Cidaridae

Cidaridae is a family of sea urchins in the order Cidaroida. Cidarid sea urchins are characterized by their stout skeletton : 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...) · . The order Cidaroida is the basalmost of current sea urchins, and most of the species included in this family are abyssal, even if a handful of species remain quite common in tropical shallow waters, like Eucidaris or Phyllacanthus. According to the World Register of Marine Species (WoRMS), the following genera are included in this family A now abandoned genus, Cidarites was used in the late 18th and early 19th century to describe a number of species of both cidarid and echid sea urchins.