grazing on algal mats (resembling the movement of an amoeba, but at multicellular scale).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    TTF-2/foxE4, foxq1 and foxA are jointly expressed in the amphioxus and ascidian endostyle, a presumed homolog of the thyroidea harbouring mucus-secreting and motile ciliated cells, and this function is considered ancestral for chordates.

    “the thyroid-related transcription factors TTF-2/foxE4, foxq1 and foxA are jointly expressed in the amphioxus and ascidian endostyle, a presumed homolog of the thyroidea that harbours mucus-secreting and motile ciliated cells; and this function of the Fox genes is considered ancestral for the chordates [119].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [119] Hiruta J, Mazet F, Yasui K, Zhang P, Ogasawara M 2005 Comparative expression analysis of transcription factor genes in the endostyle of invertebrate chordates. Dev. Dyn. 233, 1031– 1037. (10.1002/dvdy.20401) 15861404

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Feeding traces indicate that Dickinsonia was grazing on the sea floor, which was covered by microbial mats.

    “Feeding traces indicate that one of the most characteristic fossils of the Ediacaran fauna, Dickinsonia, was grazing on the sea floor, which was covered by ubiquitous microbial mats [3] (figure 4a).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [3] Sperling EA, Vinther J 2010 A placozoan affinity for Dickinsonia and the evolution of Late Proterozoic metazoan feeding modes. Evol. Dev. 12, 201– 209. (10.1111/j.1525-142X.2010.00404.x) 20433459 source

      Not checked in the free run.

    • The authors state this as an assumption: Dickinsonia's entire ventral body surface was a digestive sole covered with mucus and cilia.

  • May combine two claims.

    Interpretationreasoning

    The neuromuscular orthogon and the mucociliary sole appear to have overlapped, because longitudinal muscles reach the gastric opening at least in cnidarians.

    “Importantly, neuromuscular orthogon and mucociliary sole appear to have overlapped, because longitudinal muscles reach the gastric opening (at least in cnidarians).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Ectodermal muscle fibres associated with the nerve are oriented longitudinally, parallel to the primary body axis, while the inner layer forms circular fibres.

    “As a rule, the ectodermal muscle fibres associated with the nerve are oriented longitudinally, that is in parallel to the primary body axis (while the inner layer forms circular fibres [61,62]).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [61] Hertwig O, Hertwig R 1879 Die Actinien. In Studien zur Blättertheorie. Jena, Germany: Gustav Fischer.

      Not checked in the free run.

    • cites [62] Hyman LH 1940 The invertebrates: protozoa through Ctenophora. New York, NY: McGraw-Hill Book Company.

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    foxj is an ancient key regulator of motile cilia biogenesis, conserved in cnidarians and sponges.

    “Most prominently, foxj has been identified as an ancient key regulator of motile cilia biogenesis [72,112,113], conserved in cnidarians [72] and even sponges [114].”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [72] Vij S et al. 2012 Evolutionarily ancient association of the FoxJ1 transcription factor with the motile ciliogenic program. PLoS Genet. 8, e1003019 (10.1371/journal.pgen.1003019) 23144623 PMC3493443

      Not checked in the free run.

    • cites [112] Stubbs JL, Oishi I, Izpisua Belmonte JC, Kintner C 2008 The forkhead protein Foxj1 specifies node-like cilia in Xenopus and zebrafish embryos. Nat. Genet. 40, 1454– 1460. (10.1038/ng.267) 19011629 PMC4648715

      Not checked in the free run.

    • cites [113] Yu X, Ng CP, Habacher H, Roy S 2008 Foxj1 transcription factors are master regulators of the motile ciliogenic program. Nat. Genet. 40, 1445– 1453. (10.1038/ng.263) 19011630

      Not checked in the free run.

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

    Premisecitation

    A choanocyte origin has been previously postulated for enterocytes and for flame cells based on morphological, functional and molecular resemblance.

    “A choanocyte-origin has been previously postulated for enterocytes [45] and for flame cells [46], based on morphological, functional and molecular resemblance.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [45] Takashima S, Gold D, Hartenstein V 2012 Stem cells and lineages of the intestine: a developmental and evolutionary perspective. Dev. Genes Evol. 223, 85– 102. (10.1007/s00427-012-0422-8) 23179635 PMC3873164

      Not checked in the free run.

    • cites [46] Jacobs DK, Nakanishi N, Yuan D, Camara A, Nichols SA, Hartenstein V 2007 Evolution of sensory structures in basal metazoa. Integr. Comp. Biol. 47, 712– 723. (10.1093/icb/icm094) 21669752

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The metazoan foxA, B, C, D and E subfamilies are evolutionarily related and resulted from duplications of an ancient precursor gene.

    “Interestingly, the metazoan foxA, B, C, D and E subfamilies are evolutionarily related [120–122] and resulted from duplications of an ancient precursor gene;”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [120] Adell T, Muller WE 2004 Isolation and characterization of five Fox (Forkhead) genes from the sponge Suberites domuncula. Gene 334, 35– 46. (10.1016/j.gene.2004.02.036) 15256253

      Not checked in the free run.

    • cites [121] Mazet F, Yu JK, Liberles DA, Holland LZ, Shimeld SM 2003 Phylogenetic relationships of the Fox (Forkhead) gene family in the Bilateria. Gene 316, 79– 89. (10.1016/S0378-1119(03)00741-8) 14563554

      Not checked in the free run.

    • cites [122] Magie CR, Pang K, Martindale MQ 2005 Genomic inventory and expression of Sox and Fox genes in the cnidarian Nematostella vectensis. Dev. Genes Evol. 215, 618– 630. (10.1007/s00427-005-0022-y) 16193320

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Placozoans move by ciliary gliding with the thick mucociliary sole facing the sea floor and by contraction of syncytial fibre cells.

    “Placozoans move by ciliary gliding with the thick mucociliary sole facing the sea floor, and by concomitant contraction of the syncytial fibre cells (figure 4b).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [104] Ruthmann A, Behrendt G, Wahl R 1986 The ventral epithelium of Trichoplax adhaerens (Placozoa): cytoskeletal structures, cell contacts and endocytosis. Zoomorphology 106, 115– 122. (10.1007/BF00312113)

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    The ectodermal nerve net essentially controlled body wall contractions, possibly mediating local to more widespread avoidance responses to mechanical stimuli.

    “Such an ectodermal nerve net essentially controlled body wall contractions, possibly mediating local to more widespread ‘avoidance’ responses to mechanical stimuli [141].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [141] Pantin CFA 1956 The origin of the nervous system. Pubbl. Staz. Zool. Napoli 28, 171– 181.

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Study design and conductreasoning

    In the absence of comparative molecular data for most cell types discussed, the postulated sequence of cell-type diversification events remains tentative.

    “Necessarily, in the absence of comparative molecular data for most of the cell types discussed here, the postulated sequence of cell-type diversification events underlying these transitions remains tentative.”
    Quote in the paperSubstantial claim

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

    Interpretationnone given

    Such locomotion required more sensory integration and coordination with increasing body size, and the increase in body size in turn resulted from the invention of the mucociliary sole with external digestion.

    “In essence, we hypothesize that such locomotion required more sensory integration and coordination with increasing body size (and that the increase in body size in turn resulted from the invention of the mucociliary sole with external digestion).”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Interpretationcitation

    Ediacaran fossils such as Dickinsonia had digestive diverticulae that have been compared with cnidarian pouches, implying that modern cnidarians resemble a grade of Late Precambrian organization from which bilaterians evolved.

    “These diverticulae have been compared with cnidarian pouches repeatedly [169,170] (figure 6e), which would imply that modern cnidarians resemble ‘a grade of Late Precambrian organization from which bilaterians evolved’ [171].”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [169] Valentine JW 1992 Dickinsonia as a polypoid organism. Palaeobiology 18, 178– 182. source

      Not checked in the free run.

    • cites [170] Malakhov VV 2004 New ideas on the origin of bilateral animals. Russ. J. Mar. Biol. 30, S22– S33. (10.1007/s11179-005-0019-4)

      Not checked in the free run.

    • cites [171] Budd GE, Jensen S 2000 A critical reappraisal of the fossil record of the bilaterian phyla. Biol. Rev. 75, 253– 295. (10.1017/S000632310000548X) 10881389 source

      Not checked in the free run.

  • May combine two claims.

    Interpretationnone given

    The evolutionary scenario explains the origin of Reissner's fibre but cannot explain why it is so persistent in extant vertebrates.

    “Our scenario explains the evolutionary origin of this fibre, yet cannot explain why it is so persistent in extant vertebrates.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationcitation

    The advantage of gastric pouches was extension of the internal resorptive surface, which would have intensified body physiology and probably allowed the maintenance and movement of larger body forms.

    “The obvious advantage of this innovation was the extension of the internal surface, i.e. the surface of the resorptive epithelium, and would have intensified body physiology and probably allowed the maintenance and movement of larger body forms [163]”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [163] Laflamme M, Xiao S, Kowalewski M 2009 From the cover: osmotrophy in modular Ediacara organisms. Proc. Natl Acad. Sci. USA 106, 14 438– 14 443. (10.1073/pnas.0904836106) PMC2732876 19706530 source

      Not checked in the free run.

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

    Interpretationcitation

    The first synapse arose from the aggregation of vesicle-related intercellular signalling modules, including synaptotagmin, SNARE-complex components and postsynaptic receptor complexes.

    “Similar ideas have been put forward repeatedly [5,66,67] and imply that the first synapse arose from the aggregation of vesicle-related intercellular signalling modules, including synaptotagmin, SNARE-complex components and postsynaptic receptor complexes, as extensively reviewed elsewhere [15,32,34,46,60].”
    Quote in the paperNot a substantial claim0 of 5 sources checked
    • cites [15] Leys SP 2015 Elements of a ‘nervous system’ in sponges. J. Exp. Biol. 218, 581– 591. (10.1242/jeb.110817) 25696821 source

      Not checked in the free run.

    • cites [32] Burkhardt P 2015 The origin and evolution of synaptic proteins—choanoflagellates lead the way. J. Exp. Biol. 218, 506– 514. (10.1242/jeb.110247) 25696814 source

      Not checked in the free run.

    • cites [34] Ryan TJ, Grant SG 2009 The origin and evolution of synapses. Nat. Rev. Neurosci. 10, 701– 712. (10.1038/nrn2717) 19738623

      Not checked in the free run.

    • cites [46] Jacobs DK, Nakanishi N, Yuan D, Camara A, Nichols SA, Hartenstein V 2007 Evolution of sensory structures in basal metazoa. Integr. Comp. Biol. 47, 712– 723. (10.1093/icb/icm094) 21669752

      Not checked in the free run.

    • cites [60] Nickel M 2010 Evolutionary emergence of synaptic nervous systems: what can we learn from the non-synaptic, nerveless Porifera? Invertebrate Biol. 129, 1– 16. (10.1111/j.1744-7410.2010.00193.x) source

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    In cerianthids, small multipolar neurons are the only neurons to directly receive sensory innervation, connect to each other, and directly innervate underlying myofibres via multiple collaterals, and they can be regarded as the core of the ancestral nerve net.

    “In cerianthids, these are the only neurons to directly receive sensory innervation, to connect to each other, and to directly innervate, via multiple collaterals, the underlying myofibres [128]; they can thus be regarded as the core of the ancestral nerve net [130].”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [128] Peteya DJ 1973 A light and electron microscope study of the nervous system of Ceriantheopsis americanus (Cnidaria, Ceriantharia). Z. Zellforsch. 141, 301– 317. (10.1007/BF00307408) 4147590

      Not checked in the free run.

    • cites [130] McFarlane ID 1984 Nerve nets and conducting systems in sea anemones: two pathways excite tentacle contractions in Calliactis parasitica. J. Exp. Biol. 108, 137– 149.

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    Glutamate was the first excitatory transmitter in nerve net neurons, and GABA acted as an inhibitory signal, possibly released in a refractory manner by the innervated muscle cells themselves.

    “These data suggest that glutamate was the first excitatory transmitter in nerve net neurons, and that GABA acted as an inhibitory signal, possibly released in a refractory manner by the innervated muscle cells themselves.”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [15] Leys SP 2015 Elements of a ‘nervous system’ in sponges. J. Exp. Biol. 218, 581– 591. (10.1242/jeb.110817) 25696821 source

      Not checked in the free run.

    • cites [156] Moroz LL et al. 2014 The ctenophore genome and the evolutionary origins of neural systems. Nature 510, 109– 114. (10.1038/nature13400) 24847885 PMC4337882 source

      Not checked in the free run.

    • cites [158] Delgado LM, Couve E, Schmachtenberg O 2010 GABA and glutamate immunoreactivity in tentacles of the sea anemone Phymactis papillosa (LESSON 1830). J. Morphol. 271, 845– 852. 20309875

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    External digestion with the mucociliary sole would have enabled external digestion and enhanced the concentration of nutrients in the gastric cavity.

    “First, external digestion with the mucociliary sole would have enabled external digestion and thus enhanced the concentration of nutrients in the gastric cavity.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationcitation

    The medial section of the bilaterian nerve cord corresponds to tissue of the former mucociliary sole and most probably evolved into the medial motor column, while the more lateral section evolved into lateral sensory-integrative columns.

    “The medial section corresponds to the tissue of the former mucociliary sole; this tissue most probably evolved into the medial motor column of the bilaterian nerve cord [44], and the more lateral section into the lateral sensory-integrative columns.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [44] Arendt D, Tosches MA, Marlow H In press From nerve net to nerve ring, nerve cord and brain—evolution of animal nervous systems. Nat. Rev. Neurosci. 26675821

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    The invention of gastric pouches predated the CBA, and this notion can be revived based on molecular evidence.

    “It has long been suggested that the invention of gastric pouches predated the CBA [164]; this notion can now be revived based on molecular evidence [44].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [164] Sedgwick A 1884 On the origin of metameric segmentation and some other morphological questions. Q. J. Microsc. Sci. 24, 43– 82.

      Not checked in the free run.

    • cites [44] Arendt D, Tosches MA, Marlow H In press From nerve net to nerve ring, nerve cord and brain—evolution of animal nervous systems. Nat. Rev. Neurosci. 26675821

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    The substantial increase of internal nutrient-resorbing surface via folding into gastric pouches might have boosted physiology and energy supply for locomotion, triggering regionalization and specialization of parts of the nerve net needed for more sophisticated and targeted movements.

    “Second, the substantial increase of the internal nutrient-resorbing surface via folding into gastric pouches might have boosted physiology and, consequently, energy supply for locomotion, thus triggering the regionalization and specialization of parts of the nerve net needed for the control of more sophisticated and targeted movements.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    With bilateral symmetry, body movement changed from multidirectional to unidirectional towards the new anterior end, allowing more targeted food search and avoiding already grazed areas.

    “Plausibly, body movement changed from multidirectional to unidirectional towards the new anterior end. This would have allowed more targeted food search and avoided passing through areas that had already been grazed (cf. figure 4a).”
    Quote in the paperNot a substantial claim
58 of 58

  • The paper relies on this without support.

    A nervous system was present in the last common ancestor of cnidarians and bilaterians (the cnidarian-bilaterian ancestor, CBA).

    “Almost certainly, a nervous system was present in the last common ancestor of cnidarians and bilaterians (cnidarian-bilaterian ancestor, CBA)”

  • The authors state this as an assumption.

    The ancient gastraea crept on the sea floor with the gastric opening facing downwards.

    “The ancient gastraea is originally assumed as creeping on the sea floor, with the gastric opening facing downwards”

  • The authors state this as an assumption.

    Dickinsonia's entire ventral body surface was a digestive sole covered with mucus and cilia.

    “It is assumed that their entire ventral body surface was a digestive ‘sole’ covered with mucus and cilia [3].”

  • The authors state this as an assumption.

    A nerve net existed in the last common ancestor of cnidarians, ctenophores and bilaterians (Neuralia), at the exclusion of sponges and placozoans.

    “As sponges and placozoans do not form a nerve net, the most parsimonious assumption appears to be that a nerve net existed in the last common ancestor of cnidarians, ctenophores and bilaterians (a grouping referred to as Neuralia by Nielsen [8]); yet, in light of the current uncertainties about the placement of the ctenophores [137], the existence of the ‘Neuralia’ at the exclusion of sponges and”

  • The authors state this as an assumption.

    The overall establishment of internal currents passing through the surface-extended pouches closely resembled that of some extant cnidarians.

    “Apart from that, we can assume that the overall establishment of internal currents passing through the surface-extended pouches might have closely resembled that of some extant cnidarians.”
5 of 5

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?

  • Ciliated mechanosensory cells in cnidarians are similar to vertebrate hair cells and may represent descendants of an ancient metazoan sensory cell type.

    “The ciliated mechanosensory cells in cnidarians are also similar to the hair cells of vertebrates, and may represent descendants of an ancient metazoan sensory cell type [64].”

    From Back to the Basics: Cnidarians Start to Fire (2017) · cites this paper as [64]

Cites

Flagged first, then by citations

3 of the 178 references couldn’t be matched to a known paper.

Research works printed but not linked: 7

  1. Haeckel E, 1874, Die Gastraea-Theorie, die phylogenetische Classification des Thierreiches und die Homologie der Keimblätter, Jena Z. Naturwiss, 8, 1
  2. Leadbeater BSC, 1983, Distribution and chemistry of microfilaments in choanoflagellates, with special reference to the collar and other tentacle systems, Protistologia, 10, 157
  3. Aiello E, 1974, Cilia and flagella, 353
  4. Arendt D, 2004, Gastrulation
  5. Hertwig O, 1879, Die Actinien. In Studien zur Blättertheorie
  6. Bullock TH, 1965, Structure and function in the nervous system of invertebrates
  7. Hernandez-Nicaise ML, 1991, Microscopic anatomy of the invertebrates, volume Placozoa, Porifera, Cnidaria, and Ctenophora, 359

Cited by

Sorted by citations

Related

Authors
Arendt, D., Benito-Gutierrez, E., Brunet, T., & Marlow, H.
Affiliations
  • Heidelberg University (DE)
  • European Molecular Biology Laboratory, Meyerhofstrasse 1, 69012 Heidelberg, Germany
  • European Molecular Biology Laboratory (DE)
Corresponding author
Arendt, Detlev
ORCID
Venue
Philosophical Transactions of the Royal Society B: Biological Sciences
Publisher
The Royal Society
Published
2015-12-19
Volume
370
Issue
1684
Pages
20150286
ISSN
  • 0962-8436 (ISSN-L)
  • 1471-2970
DOI
10.1098/rstb.2015.0286
PMC
PMC4650134
OpenAlex
W2178149281
Cited by
112
References
178
Citations by year
2026: 6 · 2025: 11 · 2024: 8 · 2023: 19 · 2022: 7 · 2021: 12 · 2020: 5 · 2019: 16 · 2018: 6 · 2017: 13 · 2016: 7 · 2015: 2
FWCI
1.18
Type
journal article
Language
en
Open access
Licence
Locations
  • Philosophical Transactions of the Royal Society B Biological Sciences (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • Apollo (University of Cambridge) (submittedVersion, cc-by)
  • Apollo (cc-by)
Topics
  • Physical Sciences › Earth and Planetary Sciences › Paleontology › Marine Invertebrate Physiology and Ecology
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Developmental Biology and Gene Regulation
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Planarian Biology and Electrostimulation
Keywords
nervous system evolution, gastric pouch, feeding behaviour, locomotion, nerve net, bilateral symmetry, Ediacaran fossils, Dickinsonia, cephalochordates, nutrient resorption
MeSH terms
Animals, Biological Evolution, Fossils, Nerve Net, Nervous System, Gastrointestinal Tract

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 2026-10-06.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-06.

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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