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
Cidaris cidaris
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Echinodermata
Class: Echinoidea
Subclass: Perischoechinoidea
Order: Cidaroida
Claus, 1880
Families

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Description

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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

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Many different fossil cidaroid radiola (spines) at the MNHN

According to World Register of Marine Species:[1]

References

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Citations

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

Sources

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