After a comatulid sheds its postlarval stalk, it retains only the topmost segment, a large modified ossicle called the centrodorsal , located in the middle of the aboral surface.
Ligaments attach the cirri to sockets in the centrodorsal.
All comatulids apparently develop five initial, radially-oriented cirri. However, the pattern of marginal cirrus addition remains the same. In some thalassometrids and antedonids, small apical cirri developed when the comatulid was young are retained near the top of a conical or hemispherical centrodorsal. Alternatively, they may be lost, with traces of their attachment remaining as obsolete sockets. In both cases, however, at least a small area devoid of cirri and sockets, the aboral pole , remains at the centrodorsal apex.