Possible Boundaries between Pseudoalbaillella and Follicucullus (Follicucullidae, Albaillellaria, Radiolaria): An Example of Morphological Information from Fossils and Its Use in Taxonomy

Abstract

Recently, a middle Permian radiolarian species was reassigned from Follicucullus monacanthus Ishiga et Imoto to Pseudoalbaillella monacantha on the basis of the diagnoses of the genera Pseudoalbaillella Ormiston et Babcock and Follicucullus Holdsworth et Jones. This revision results in redrawing of the boundary between the genera; however, different boundaries could be drawn using different perspectives. As an example of fossil morphological information and its use in taxonomy, this article discusses possible boundaries from the traditional, diagnostic, phylogenetic and evolutionary perspectives. We advocate using the diagnostic boundary (between Ps. monacantha and F. porrectus Rudenko) to avoid taxonomic confusion and inconvenience.