Predation on crinoids

Over the last 25 years a conceptual shift has occurred in paleobiologists’ view of the importance of predation as an ecological and evolutionary force. The importance of predation pressure on crinoids and its effects on morphological evolution and on biogeographic patterns of this group serves as a clear illustration of this shift: whereas prior to the 1970’s crinoids were generally thought to be immune from predation, since then predation has been invoked as a probable cause of: (a) the success of extant stalkless crinoids, the comatulids, in shallow water settings (Meyer, 1977 and Macurda, 1977); (b) the retreat of isocrinids, a group of stalked crinoids, into deeper water since the Cretaceous that culminated in their present bathymetric distribution (Meyer, 1977 and Macurda, 1977; Meyer, 1985; Oji, 1996); (c) trends in arm morphology of isocrinids and comatulids (Oji, 1994 and Okamoto, 1994); (d) trends in cup plate thickness and spinosity in Devonian and post-Devonian crinoids (Signor, 1984 and Brett, 1984); (e) evolution of the cladid and disparid anal sac as an anti-predatory device (Lane, 1984); and (f) evolution of morphological and behavioral escape strategies among articulate crinoids (Baumiller, 2000), among others. In this chapter we will illustrate this conceptual shift using examples from the literature that span the interval of time during which this shift occurred, review some of the studies that present evidence of predation on crinoids and argue for its importance to their ecology and evolution, and, finally, provide additional data on predation from a couple of Paleozoic examples of regeneration.