Synopsis

Fossil crinoids are only rarely described from complete skeletons, that is, from the attachment structure to the ends of the arms. The crinoid Floricolumnus (col.) girvanensis Donovan & Clark was originally described on the basis of its distinctive column only, particularly the inflated, serrated nodal columnals; the crown remains unknown. Floricolumnus (col.) is important, with nodal columnals representing potential intercontinental stratigraphic markers for the interval from the Lower–Middle Llandovery boundary to the mid-Middle Llandovery (that is, late Rhuddanian to mid-Aeronian). The discovery of the attachment structure of F. (col.) girvanensis is, therefore, significant. A long pluricolumnal is interpreted as a distal planar coiled attachment; a simple discoidal holdfast with an anastomosing sculpture may be a juvenile attachment. Erect protuberances on some nodal epifacets may be a stereomic reaction to embedding or boring epizoobionts.

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