Holotypes in the taxonomy of planktonic foraminiferal morphospecies

Abstract

The claim that holotypes serve as exemplars of morphology is examined in the context of planktonic foraminiferal taxonomy. A review of some species described over the past 90 years suggests that holotypes are selected subjectively, presumably guided by authors' conceptions of diagnostic characters. Evidence of their representative status is never provided. Seldom is the amount of material examined given. That holotypes serve as name-bearers and have no intrinsic status as exemplars is discounted. Although the holotype is rarely described, there is a typological bias in planktonic foraminiferal taxonomy because of the focus on nomenclatural types in accompanying imagery, and on the use of simply applied qualitative definitions. Commonly, type specimens are among the earliest recognized in a taxon and are selected prior to an understanding of its biogeography. Because taxa are distributed in niches within and among water masses in the global ocean, and are quite variable, holotypes are unlikely to be suitable as taxon-wide exemplars. Yet that is their present role. Population variation is under-reported in the literature. Selection of exemplars should be based on species-wide morphometric surveys of populations.