The Echinoid Directory

Order Cidaroida Claus, 1880

Diagnosis Regular echinoids with:
  • test composed of 20 columns of plates; pairs of ambulacral columns alternating with pairs of interambulacral columns
  • ambulacral plating simple or at most pseudocompound (i.e. every second or third element enlarged to accommodate a larger tubercle and spine, but individual elements not fused together by tubercle overgrowth)
  • interambulacral plates dominated by a single large primary tubercle (except Tetracidaris which has two)
  • perignathic girdle of interambulacral elements only (apophyses).
  • ambulacral plates continuing as a series across the peristomial membrane
  • teeth crescentic to U-shaped in cross-section; pyramids without a foramen magnum
  • primary spines with external cortex (except in most primitive members)
  • globiferous and tridentate pedicellariae only.
Range Lower Permian to Recent; worldwide.
Type Type genus Cidaris Leske, 1778,  p. 74,
Remarks There is currently only a single order in the subclass Cidaroidea.  See Cidaroidea for key.

The following taxon is spine-based and probably belongs here:
Minicidaris Deraniyagala, 1961

Claus, C. F. W. 1880. Grundzuge der Zoologie. N. G. Elwertsche, Marburg & Leipzig. 1254 pp (4th edition).