RANGE OF VARIATION IN CALYX PLATE SCULPTURING CHARACTER STATES AMONG THE CRINOIDEA AND POTENTIAL FUNCTIONS

Calyx plate sculpturing is an important, yet under appreciated, aspect of crinoid skeletal morphology. Plate sculpturing is commonly a diagnostic character for species, and it may help to define genera. However, definition and variability of calyx plate structure have received very little attention.

In this study the range of variation from smooth plate sculpturing to the remarkable exoplacoid sculpturing of the Devonian Cupressocrinitidae is outlined, categorized, and defined. For example, a terminology is proposed to define the distinction between pustulose, nodose, and spinose sculpturing. Spinosity has been demonstrated to be an antipredation adaptation in crinoids and other marine invertebrates. Potential functions of other types of plate sculpturing has received little study and is very difficult to demonstrate. However, other potential functions could be for strengthening plates, defense against platyceratid gastropods, or anti-fouling by epizoans, such as bryozoans.