The Echinoid Directory

Suborder Clypeasterina L. Agassiz, 1835

[=Clypeasteroina Nisiyama, 1968, p. 28]

Diagnosis	Clypeasteroids with: internal buttressing in the form of concentric walls around the periphery with or without more central pillars; a pair of sunken and enclosed sphaeridia in each ambulacrum; petals when well developed consisting of alternating primary plates and demiplates (N. B. apetalloid forms with simple ambulacral plating); perignathic girdle of 5 pairs of ambulacral elements (auricles); interambulacral plating on oral surface always disjunct.
Range	Late Eocene to Recent; worldwide.

Diagnosis

Clypeasteroids with:

internal buttressing in the form of concentric walls around the periphery with or without more central pillars;
a pair of sunken and enclosed sphaeridia in each ambulacrum;
petals when well developed consisting of alternating primary plates and demiplates (N. B. apetalloid forms with simple ambulacral plating);
perignathic girdle of 5 pairs of ambulacral elements (auricles);
interambulacral plating on oral surface always disjunct.

Range

Late Eocene to Recent; worldwide.

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