The ontogeny of cinctans (stem-group Echinodermata) as revealed by a new genus, Graciacystis, from the middle Cambrian of Spain

Samuel Zamora*, Imran A. Rahman, Andrew B. Smith

*Corresponding author for this work

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

5 Citations (Scopus)
420 Downloads (Pure)


A new cinctan echinoderm, Graciacystis ambigua gen. et sp. nov. from Cambrian Series 3 rocks of Spain, is described based on more than 100 articulated specimens that range from 6 to 14.5mm in thecal length. This material shows that Graciacystis ambigua, while plastic in thecal shape, is highly conservative in its thecal construction, with a fixed number of marginal plates and very limited addition of plates in the stele and ventral membrane through ontogeny. Ventral swellings on marginal elements are absent from the smallest specimens and become gradually more marked during growth. A cladistic analysis shows Graciacystis to be a basal cinctan, more derived than Sotocinctus and the Trochocystitidae and as sister group to a large clade formed by Sucocystidae+Gyrocystidae. The determinate growth pattern seen in Graciacystis seems to be the general pattern for all cinctans.

Original languageEnglish
Pages (from-to)399-410
Number of pages12
Issue number2
Publication statusPublished - 13 Mar 2013

Bibliographical note

accepted in revised form 4 September 2012


  • Echinoderms
  • stem-group
  • ontogeny
  • phylogeny
  • cinctans
  • Cambrian

Cite this