The Echinoid Directory

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Subclass Atelostomata von Zittel. 1879

Diagnosis	Bilaterally symmetrical irregular echinoids with the mouth displaced anteriorly and the posterior interambulacrum differentiated on the oral surface forming a plastron.  Periproct on or close to posterior surface.
Range	Early Jurassic to Recent, worldwide
Remarks	The higher grouping that unites Holasteroida and Spatangoida.  Stem group members comprise the paraphyletic disasteroids.