Survival of crinoid stems following decapitation: evidence from the Ordovician and palaeobiological implications
Version of Record online: 2 JAN 2007
Volume 34, Issue 4, pages 263–270, December 2001
How to Cite
DONOVAN, S. K. and SCHMIDT, D. A. (2001), Survival of crinoid stems following decapitation: evidence from the Ordovician and palaeobiological implications. Lethaia, 34: 263–270. doi: 10.1111/j.1502-3931.2001.tb00055.x
- Issue online: 2 JAN 2007
- Version of Record online: 2 JAN 2007
- 28th November 2000, revised 18th June 2001.
It was recently discovered that the stems of extant crinoids may survive after detachment of the crown, presumably feeding by the absorption of nutrients through the ectoderm. Previously, only one analogous, albeit morphologically dissimilar, pattern of crownless survival has been recognized from the fossil record. Certain Upper Ordovician (Cincinnatian) crinoid pluricolumnals from Kentucky, Ohio and Indiana, derived from the disparids Cincinnaticrinus spp., have rounded terminations reminiscent of some modern bourgueticrinid overgrowths. Such specimens have hitherto been interpreted as distal terminations of mature individuals that have become detached from their attachment structures and taken to an eleutherozoic existence. However, it is considered more probable that they represent overgrowths of the column following predatory decapitation. If this new interpretation is correct, then post-decapitation survival of crinoid stems is now recognized for most of the history of the crinoids, ‘lethal’ predation on crinoid crowns occurred at least as early as the Late Ordovician and ancient crinoid populations can no longer be determined merely by counting crowns.