Principles of classification of stems of ancient sea lilies

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Principles are elucidated for the classification of crinoid stems. The stem evolved towards greater length and flexibility. The axial canal decreased in size, some segments fused, ligamental areas became more developed, and the segments became lower. The stems are herein divided into three main groups based on their symmetry. It is hoped that this morphological-functional analysis will enable a more objective approach to the systematic evaluation of the morphology of stems. -P. M. Kier.