A revised taxonomy of Cenozoic radiolarian families is of particular importance because exhaustive molecular phylogenetic analyses for Collodaria, Entactinaria, Nassellaria and Spumellaria have shown high level of confidence at family or higher taxonomic ranks. In this sense, this study presents a new comprehensive taxonomy at the family level that integrated a classification based on ribosomal taxonomic marker genes (rDNA) and classical morphological taxonomy. However, many family names commonly used in Cenozoic radiolarians (Polycystinea) are derived from genera whose type species were never illustrated at the time of the generic definition. Obviously, in the vast majority of those cases, the “Principle of Typification” regulated in the International Code of Zoological Nomenclature (ICZN 1999: Art. 61) cannot be logically applied. This has contributed to a century-long misunderstanding about the validity of Cenozoic taxa (species, genera and/or family-group names) erected without any illustration or drawing of their types, in particular the huge contribution of Ernst Haeckel from samples of the Challenger expedition (1872-1876). Reexamination of Haeckel's collection definitively confirmed that all the original types series (the specimens on which Haeckel established the nominal species-group taxon) being nonextant; in other words, all name-bearing specimens (the types) are restricted to the illustrations given in Haeckel's drawings. Because “types” in taxonomy are precious things, a nominal species-group taxon lacking at all of illustration (or indication to a repository) do not ensure the recognition of the species. Following the rules and recommendations of the ICZN, these names should be excluded from all nomenclatorial and taxonomical acts. This revision presents the state of the art of all proposed family-group names (with full synonymy lists) for Cenozoic Polycystinea.

The list of family-group nominal taxa and their names was inventoried from 6694 publications (89% of the whole known references on radiolarians). The references were examined in order to clarify and fix the status of family names; hence these family-group names were rigidly classified as: valid, junior synonym, nomen dubium, nomen nudum, homonym, and invalid names. A total of 372 family-group names were proposed for the Cenozoic. These consist of 94 valid family-groups, 118 junior synonym family-groups, 111 nomen dubium family-groups (mainly artificially created in a hypothetical conceptual framework), 6 junior homonym family-groups, 19 nomen nudum family-groups, as well as 24 invalid names. In addition, one nomen novum et four new families are presented. The description of 25 families have been also emended.

This study also outlines the advantages of an integrated approach to taxonomy of Polycystinea by the combination of both morphological and molecular systematics. Based on molecular phylogenetic studies, the systematic classification proposed at suprageneric level is arranged as follows: