The Echinoid Directory

Order Holectypoida Duncan, 1889, p. 135


Irregular echinoids with:

  • large central peristome with buccal notches;
  • fully developed and functioning lantern throughout life;
  • perignathic girdle composed of auricles;
  • teeth wedge-shaped in cross-section;
  • apical disc compact;
  • ambulacral plates compound with three elements in each plate in acrosaleniid pattern (i.e. a simple plate alternates with two overlain by the primary ambulacral tubercle); on oral surface one or both smaller elements commonly reduced to demiplates;
  • Ambulacral pore-pairs not forming phyllodes adorally;
  • tubercles perforate and crenulate;
  • spines short, solid, without a cortex.
 Early Jurassic (Pliensbachian) to Late Cretaceous (Maastrichtian); worldwide.
Holectypoids are primitive irregular echinoids that possess a functional jaw apparatus and have a large central peristome. The periproct opens orally in Holectypina, but aborally in Pygasterina. Cassiduloids differ in having a much smaller peristome and have pore-pairs crowded adorally to form phyllodes.

Duncan, P. M. 1889. A revision of the genera and great groups of the Echinoidea. Journal of the Linnean Society, Zoology 23: 1-311.