CLADID CRINOID (ECHINODERMATA) ANAL CONDITIONS AND A TERMINOLOGY PROBLEM

Analysis of anal plates of type species of the cladid crinoid genera (excluding codiacrinid and some gasterocomacids) recognizes 23 anal subconditions that are grouped into 4 categories: Pre-Standard, Standard, Post-Standard A, and Post-Standard B. The anal conditions reflect recognized general evolutionary trends within all orders of the cladids. This corrects, describes more precisely, and replaces the widely used terms "primitive" and "advanced" to describe anal conditions, either of which can occur in older or younger cladid crinoids. We recommended that the morphologic terms primanal, secundanal, and tertanal replace the terms radianal, anal X, and right tube plate, respectively, in most cladid and flexible crinoids. Anal X should be used only for those genera where it has been demonstrated that the primanal was resorbed or migrated out of the cup. In most genera having cups with a single anal this rectifies the misnomer of referring to the single anal as anal X when it is actually the primanal that has migrated into the position previously occupied by the secundanal, pushing the secundanal out of the cup. The origin of cladid anals is not considered homologous to camerate anals, but the use of similar terms for descriptive purposes is given precedence over use of a misnomer. Recognition of the anal-plate positions and clarification of anal-plate homologies are important in cladid lineage and systematics investigations. Results of this study strongly support punctuated and mosaic evolution within the anal-plate series of cladid crinoids. Application of the new terminology further implies that the classification of some polyphyletic genera and families may be the result of convergence, wherein higher emphasis has been placed on the anal condition for family or superfamily assignment than has been placed on other equally significant morphologic features.