Cidaroida

Cidaroida,^[1] also known as pencil urchins,^[2] is an order of primitive sea urchins, the only living order of the subclass Perischoechinoidea. All other orders of this subclass, which were even more primitive than the living forms, became extinct during the Mesozoic.

Cidaroida Temporal range: Lower Permian–Recent PreꞒ Ꞓ O S D C P T J K Pg N
Cidaris cidaris
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Echinodermata
Class:	Echinoidea
Subclass:	Perischoechinoidea
Order:	Cidaroida Claus, 1880
Families
See text

Description

Their primary spines are much more widely separated than in other sea urchins, and they have no buccal slits. Other primitive features include relatively simple plates in the test, and the ambulacral plates continuing as a series across the membrane that surrounds the mouth.

Families

Many different fossil cidaroid radiola (spines) at the MNHN

According to World Register of Marine Species:^[1]

• family Anisocidaridae Vadet, 1999 †
• superfamily Cidaroidea Gray, 1825
  • family Cidaridae Gray, 1825
  • family Ctenocidaridae Mortensen, 1928a
  • family Paurocidaridae Vadet, 1999a †
• family Diplocidaridae Gregory, 1900 †
• family Heterocidaridae Mortensen, 1934 †
• superfamily Histocidaroidea Lambert, 1900
  • family Histocidaridae Lambert, 1900
  • family Psychocidaridae Ikeda, 1936
• family Miocidaridae Durham & Melville, 1957 †
• family Polycidaridae Vadet, 1988 †
• family Rhabdocidaridae Lambert, 1900 †
• family Serpianotiaridae Hagdorn, 1995 †
• family Triadocidaridae Smith, 1994c †

• 
  Stylocidaris affinis (Cidaridae)
• 
  Notocidaris sp. (Ctenocidaridae)
• 
  Histocidaris variabilis (Histocidaridae)
• 
  Tylocidaris ohshimai (Psychocidaridae)
• 
  Miocidaris coaeva (Miocidaridae, fossil)
• 
  Paracidaris florigemma (Polycidaridae, fossil)

• 
  Cidaris blakei, abyssal Caribbean species
• 
  Eucidaris tribuloides, shallow Caribbean species
• 
  Phyllacanthus imperialis, shallow Indo-Pacific species
• 
  Plococidaris verticillata, rare shallow Indo-Pacific species
• 
  Prionocidaris baculosa, from Philippines
• 
  Chondrocidaris gigantea, from Hawaii

References

Citations

1. Kroh, A.; Hansson, H. (2013). "Cidaroida". WoRMS. World Register of Marine Species. Retrieved 2013-12-31.
2. 250 Million Years of Bindin Evolution

Sources

• World Register of Marine Species link: Cidaroida Claus, 1880 (+species list)
• Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. p. 980. ISBN 0-03-056747-5.
• National History Museum. "Cidaroida". Retrieved 20 Dec 2009.