Phylogenetic Classification of Fossils with Recent Species

Abstract

Farris, J. S. (Département d'lnformatique et Centre de Recherches Mathematiques, Université de Montréal, Montréal, P.Q., Canada) 1976. Phylogenetic classification of fossils with recent species. Syst. Zool. 25:271–282.—Several aspects of present classificatory theory lead to logical weaknesses in phylogenetic classification and practical difficulties in classifying fossil forms. Modifications of classificatory methods are proposed to resolve these problems. The use of monotypic taxa has no logical basis and should be abandoned. (Species and genera must be exempted from this rule for reasons of nomenclature.) In consequence, sister groups may not be required to have the same rank. Phylogenetic classification can nonetheless properly represent sister group relationships. Categorical rank may not be determined by age of origin. Age of differentiation may be used to assign rank, as may temporal span: the elapsed time between the differentiation of a monophyletic group and the extinction of the group's last species (or the present, for living groups). Category names should be generated by a systematic rule, to avoid confusion if many ranks are required. Categorical ranks may not be analogized formally to integers, but should be regarded as rational numbers.