Romundina and the evolutionary origin of teeth

Martin Rucklin, Philip C J Donoghue*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

28 Citations (Scopus)
319 Downloads (Pure)


Theories on the origin of vertebrate teeth have long focused on chondrichthyans as reflecting a primitive condition-but this is better informed by the extinct placoderms, which constitute a sister clade or grade to the living gnathostomes. Here, we show that 'supragnathal' toothplates from the acanthothoracid placoderm Romundina stellina comprise multi-cuspid teeth, each composed of an enameloid cap and core of dentine. These were added sequentially, approximately circumferentially, about a pioneer tooth. Teeth are bound to a bony plate that grew with the addition of marginal teeth. Homologous toothplates in arthrodire placoderms exhibit a more ordered arrangement of teeth that lack enameloid, but their organization into a gnathal, bound by layers of cellular bone associated with the addition of each successional tooth, is the same. The presence of enameloid in the teeth of Romundina suggests that it has been lost in other placoderms. Its covariation in the teeth and dermal skeleton of placoderms suggests a lack of independence early in the evolution of jawed vertebrates. It also appears that the dentition-manifest as discrete gnathal ossifications-was developmentally discrete from the jaws during this formative episode of vertebrate evolution.

Original languageEnglish
Article number20150326
Number of pages5
JournalBiology Letters
Issue number6
Publication statusPublished - 24 Jun 2015


  • Dental development
  • Evolution
  • Jawed vertebrates
  • Modularity
  • Placoderm


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