The Echinoid Directory

 Cidaroids with:

• Rigidly sutured corona of relatively stout plates; ambulacral plates rather firmly bound to interambulacral plates.
• Apical disc dicyclic; firmly bound to corona.
• Interambulacra with one or two large primary tubercles that are perforate and crenulate.
• Ambulacra simple throughout but with every other plate with an enlarged marginal tubercle from the ambitus adorally.
• Pore-pairs alternately offset forming a biseries in each column.
• Spines relatively stout and cylindrical; shaft ornamented with coarse irregular pustules and finer granules.

Lower Jurassic (Pliensbachian) to Lower Cretaceous (Valanginian); Europe, North Africa, Madagascar.

Distinguished from almost all other cidaroids by having biserially offset pore-pairs. The structure of the pore-pairs, in which the two pores are separated by a prominent raised interporal partition, suggests this group is derived from members currently included in the Polycidaridae.  Tetracidaris has a similar ambulacral pore-pair arrangement but differs in having four columns of interambulacral plates at the ambitus.

Gregory J. W. 1900. The Echinoidea. Pp. 282-332 in E. R. Lankester (ed.) A Treatise on Zoology. A. & C. Black, London.