Vertical posture of the clypeasteroid sand dollar Encope michelini

Abstract

Vertical posture has been studied only in the scutellid sand dollar Dendraster excentricus although it has been reported in another Dendraster species and two species of laganid sand-dollars. The vertical posture has been associated with the posterior eccentric position of the apical system and petals of the test. We have discovered the scutellid sand dollar Encope michelini, which shows no eccentricity of the apical system and petals, also has the vertical posture in the population studied. Absence of eccentricity of the apical system and petals in living and fossil sand-dollars does not indicate absence of the vertical posture.