During the geologic history of crinoids, many groups have modified their distal stems to function as anchors in soft sediments, but more so in the Paleozoic than in later times. Major strategies were passively implanting anchors, cirral root systems, coils, and stemless reclining. In Paleozoic roots, the stereom usually consists of crystallographically individualized ossicles, but articulations may be hidden by a tough cuticle that protected the living tissue of immersed parts and stiffened them with cortical stereom. Post-Paleozoic representatives produced similar anchoring structures by different fabricational pathways, including non-articulated root systems.

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