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Peer-reviewedCC BY 4.0Scientific Reports

Morphology of the Devonian mandibulate arthropod Rhyniognatha and its implications for the timing of insect evolution

  • Emma J. Long1,2,3
  • Gregory D. Edgecombe2
  • Markus Koch4
  • Xiaoya Ma1
4 affiliations
  1. 1Centre for Ecology & Conservation, University of Exeter, Penryn Campus, Penryn, TR10 9FE Cornwall UK
  2. 2Science Group, The Natural History Museum, Cromwell Road, London, SW7 5BD UK
  3. 3Scientific Research, The British Museum, Great Russell Street, London, WC1B 3DG UK
  4. 4Bonn Institute of Organismic Biology, Section II: Animal Biodiversity, University of Bonn, An der Immenburg 1, 53121 Bonn, Germany
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Abstract

Insects are phenomenally diverse, yet their evolutionary origins remain poorly understood. The fossil Rhyniognatha hirsti from the Early Devonian Rhynie chert (ca. 408 Ma) has been widely accepted as the earliest insect and a crown-group pterygote (flying insect), based on the interpretation of short, dicondylic mandibles. For over two decades, this fragmentary specimen has served as a key calibration point in insect molecular phylogenies. An alternative hypothesis has proposed a myriapod affinity, citing ocular, antennal and maxillary structures. Here, we re-examine Rhyniognatha using confocal laser scanning microscopy. We find no evidence for an anterior mandibular acetabulum, refuting true dicondyly and undermining its placement within Dicondylia (silverfish–pterygote clade). We re-assess the proposed centipede affinity, demonstrating that certain diagnostic features are more plausibly interpreted as exoskeletal folds, and that the mandibles lack a clear myriapod-type base plate. Comparative analysis reveals similarities with apterygote hexapods, including bifurcated maxillary endites and comb-like superlinguae, and myriapods, such as an edafopodan-like elongate suspensorium, but does not support assignment to any specific mandibulate lineage. Consequently, Rhyniognatha cannot be placed within crown-group Insecta and is unsuitable as a calibration fossil for insect evolution, shifting the minimum age of winged insects by approximately 80 million years.

Supplementary Information: The online version contains supplementary material available at https://doi.org/10.1038/s41598-026-70516-3.

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Cite

BibTeXRIS
BibTeX
@article{long2026morphology,
  title = {{Morphology of the Devonian mandibulate arthropod Rhyniognatha and its implications for the timing of insect evolution}},
  author = {Emma J. Long and Gregory D. Edgecombe and Markus Koch and Xiaoya Ma},
  journal = {Scientific Reports},
  year = {2026},
  month = sep,
  doi = {10.1038/s41598-026-70516-3},
  url = {https://doi.org/10.1038/s41598-026-70516-3},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - Morphology of the Devonian mandibulate arthropod Rhyniognatha and its implications for the timing of insect evolution
AU  - Emma J. Long
AU  - Gregory D. Edgecombe
AU  - Markus Koch
AU  - Xiaoya Ma
PY  - 2026
DA  - 2026/09/18
JO  - Scientific Reports
DO  - 10.1038/s41598-026-70516-3
UR  - https://doi.org/10.1038/s41598-026-70516-3
AB  - Insects are phenomenally diverse, yet their evolutionary origins remain poorly understood. The fossil Rhyniognatha hirsti from the Early Devonian Rhynie chert (ca. 408 Ma) has been widely accepted as the earliest insect and a crown-group pterygote (flying insect), based on the interpretation of short, dicondylic mandibles. For over two decades, this fragmentary specimen has served as a key calibration point in insect molecular phylogenies. An alternative hypothesis has proposed a myriapod affinity, citing ocular, antennal and maxillary structures. Here, we re-examine Rhyniognatha using confocal laser scanning microscopy. We find no evidence for an anterior mandibular acetabulum, refuting true dicondyly and undermining its placement within Dicondylia (silverfish–pterygote clade). We re-assess the proposed centipede affinity, demonstrating that certain diagnostic features are more plausibly interpreted as exoskeletal folds, and that the mandibles lack a clear myriapod-type base plate. Comparative analysis reveals similarities with apterygote hexapods, including bifurcated maxillary endites and comb-like superlinguae, and myriapods, such as an edafopodan-like elongate suspensorium, but does not support assignment to any specific mandibulate lineage. Consequently, Rhyniognatha cannot be placed within crown-group Insecta and is unsuitable as a calibration fossil for insect evolution, shifting the minimum age of winged insects by approximately 80 million years.  Supplementary Information: The online version contains supplementary material available at https://doi.org/10.1038/s41598-026-70516-3.
SN  - 2045-2322
ER  -