Compiles evidence for biotic interactions of both living and fossil crinoids to elucidate the role of biotic interactions in crinoid evolution. Direct interactions between crinoids and with other organisms are considered in the contexts of predation, competition, and associations (with polychaetes, molluscs, crustaceans and fish, and in terms of commensalism, stereomic malformations, epizoans and parasitism). Crinoids also modify their habitat to affect other organisms. Predation and competition are considered to have played significant roles in crinoid evolution.