Contributed by Andrew Smith, May 2011
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. |