Cidaridae

Cidaridae is a family of sea urchins in the order Cidaroida.

== Description and characteristics == thumb|Typical Test (biology)|test of a cidarid sea urchin ([[Phyllacanthus imperialis).]] Cidarid sea urchins are characterized by their stout skeleton : the test is thick and hard, with massive perforated tubercles (never crenulated) surrounded by a crown of secondary tubercles, but no primary tubercles in the interambulacra regions. These tubercles hold massive spines, thick, strong and often very long, and showing sometimes odd shapes (thorny spines, fans, clubs, Christmas trees...).