Constructional morphology of the stems of Pentacrinitidae, and mode of life of Seirocrinus

Abstract

Use of growth gradients which determine the functional morphology of crinoid stems is regarded as a means for reconstructing the evolutionary development of pentacrinitids. Contradictory interpretations of the way of life of the huge pentacrinitid Seirocrinus can be assessed by this method. The resulting reconstructions, together with other observations and estimations of the load capacity of fossil trunks to which colonies of this crinoid are fixed, seem to confirm the pseudoplanktonic model. A former model of the subsiding process of Seirocrinus colonies, having proved to be inconsistent with physical parameters, is revised.