REPEATED REGENERATION OF PIRASOCRINID CRINOID SPINES IN THE UPPER PENNSYLVANIAN AMES LIMESTONE, EAST-CENTRAL OHIO

Regeneration of portions of the crinoid endoskeleton following loss to predation attempts or autotomy is a well-known phenomenon. To date, however, most effort has focused on patterns, frequencies, and evidence of regeneration of arms and portions of the calyx, with few reports of unusual or significant regeneration-related features preserved in isolated ossicles. Here we describe tegmen spines belonging to undetermined pirasocrinid (poteriocrine cladid) crinoids from the Upper Pennsylvanian Ames Member of the Glenshaw Formation of east-central Ohio that display evidence for multiple episodes of breakage and regeneration. As evidenced by major size discontinuities along the length of single spines, some specimens regenerated as many as four times during the lifespan of the individual; such a pattern of repeated regeneration of a single skeletal element has not previously been documented. Given the position of these spines atop a highly elevated, mushroom-shaped anal sac, frequent snipping by predatory fishes seems the most likely interpretation for the observed pattern.