Endocast and bony labyrinth of a Devonian ‘placoderm’ challenges stem gnathostome phylogeny

Research output: Contribution to journalArticlepeer-review

Authors

  • You-an Zhu
  • Gavin Young
  • Yuzhi Hu
  • Mohamad Bazzi
  • Per Ahlberg
  • Min Zhu
  • Jing Lu

Colleges, School and Institutes

Abstract

Our understanding of the earliest evolution of jawed vertebrates depends on a credible phylogenetic framework for the jawed stem gnathostomes collectively known as ‘placoderms’. However, their relationships, and even whether ‘placoderms’ represent a single radiation or a paraphyletic array, remain contentious. Here we describe the endocranial cavity and bony labyrinth of Brindabellaspis stensioi, commonly recovered as a taxon of uncertain affinity branching near the base of ‘placoderms’. While some features of its braincase and endocast resemble those of jawless vertebrates, its inner ear displays a repertoire of crown gnathostome characters. Both parsimony and Bayesian analyses suggest that prevailing hypotheses of ‘placoderm’ relationships are unstable, with newly-revealed anatomy pointing to a radical revision of early gnathostome evolution. Our results call into question the appropriateness of arthrodire-like ‘placoderms’ as models of primitive gnathostome anatomy and raise questions of homology relating to key cranial features.

Details

Original languageEnglish
JournalCurrent Biology
Publication statusPublished - 25 Jan 2021

Keywords

  • early vertebrates, Jawed Vertebrates, crown-group gnathostomes, phylogenetic analysis, placoderms, devonian fish, evolution of brain, evolution of inner ear, evolution of endolymphatic system