Diagnosis and differentiation of the order primates

Abstract

We contrast our approach to a phylogenetic diagnosis of the order Primates, and its various supraspecific taxa, with definitional procedures. The order, which we divide into the semiorders Paromomyiformes and Euprimates, is clearly diagnosable on the basis of well-corroborated information from the fossil record. Lists of derived features which we hypothesize to have been fixed in the first representative species of the Primates, Euprimates, Strepsirhini, Haplorhini, and Anthropoidea, are presented. Our classification of the order includes both holophyletic and paraphyletic groups, depending on the nature of the available evidence. We discuss in detail the problematic evidence of the basicranium in Paleogene primates and present new evidence for the resolution of previously controversial interpretations. We renew and expand our emphasis on postcranial analysis of fossil and living primates to show the importance of understanding their evolutionary morphology and subsequent to this their use for understanding taxon phylogeny. We reject the much advocated “cladograms first, phylogeny next, and scenario third” approach which maintains that biologically founded character analysis, i.e., functional-adaptive analysis and paleontology, is irrelevant to genealogy hypotheses. Unlike the cladistic rules of operations demand, we advocate and use a priori weighting of characters. We discuss the evidence for the various proposed relationships of the earliest euprimates, the Adapidae and Omomyidae, and show that linking the former with living Strepsirhini and the latter with living Haplorhini does not depend on the assumption of the presence of soft-anatomical characters in the fossils. On the contrary, it is the sharing of derived hard anatomical features of the fossil taxa with the living groups which makes their possession of either strepsirhine or haplorhine “soft” attributes probable. We discuss the relative merits of the use of the grade concept (with its widely recognized implication of polyphyly) in attempts to group primates and maintain that there exists no evidence for either an “archaic primate” or a prosimian or an anthropoid grade. All the characters in the literature attributed to these are inherited from the first representatives of either the semiorder Paromomyiformes or the semiorder Euprimates or the semisuborder Anthropoidea. Consequently, we find neither descriptive nor didactic merit in gradal arrangements, the goals of which can be much better served by a phylogenetic (not cladistic) classification.