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The youngest ctenocystoids from the Upper Ordovician of the United Kingdom and the evolution of the bilateral body plan in echinoderms

Research output: Contribution to journalArticle (Academic Journal)

  • Imran A. Rahman
  • Sarah Stewart
  • Samuel Zamora
Original languageEnglish
Pages (from-to)39-48
Number of pages10
JournalActa Palaeontologica Polonica
Issue number1
Early online date24 Mar 2014
DateE-pub ahead of print - 24 Mar 2014
DatePublished (current) - 2015


During the early Palaeozoic, echinoderm body plans were much more diverse than they are today, displaying four distinct types of symmetry. This included the bilateral ctenocystoids, which were long thought to be restricted to the Cambrian. Here, we describe a new species of ctenocystoid from the Upper Ordovician of Scotland (Conollia sporranoides sp. nov.). This allows us to revise the genus Conollia, which was previously based on a single poorly-known species from the Upper Ordovician of Wales (Conollia staffordi). Both these species are characterized by a unique morphology consisting of an elongate-ovoid body covered in spines, which clearly distinguishes them from their better-known Cambrian relatives; they are interpreted as semi-infaunal burrowers from deep-water environments. This indicates that the ctenocystoid body plan was not fixed early in the evolution of the group, and they most likely modified their structure as an adaptation to a new mode of life in the Ordovician.

    Research areas

  • Echinodermata, Ctenocystoidea, evolution, bilateral symmetry, body plans, Ordovician, United Kingdom

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