Skip to content
DraconiticResearch
Search Sources API
197,693 studies31 sourcesUpdated 7 min ago
Peer-reviewedCC BY 4.0Royal Society Open Science

Reappraisal of the opercular anatomy in the ‘maxillate placoderms’ Entelognathus primordialis and Qilinyu rostrata

  • Donglin He1,2
  • Martin D. Brazeau3
  • Min Zhu1,2
  • You-an Zhu1,2
  1. 1Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences 1 , Beijing, People's Republic of China
  2. 2College of Earth and Planetary Sciences, University of Chinese Academy of Sciences 2 , Beijing, People's Republic of China
  3. 3Department of Life Sciences, Imperial College London 3 , Silwood Park Campus, Ascot, UK
Open at sourcePDFDOICite

Abstract

The Silurian ‘maxillate placoderms’ Entelognathus primordialis and Qilinyu rostrata were previously described as possessing a single dermal operculum, suspended by either an opercular cartilage or an antiarch-like dermal articulation, respectively. Here, we reinvestigate the holotypes of these taxa using synchrotron and micro-CT scanning data, revealing opercular morphologies distinct from prior descriptions. Instead of a single opercular plate as in other ‘placoderms’, Entelognathus possesses two dermal opercular plates arranged anteroposteriorly. The larger posterior plate bears a pronounced anterodorsal process, which was previously identified as the opercular cartilage. Both plates are extensively overlapped by the skull roof. The opercular morphology of Qilinyu, although consisting of a single opercular plate, shares features with that of Entelognathus, including a pronounced anterodorsal process and an extensive overlap by the skull roof. A comparison of the gill-covering structures in various early gnathostomes indicates that the described character combination is unique to the maxillate placoderms. The skull roof overlap suggests that the opercula of both taxa could slide along the visceral surface of the skull roof. Two new phylogenetic characters and several revised characters related to the operculum are proposed for an updated phylogenetic analysis of early jawed vertebrates. The Adams consensus tree from our analysis identifies phylogenetic signal for the monophyly of at least some of the maxillate placoderms.

Related

  1. The impact of perceived social support on college athletes’ academic burnout: The moderating role of cognitive reappraisal within a serial mediation model
    Guihua Xu, Xirui Yang, Qiyong Zhang
    PLOS OnePeer-reviewedCC BYFull textNeurosciencePsychiatry & mental healthPLOSEurope PMC
  2. Prospecting for informed dispersal: Reappraisal of a widespread but overlooked ecological process
    Aurore Ponchon
    EcologyPeer-reviewedCC BY 4.0Full text5 citedEcologyEnvironmental science & pollutionHAL
  3. Maternal Anxiety During Pregnancy and Offspring Information Processing Across Development: A Theory-Guided Predictive-Processing Reappraisal of Two Longitudinal Cohorts
    Bea R. H. Van den Bergh, Martin G. Frasch
    arXivPreprintCC BY-NC-ND 4.0Full textBioinformatics & computational biologyNeurosciencearXiv
  4. Miocene instead of cretaceous: a reappraisal of the age of Ethiopian amber
    Valentine Bouju, Vincent Perrichot, Alexander R Schmidt +6
    Gondwana ResearchPeer-reviewedCC BY 4.0Full textEvolutionary biologyGeology & geochemistryHAL
  5. Isoform inflation and annotation heterogeneity can confound Kunitz-repertoire comparisons in blood-feeding animals: a gene-level reappraisal
    F. Zhao, J. Zhao, F. Zhao
    bioRxivPreprintCC BYFull textEvolutionary biologyGenetics & genomicsbioRxiv

Cite

BibTeXRIS
BibTeX
@article{he2026reappraisal,
  title = {{Reappraisal of the opercular anatomy in the ‘maxillate placoderms’ Entelognathus primordialis and Qilinyu rostrata}},
  author = {Donglin He and Martin D. Brazeau and Min Zhu and You-an Zhu},
  journal = {Royal Society Open Science},
  year = {2026},
  month = sep,
  doi = {10.1098/rsos.260645},
  url = {https://royalsocietypublishing.org/rsos/article/13/9/260645/483421/Reappraisal-of-the-opercular-anatomy-in-the},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - Reappraisal of the opercular anatomy in the ‘maxillate placoderms’ Entelognathus primordialis and Qilinyu rostrata
AU  - Donglin He
AU  - Martin D. Brazeau
AU  - Min Zhu
AU  - You-an Zhu
PY  - 2026
DA  - 2026/09/30
JO  - Royal Society Open Science
DO  - 10.1098/rsos.260645
UR  - https://royalsocietypublishing.org/rsos/article/13/9/260645/483421/Reappraisal-of-the-opercular-anatomy-in-the
AB  - The Silurian ‘maxillate placoderms’ Entelognathus primordialis and Qilinyu rostrata were previously described as possessing a single dermal operculum, suspended by either an opercular cartilage or an antiarch-like dermal articulation, respectively. Here, we reinvestigate the holotypes of these taxa using synchrotron and micro-CT scanning data, revealing opercular morphologies distinct from prior descriptions. Instead of a single opercular plate as in other ‘placoderms’, Entelognathus possesses two dermal opercular plates arranged anteroposteriorly. The larger posterior plate bears a pronounced anterodorsal process, which was previously identified as the opercular cartilage. Both plates are extensively overlapped by the skull roof. The opercular morphology of Qilinyu, although consisting of a single opercular plate, shares features with that of Entelognathus, including a pronounced anterodorsal process and an extensive overlap by the skull roof. A comparison of the gill-covering structures in various early gnathostomes indicates that the described character combination is unique to the maxillate placoderms. The skull roof overlap suggests that the opercula of both taxa could slide along the visceral surface of the skull roof. Two new phylogenetic characters and several revised characters related to the operculum are proposed for an updated phylogenetic analysis of early jawed vertebrates. The Adams consensus tree from our analysis identifies phylogenetic signal for the monophyly of at least some of the maxillate placoderms.
SN  - 2054-5703
ER  -