The phylogenetic position of the genera Caipora and Protopithecus within the Platyrrhini was investigated within a cladistic framework based on morphological characters with emphasis on patterns of tooth variation. A data matrix of 102 characters and 23 terminal taxa was subjected to analysis using a branch and bound option of the PAUP 4.0 Software. As a result, 40 equally most parsimonious trees were obtained. A strict consensus of these trees yielded a topology with 15 components with five unresolved trichotomies. The phylogenetic results show that the giant monkeys Caipora and Protopithecus should be recognized as typical atelins, belonging to the tribe Atelini, being both closely related to Ateles. The cranio-dental evidence supporting the Atelini clade are: 1) a rounded basal portion of the incisors; 2) I1-2 similar in size (height); 3) hypocone smaller than protocone in M2 and similar in size in M1; 4) metacone smaller than paracone in M1- 2; 5) metacrista developed in M1-2; and 6) postglenoid foramen reduced. Based on this phylogenetic data, the taxonomical interpretation that indicates Protopithecus as a member of Alouattini is refuted.
