Does similarity in rugosan characters and their functions indicate taxonomic relationship?

Functional analysis of changes in shape and arrangement of septa in the genera Zaphrentites, Caninia, and Ufimia allows one to move slightly beyond the usual boundaries of description and to ask why the arrangement in Zaphrentites is permanent, but becomes radial in Caninia and bilateral in Ufimia? This may be explained in terms of changing function and biological role of major septa in the ontogeny. eation of open space to accommodate strongly developed mesenteries is proposed as an explanation for the shortening and radial arrangement of axially free septa in mature Caninia, whereas the development of a slit on an oral disc, increasing water flow through the gastro-vascular cavity, is postulated for Ufimia. Both solutions point towards increased effectiveness of feeding and oxygenation, necessary for the growing organism. Such a conclusion negates the simple application of a given arrangement of septa as an indicator of taxonomic relationship.