A Bayesian approach to dynamic homology of morphological characters and the ancestral phenotype of jawed vertebrates

  1. Benedict King  Is a corresponding author
  2. Martin Rücklin
  1. Naturalis Biodiversity Center, Netherlands


Phylogenetic analysis of morphological data proceeds from a fixed set of primary homology statements, the character-by-taxon matrix. However, there are cases where multiple conflicting homology statements can be justified from comparative anatomy. The upper jaw bones of placoderms have traditionally been considered homologous to the palatal vomer-dermopalatine series of osteichthyans. The discovery of 'maxillate' placoderms led to the alternative hypothesis that 'core' placoderm jaw bones are premaxillae and maxillae lacing external (facial) laminae. We introduce a BEAST2 package for simultaneous inference of homology and phylogeny, and find strong evidence for the latter hypothesis. Phenetic analysis of reconstructed ancestors suggests that maxillate placoderms are the most plesiomorphic known gnathostomes, and the shared cranial architecture of arthrodire placoderms, maxillate placoderms and osteichthyans is inherited. We suggest that the gnathostome ancestor possessed maxillae and premaxillae with facial and palatal laminae, and that these bones underwent divergent evolutionary trajectories in placoderms and osteichthyans.

Data availability

Taxon sources, character list, the data matrix in nexus format and the BEAST2 xml file are available for review at https://figshare.com/s/e40652290467d2a436fd.

Article and author information

Author details

  1. Benedict King

    Naturalis Biodiversity Center, Leiden, Netherlands
    For correspondence
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-9489-8274
  2. Martin Rücklin

    Naturalis Biodiversity Center, Leiden, Netherlands
    Competing interests
    The authors declare that no competing interests exist.


Nederlandse Organisatie voor Wetenschappelijk Onderzoek (Vidi 864.14.009)

  • Benedict King
  • Martin Rücklin

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Reviewing Editor

  1. Min Zhu, Chinese Academy of Sciences, China

Version history

  1. Received: August 22, 2020
  2. Accepted: December 3, 2020
  3. Accepted Manuscript published: December 4, 2020 (version 1)
  4. Version of Record published: January 8, 2021 (version 2)


© 2020, King & Rücklin

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.


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  1. Benedict King
  2. Martin Rücklin
A Bayesian approach to dynamic homology of morphological characters and the ancestral phenotype of jawed vertebrates
eLife 9:e62374.

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