A PHYLOGENETIC STUDY OF TITI MONKEYS, GENUS CALLICEBUS, BASED ON CRANIAL MEASUREMENTS .1. PHYLETIC GROUPS OF CALLICEBUS

Examinations of 23 forms of Callicebus were made to elucidate their phylogenetic relationships based on cranial measurements. Multivariate statistical methods of distance analysis utilizing Q-mode correlation coefficients and principal component analysis were employed. As a result, the following five distinct groups were recognized morphometrically among the 23 species and subspecies: the Donacophilus, Cupreus, Moloch, Personatus, and Torquatus groups. Moreover, the phenetic characters of cranial size, karyotype, pelage coloration, and geographic range were consistent with the results of this group classification. It could be safely concluded therefore that these groups represented phylogenetically independent groups, in view of the fact that the rate of character differentiation was not appreciably different among closely related groups. Of the five groups, the Personatus and Torquatus groups were respectively considered to maintain a higher peculiarity of character differentiation within the Callicebus phylogeny, since these two groups individually displayed the higher magnitudes of differentiation in both their craniometric shape and some phenetic features. Conversely, the other three groups were considered to be closer to each other in the Callicebus phylogeny.