An epibiont and the functional morphology of the column of a platycrinitid crinoid

Abstract
SUMMARY: The columns of the Upper Palaeozoic, monobathrid platycrinitid crinoids are generally considered to be highly flexible due to the presence of well developed synarthrial articulations. However, in some species these are modified to symplectial or syzygial articulations of unusual geometry. That the latter are essentially inflexible is suggested by a unique specimen from the Brigantian of Coverdale, Yorkshire, intimately encrusted during life by the tabulate coral Cladochonus. Such rigid articulations are associated with the attachment structure, giving these crinoids a particularly xenomorphic column with respect to articulation, despite a conservative external appearance which may lead to erroneous deductions concerning function.