A sea lily anchors with a jointed calcite stalk topped by a crown of arms held into the flow, a posture that filters plankton efficiently. The stalk is segmented, and the same mutable collagenous tissue that lets other echinoderms shed body parts allows the column to break at a chosen joint.
Deep-sea observations recorded animals separating from the base and then pulling themselves along, arms sweeping and the remaining stalk trailing, at speeds measured in a few centimetres per second at best. The behaviour was documented in response to predators, and predation scars on both living and fossil crinoids fit the picture.
The old textbook image of a sedentary, defenceless filter feeder rooted for life was based on the visible anatomy rather than on observation, which was scarce before deep submersibles. It is still not clear how far an individual can travel, how often this happens in the wild, or whether the detached stalk base is regenerated.