The Echinoid Directory

Contributed by Andrew Smith, August 2011

Pliocyphosoma Pomel, 1883, p. 90

[=Pomeliosoma Vadet, 2005, p. 136, type species Cyphosoma legayi Rigaux, 1882, by original designation.]

Diagnostic Features
  • Test circular and depressed.
  • Apical disc large and pentagonal, presumed monocyclic but not preserved.
  • Ambulacral plating polygeminate with plate compounding in diadematid style with all elements reaching the perradius.  Pore-pairs biserially arranged adapically and forming broad phyllodes adorally.
  • Interambulacral plates with dominant primary tubercle, sometimes with smaller secondary tubercles adradially.
  • All tubercles imperforate and crenulate.
  • Peristome large with feeble buccal notches.
  • Spines and lantern unreported.
Distribution Jurassic (Bathonian to Kimmeridgian), France
Name gender neuter
Type Pomel (1883, p. 90) listed six species under this genus - C. Douvillei, peroni, girumnense, archiaci, caratonianum and microtuberculatum. Type species Cyphosoma douvillei Cotteau, 1875, p. 181, by subsequent designation of Vadet, 2005, p. 134.
Species Included
  • P. douvillei (Cotteau, 1875); Oxfordian, France
  • P. morieri (Cotteau, 1883); Bathonian to Oxfordian, France
  • P. legayi (Rigayux, 1882); Kimmeridgian-Tithonian, France.
Classification and/or Status Carinacea, Phymosomatoida, Incertae sedis
Remarks It is unfortuante that the ambulacral plating in the type species is unknown.  However, in the other species assigned here it is polygeminate and diadematoid and so different from the phymosomatid style plating found in Phymosomatidae.  It closely resembles members of the Emiratiidae in its ambulacral plate compounding but can be immediately distinguished from them by its imperforate primary tubercles.

Pomel, A. 1883. Classification méthodique et Genera des Échinides vivante et fossiles. Thèses présentées a la Faculté des Sciences de Paris pour obtenir le Grade de Docteur ès Sciences Naturelles 503, Aldolphe Jourdan, Alger, 131 pp.

Vadet, A. 2005. Echiniodes fossils du Boulonnais: Du Bajocien au Tithonien Phymosomatoida Stomechinoida Arbacioida. Annales de la Societe d'Histoire Naturelle du Boulonnais 4(2), 110-156.