Origins of the Ceboidea viewed from an immunological perspective

Ceboid origins were reviewed from the standpoint of immunodiffusion systematics. Computer processing of spur size data from several thousand trefoil Ouchterlony plate comparisons using rabbit antisera to proteins of various primate, tree shrew and elephant shrew species depicted antigenic distances among the various species. A least squares procedure (executed by a new computer program AJUST) corrected for nonreciprocity in the raw antigenic distance matrix. Another computer program (UWPGM) then produced a cladogram from the normalized antigenic distance matrix. Within the cladogram, tree shrews are closer to undisputed primates than to non-primates. The undisputed primates appear as a monophyletic assemblage, consisting of two major lineages: the Strepsirhini, including lorisoid and lemuroid branches, and the Haplorhini. Haplorhini divides into a tarsioid branch and Anthropoidea. The latter consists of two sister groups, Catarrhini (Hominoidea and Cercopithecoidea) and Platyrrhini (Ceboidea). Thus, this cladogram supports those hypotheses of ceboid origins which depict the phyletic line ancestral to the extant Anthropoidea as first separating from strepsirhine and tarsioid lineages before splitting apart into Platyrrhini and Catarrhini. Present evidence does not reveal if the most recent common ancestor of platyrrhines and catarrhines was morphologically still a prosimian or if it existed late enough in the Tertiary to have reached the simian grade.