ABSTRACT
Calceocrinids exploited a unique life style. The crown was movably hinged to a recumbent stem. Ontogenetic studies of two primitive Ordovician calceocrinids disclose solutions to the functional problems faced by these organisms. In order to open the crown into the feeding position, the hinge was either isometric or positively allometric relative to the effective weight of the crown. The food-gathering capacity of a crinoid can be estimated by the number of food-catching tube-feet multiplied by the width of the food grooves which reflects the number and size of the food particles that can be collected. The food-gathering capacity was subject to marked positive allometry compared to the volume of the crown.
