The Jurassic crinoid genus Cyclocrinus D’ORBIGNY, 1850: still an enigma

Abstract

A rich collection of isolated columnals and fragmentary pluricolumnals, varying considerably in size, shape, and sculpture, from the Upper Oxfordian of the Couiavia region (northwestern Central Poland), is the basis for a critical discussion of the crinoid genus Cyclocrinus and its species. These are all based on dissociated columnals with tuberculate articular faces, and all with similar if not identical arrays of tubercles. The collection studied contains tuberculate columnals, as well as those with plain articular faces, which acquire tuberculation when etched with acids. This indicates the corrosional nature of tuberculation in the newly established species, Cyclocrinus couiavianus sp.nov., and in all other Cyclocrinus material. The structure of fragmentary pluricolumnals, whose arching and branching are reminiscent of root systems of some bourgueticrinids, would suggest that all Cyclocrinus material represents nothing else but modified radicular cirrals of unrecognizable members of the order Bourgueticrinida SIEVERTS-DORECK, 1953, rather than Cyrtocrinida or Millericrinida as previously assumed.