Phylogenetic relationships of the ‘higher heterostracans’ (Heterostraci: Pteraspidiformes & Cyathaspididae), extinct jawless vertebrates.

Emma Randle, Robert Sansom

    Research output: Contribution to journalArticlepeer-review


    Heterostracans are a clade of extinct jawless fishes that were a large
    component of early vertebrate ecosystems. They are key members of the
    gnathostome stem, and as such they, are central to our interpretation and
    understanding of early vertebrate evolution. Our knowledge of
    heterostracan inter-relationships is incomplete, with previous phylogenetic
    analyses focusing on the intra-relationships of individual clades. The two
    largest clades of heterostracans, Cyathaspididae and Pteraspidiformes,
    comprise Janvier’s ‘higher heterostracans’ and have been interpreted as
    monophyletic sister groups. Here we present a new parsimony based
    phylogeny for the Pteraspidiformes and Cyathaspididae including
    quantitative data. Our results indicate the Cyathaspididae are a
    paraphyletic assemblage with respect to a monophyletic Pteraspidiformes
    (which includes the Psammosteidae). Furthermore, we show the
    Anchipteraspididae are sister group to the Pteraspidiformes, when using
    pteraspid-type bauplan to interpret their anatomy. Application of
    stratigraphic range data and congruence measures was used to assess the
    performance of different treatments of phylogenetic data in terms of
    stratigraphic consistency; equal weighting of quantitative and qualitative
    characters was found to consistently outperform implied weighting. Our
    combined results indicate that inclusion of quantitative characters can
    greatly improve resolution of ostracoderm phylogenies and provides a
    framework to consider the intra- and inter-relationships of heterostracans
    more broadly.
    Original languageEnglish
    JournalZoological Journal of the Linnean Society
    Early online date5 Jul 2017
    Publication statusPublished - 2017


    • Cyathaspididae
    • Devonian
    • Heterostraci
    • phylogenetics
    • Pteraspidiformes
    • Silurian
    • stratigraphic congruence


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