Synteny of human chromosomes 14 and 15 in the platyrrhines (Primates, Platyrrhini)

In order to study the intra- and interspecific variability of the 14/15 association in Platyrrhini, we analyzed 15 species from 13 genera, including species that had not been described yet. The DNA libraries of human chromosomes 14 and 15 were hybridized to metaphases of Alouatta guariba clamitans, A. caraya, A. sara, Ateles paniscus chamek, Lagothrix lagothricha, Brachyteles arachnoides, Saguinus midas midas, Leontopithecus chrysomelas, Callimico goeldii, Callithrix sp., Cebus apella, Aotus nigriceps, Cacajao melanocephalus,Chiropotes satanas and Callicebus caligatus. The 14/15 hybridization pattern was present in 13 species, but not in Alouatta sara that showed a 14/15/14 pattern and Aotus nigriceps that showed a 15/14/15/14 pattern. In the majority of the species, the HSA 14 homologue retained synteny for the entire chromosome, whereas the HSA 15 homologue displayed fragmented segments. Within primates, the New World monkeys represent the taxon with the highest variability in chromosome number (2n = 16 to 62). The presence of the HSA 14/15 association in all species and subspecies studied herein confirms that this association is the ancestral condition for platyrrhines and that this association has been retained in most platyrrhines, despite the occurrence of extensive inter- and intrachromosomal rearrangements in this infraorder of Primates.     

Phylogenetic relationships of the New World monkeys (Primates, platyrrhini) based on nuclear G6PD DNA sequences

In order to test hypotheses about the phylogenetic relationships among living genera of New World monkeys, 1.3 kb of DNA sequence information was collected for two introns of the glucose-6-phosphate dehydrogenase (G6PD) locus, encoded on the X chromosome, for 24 species of New World monkeys. These data were analyzed using a maximum parsimony algorithm. The strict consensus of the three most-parsimonious gene trees that result shows support for the following clades: a pitheciine clade including Callicebus within which Chiropotes and Cacajao are sister taxa, an Alouatta-atelin clade within which Brachyteles is the sister taxon of Lagothrix and which is sister to another clade containing the callitrichines, and a callitrichine/Aotus/Cebus/Saimiri clade. Within the callitrichines, Callimico is the sister taxon of Callithrix. Cebus and Saimiri form a clade. These results are broadly consistent with previously published DNA sequence analyses of platyrrhine phylogeny and provide additional support for groupings provisionally proposed in those earlier studies. Nevertheless, questions remain as to the relative phylogenetic placement of Leontopithecus and Saguinus, the branching order within the Aotus/Cebus/Saimiri/callitrichine clade, and the placement of the pitheciine clade relative to the atelines and the callitrichines.     

Variation in maxillary sinus anatomy among platyrrhine monkeys

Variations in the maxillary sinus anatomy of extant and fossil catarrhine primates have been extensively examined using computed tomography (CT), and have potential utility for phylogenetic analyses. This approach has also been used to demonstrate its anatomical variation in eight of the 16 extant genera of platyrrhines and the absence of the sinus in Saimiri and Cacajao. We used this approach to evaluate the three-dimensional anatomy of the maxillary sinus in all extant platyrrhine genera, and here argue the phylogenic implications of this variation. This study confirms, for the most part, previous CT studies and augments them with the six genera not studied previously: Ateles, Lagothrix, Callithrix, Cebuella, Pithecia and Chiropotes. The entire maxilla is pneumatized by the sinus in the atelines, Cebus, and Callicebus, whereas the sinus pneumatizes only the medial part of the maxilla in the callitrichines and Aotus. Pithecia has a unique conformation in which the maxillary sinus and the expanded inferior meatus pneumatize the posteromedial and anterolateral parts of the entire maxilla, respectively. Chiropotes has no sinus, and the inferior meatus possibly expands into the area between the middle meatus and medial surface of the maxilla to disturb sinus formation, as in the case of its close relative Cacajao. Finally, we argue that the sinus that pneumatizes the entire maxilla is a primitive feature in extant platyrrhines and was probably shared by the last common ancestor of the anthropoids.     

Systematics and body size: implications for feeding adaptations in New World monkeys.

The relationship between body size and feeding ecology is well established for primates. It is argued that the evolutionary history of modern New World monkeys and, in particular, the path to attainment of current body size is significant in understanding the similarities and differences between dietary strategies and other ecological parameters of similar-sized monkeys. Current interpretations of New World monkey evolutionary relationships are reviewed. Based on a synthesis of available body weights and the assumption that the earliest New World monkeys weighed close to 1 kg, similar to modern Aotus and Callicebus, predicted patterns of body size change in each lineage are given. Restrictions on directions of body size change in primates are discussed, and it is shown that "Stanley's Rule" offers a good explanation for differing body size ranges in New and Old World anthropoids. Predicted ecological correlates to body size drawn from the mammalian literature are offered and tested using data on New World monkeys, which show some concurrence and several interesting departures from predicted patterns. Sexual dimorphism in body weight of New World monkey species is reviewed, based on the new summary of body weight data given.     

Species tree estimation for a deep phylogenetic divergence in the New World monkeys (Primates: Platyrrhini)

The estimation of a robust phylogeny is a necessary first step in understanding the biological diversification of the platyrrhines. Although the most recent phylogenies are generally robust, they differ from one another in the relationship between Aotus and other genera as well as in the relationship between Pitheciidae and other families. Here, we used coding and non-coding sequences to infer the species tree and embedded gene trees of the platyrrhine genera using the Bayesian Markov chain Monte Carlo method for the multispecies coalescent (?BEAST) for the first time and to compared the results with those of a Bayesian concatenated phylogenetic analysis. Our species tree, based on all available sequences, shows a closer phylogenetic relationship between Atelidae and Cebidae and a closer relationship between Aotus and the Cebidae clade. The posterior probabilities are lower for these conflictive tree nodes compared to those in the concatenated analysis; this finding could be explained by some gene trees showing no concordant topologies between Aotus and the other genera. Moreover, the topology of our species tree also differs from the findings of previous molecular and morphological studies regarding the position of Aotus. The existence of discrepancies between morphological data, gene trees and the species tree is widely reported and can be related to processes such as incomplete lineage sorting or selection. Although these processes are common in species trees with low divergence, they can also occur in species trees with deep and rapid divergence. The sources of the inconsistency of morphological and molecular traits with the species tree could be a main focus of further research on platyrrhines.     

New World monkey phylogeny based on X-linked G6PD DNA sequences

The Platyrrhini, or New World monkeys, are an infraorder of Primates comprised of 16 genera. Molecular phylogenetic analyses have consistently sorted these genera into three groups: the Pitheciidae (e.g., saki and titi monkeys), Atelidae (e.g., spider and howler monkeys), and Cebidae (e.g., night monkeys, squirrel monkeys, and tamarins). No consensus has emerged on the relationships among the three groups or within the Cebidae. Here, approximately 0.8 kb of newly generated intronic DNA sequence data from the X-linked glucose-6-phosphate dehydrogenase (G6PD) locus have been collected from nine New World monkey taxa to examine these relationships. These data are added to 1.3 kb of previously generated G6PD intronic DNA sequence data [Mol. Phylogenet. Evol. 11 (1999) 459]. Using distance and parsimony-based techniques, G6PD sequences provide support for an initial bifurcation between the Pitheciidae and the remaining platyrrhines, linking Atelidae and Cebidae as sister taxa. Bayesian methods provided a conflicting phylogeny with Atelidae as outgroup. Within the Cebidae, a sister relation between Aotus and the Cebus/Saimiri clade is favored by parsimony analysis, but not by other analyses. Potential reasons for the difficulty in resolving family level New World monkey phylogenetics are discussed.     

Immunodiffusion systematics of the primates. Part V. The Platyrrhini.

Evolutionary relationships between New World monkeys and marmoset genera and the place of the Ceboidea within the primates are considered in terms of the immunological specificity of ceboid proteins. Antigenic distances between the New World primates are measured using antisera produced in rabbits to nine ceboid genera: Alouatta, Aotes, Ateles, Callicebus, Cebus, Chiropotes, Lagothrix, Saimiri and Saguinus. A cladogram constructed on the basis of increasing degrees of antigenic distance between branches depicts Ceboidea as a monophyletic assemblage within which Alouatta is grouped with the Atelinae genera, Lagothrix and Ateles, Chiropotes joins Cacajao and Cebus joins Saimiri. The joining of the cebid genera Aotes and Callicebus with callithricid genera Callimico and Saguinus into a single complex lineage suggests that Cebidae is a paraphyletic or polyphyletic taxon. A phylogenetic taxonomy for Platyrrhini is proposed.     

Phylogeny and Evolution of Selected Primates as Determined by Sequences of the ε-Globin Locus and 5′ Flanking Regions

We studied phylogenetic relationships of 39 primate species using sequences of the -globin gene. For 13 species, we also included flanking sequences 5 of this locus. Parsimony analyses support the association of tarsiers with the anthropoids. Our analysis of New World monkeys supports the model in which the callitrichines form a clade with Aotus, Cebus, and Saimiri, with Cebus and Saimiri being sister taxa. However, analysis of the 5 flanking sequences did not support grouping the atelines with Callicebus and the pitheciins. Our data support the classification of platyrrhines into three families, Cebidae (consisting of Cebus, Saimiri, Aotus, and the callitrichines; Atelidae—the atelines; and Pitheciidae—Callicebus and the pithiciins. The strepsirhines form well-defined lemuroid and lorisoid clades, with the cheirogaleids (dwarf and mouse lemurs) and Daubentonia (aye-aye) in the lemuroids, and the aye-aye being the most anciently derived. These results support the hypothesis that nonhuman primates of Madagascar descended from a single lineage. Local molecular clock calculations indicate that the divergence of lemuroid and lorisoid lineages, and the earliest diversification of lemuroids, occurred during the Eocene. The divergence of major lorisoid lineages was probably considerably more recent, possibly near the Miocene–Oligocene boundary. Within hominoids some estimated dates differ somewhat from those found with more extensive noncoding sequences in the -globin cluster.     

Ancestry of a human endogenous retrovirus family.

The human endogenous retrovirus type II (HERVII) family of HERV genomes has been found by Southern blot analysis to be characteristic of humans, apes, and Old World monkeys. New World monkeys and prosimians lack HERVII proviral genomes. Cellular DNAs of humans, common chimpanzees, gorillas, and orangutans, but not lesser ape lar gibbons, appear to contain the HERVII-related HLM-2 proviral genome integrated at the same site (HLM-2 maps to human chromosome 1). This suggests that the ancestral HERVII retrovirus(es) entered the genomes of Old World anthropoids by infection after the divergence of New World monkeys (platyrrhines) but before the evolutionary radiation of large hominoids.     

Comparative and functional myology of the prehensile tail in new world monkeys

The caudal myology of prehensile-tailed monkeys (Cebus apella, Alouatta palliata, Alouatta seniculus, Lagothrix lagotricha, and Ateles paniscus) and nonprehensile-tailed primates (Eulemur fulvus, Aotus trivirgatus, Callithrix jacchus, Pithecia pithecia, Saimiri sciureus, Macaca fascicularis, and Cercopithecus aethiops) was examined and compared in order to identify muscular differences that correlate with osteological features diagnostic of tail prehensility. In addition, electrophysiological stimulation was carried out on different segments of the intertransversarii caudae muscle of an adult spider monkey (Ateles geoffroyi) to assess their action on the prehensile tail. Several important muscular differences characterize the prehensile tail of New World monkeys compared to the nonprehensile tail of other primates. In atelines and Cebus, the mass of extensor caudae lateralis and flexor caudae longus muscles is more uniform along the tail, and their long tendons cross a small number of vertebrae before insertion. Also, prehensile-tailed monkeys, especially atelines, are characterized by well-developed flexor and intertransversarii caudae muscles compared to nonprehensile-tailed primates. Finally, Ateles possesses a bulkier abductor caudae medialis and a more cranial origin for the first segment of intertransversarii caudae than do other prehensile-tailed platyrrhines. These myological differences between nonprehensile-tailed and prehensile-tailed primates, and among prehensile-tailed monkeys, agree with published osteological and behavioral data. Caudal myological similarities and differences found in Cebus and atelines, combined with tail-use data from the literature, support the hypothesis that prehensile tails evolved in parallel in Cebus and atelines. © 1995 Wiley-Liss, Inc.     

Morphology and locomotor adaptations of the foot in early Oligocene anthropoids

Newly discovered foot bones of Aegyptopithecus are described and compared to those of Apidium and Dolichocebus. Locomotor adaptations are inferred for African early Oligocene propliopithecids, parapithecids, and for Argentine early Oligocene Dolichocebus. All show an anthropoid grade of development in their foot anatomy. Tarsals of Aegyptopithecus compare best with those of Miocene hominoids. Apidium shares derived calcaneal features that link it with Old World monkeys. Dolichocebus exhibits a very generalized platyrrhine talar morphology akin to that seen in Saimiri, Callicebus, Cebus, and Aotus. The morphology of early Oligocene primate foot bones suggests that at least three quite distinct groups, corresponding to three recognized superfamilies, were present in the early Oligocene of South America and Africa.     

Phylogenomics of species from four genera of New World monkeys by flow sorting and reciprocal chromosome painting

Background

The taxonomic and phylogenetic relationships of New World monkeys (Platyrrhini) are difficult to distinguish on the basis of morphology and because diagnostic fossils are rare. Recently, molecular data have led to a radical revision of the traditional taxonomy and phylogeny of these primates. Here we examine new hypotheses of platyrrhine evolutionary relationships by reciprocal chromosome painting after chromosome flow sorting of species belonging to four genera of platyrrhines included in the Cebidae family: Callithrix argentata (silvered-marmoset), Cebuella pygmaea (pygmy marmoset), Callimico goeldii (Goeldi's marmoset) and Saimiri sciureus (squirrel monkey). This is the first report of reciprocal painting in marmosets.

Results

The paints made from chromosome flow sorting of the four platyrrhine monkeys provided from 42 to 45 hybridization signals on human metaphases. The reciprocal painting of monkey probes on human chromosomes revealed that 21 breakpoints are common to all four studied species. There are only three additional breakpoints. A breakpoint on human chromosome 13 was found in Callithrix argentata, Cebuella pygmaea and Callimico goeldii, but not in Saimiri sciureus. There are two additional breakpoints on human chromosome 5: one is specific to squirrel monkeys, and the other to Goeldi's marmoset.

Conclusion

The reciprocal painting results support the molecular genomic assemblage of Cebidae. We demonstrated that the five chromosome associations previously hypothesized to phylogenetically link tamarins and marmosets are homologous and represent derived chromosome rearrangements. Four of these derived homologous associations tightly nest Callimico goeldii with marmosets. One derived association 2/15 may place squirrel monkeys within the Cebidae assemblage. An apparently common breakpoint on chromosome 5q33 found in both Saimiri and Aotus nancymae could be evidence of a phylogenetic link between these species. Comparison with previous reports shows that many syntenic associations found in platyrrhines have the same breakpoints and are homologous, derived rearrangements showing that the New World monkeys are a closely related group of species. Our data support the hypothesis that the ancestral karyotype of the Platyrrhini has a diploid number of 2n = 54 and is almost identical to that found today in capuchin monkeys; congruent with a basal position of the Cebidae among platyrrhine families.

     

Insect prey foraging strategies in Callicebus oenanthe in northern Peru

Titi monkeys (genus Callicebus) are small-bodied platyrrhines that supplement their predominantly frugivorous diet with variable amounts of leaves, seeds, and/or arthropod prey. Notable interspecific variation in the amount of insect prey in the diet has been observed in Callicebus, ranging from 0% to 20%. In this study, I investigate the degree and type of prey foraging in a little-known species, Callicebus oenanthe inhabiting a fragmented, secondary forest on the foothills of the Andes in northern Peru. I present data on prey type, prey search and capture techniques, substrate/vegetation use, foraging height, prey capture efficiency, and seasonal variation of insect prey foraging in one group of C. oenanthe observed from January to August 2005. Insect prey accounted for 22% of the diet, the highest amount reported for any Callicebus species to date, and insects from at least six different orders were included. C. oenanthe was mainly an investigative forager of hidden prey, manipulating easy-to-open substrates such as rolled up leaves, and hunted ant swarms and larger insects opportunistically. Insect foraging was predominant during the dry season (26%) and decreased during the wet season (13%). The study group foraged mostly in the understory (2-6 m) within vine-laden shrubs and trees, which may conform to an anti-predator strategy of crypticity. Overall the group had an 83% insect capture success rate. These data suggest that insect prey is an important part of the diet of C. oenanthe and may be especially notable during periods of resource scarcity. This study adds to the knowledge concerning insect prey foraging in Callicebus, which can have an important role in defining ecological strategies in the selection of secondary protein food resources within a given ecosystem.     

Platyrrhine dental eruption sequences

To determine dental eruption sequences of extant platyrrhines, 367 mandibles and maxillae of informative juvenile specimens from all 16 genera were scored for presence of permanent teeth including three intermediate eruption stages following Harvati (Am J Phys Anthropol 112 (2000) 69-85). The timing of molar eruption relative to that of the anterior dentition is variable in platyrrhines. Aotus is precocious, with all molars erupting in succession before replacement of any deciduous teeth, while Cebus is delayed in M2-3 eruption relative to I1-2. Callitrichines have a distinct tendency toward delayed canine and premolar development. Platyrrhine eruption sequences presented here show some evidence of conformity to Schultz's Rule, with relatively early replacement of deciduous dentition in "slower"-growing animals. The relationship of dental eruption sequences to degree of folivory, body mass, brain mass, and dietary quality is also examined. The early eruption of molars relative to anterior teeth in Pithecia, Chiropotes, and Cacajao, in comparison to genera such as Ateles, Lagothrix, and Alouatta, showing relatively later eruption of the molars, appears to be consistent with current phylogenetic hypotheses. Schultz (Am J Phys Anthropol 19 (1935) 489-581) postulated early relative molar eruption as the primitive dental eruption schedule for primates. The extremely early molar eruption of Aotus versus Callicebus (where both incisors erupt before M2 and M3, with M3 usually last) may lend support to the status of Aotus as a basal taxon. The early relative molar eruption of the fossil platyrrhine species Branisella boliviana is also consistent with this hypothesis (Takai et al.: Am J Phys Anthropol 111 (2000) 263-281).     

金丝猴(Rhinopithecus)的某些结构特征

本文在对金丝猴的三个种群作系统解剖的基础上,与其他灵长类以及金丝猴的三个种群之间进行了比较。结果表明:在金丝猴与其他灵长类进行比较的44个项目中,金丝猴特有者9项;与叶猴相同而与其他灵长类不同者4项;与疣猴类的共同特征9项;与叶猴、类人猿和人相似而为其他猴类所不具备的特征有5项;与类人猿和人相似而为叶猴和其他猴类所不具备的特征有17项。因此,我们认为金丝猴的地位在叶猴之上,是猴超科(Cercopithecoidea) 中最进化的一个属,在灵长类系统发育中处于猴类与猿类之间的中间地位。在金丝猴三个种群之间互异比较中,相互不同的特征均超过60％,似乎完全有理由把它分立为三个种。     

Evolution of the SEC1 gene in New World monkey lineages (Primates, Platyrrhini)

The structure and evolution of the SEC1 gene were examined for the first time in New World primates of the genera Alouatta, Aotus, Ateles, Brachyteles, Callicebus, Callithrix, Cebus, Chiropotes, Lagothrix, Leontopithecus, Pithecia, Saguinus, and Saimiri. This gene has a high CG content (63.8%) and an estimated heterogeneous size ranging from 795 (Callithrix) to 1041 bp (Pithecia), due to numerous indel events. Similar to other fucosyltransferases, three conserved regions are shared by these primates, except for the callitrichines, Aotus and Pithecia, in which indel events resulted in premature stop codons that are related to the production of a supposedly non-functional protein. Phylogenetic analysis of the SEC1 gene, transition/transversion rates, and nucleotide sequence alignment support the hypothesis that primate SEC1 evolved by divergent evolution, and that the lack of activity in some lineages occurred independently at least twice in New World primates, once in the Aotus-Cebus-Callitrichinae group and again in Pithecia. Likelihood-based inference of ancestral states for the activity of SEC1 leads us to suppose that inactivation of SEC1 in the Callitrichinae was a result of a more complex series of events than in Pithecia.     

Polymorphism of visual pigment genes in the muriqui (Primates, Atelidae)

Colour vision varies within the family Atelidae (Primates, Platyrrhini), which consists of four genera with the following cladistic relationship: {Alouatta[Ateles (Lagothrix and Brachyteles)]}. Spider monkeys (Ateles) and woolly monkeys (Lagothrix) are characteristic of platyrrhine monkeys in possessing a colour vision polymorphism. The polymorphism results from allelic variation of the single-locus middle-to-long wavelength (M/L) cone opsin gene on the X-chromosome. The presence in the population of alleles coding for different M/L photopigments results in a variety of colour vision phenotypes. Such a polymorphism is absent in howling monkeys (Alouatta), which, alone among platyrrhines, acquired uniform trichromatic vision similar to that of Old World monkeys, apes, and humans through opsin gene duplication. Dietary and morphological similarities between howling monkeys and muriquis (Brachyteles) raise the possibility that the two genera share a similar form of colour vision, uniform trichromacy. Yet parsimony predicts that the colour vision of Brachyteles will resemble the polymorphism present in Lagothrix and Ateles. Here we test this assumption. We obtained DNA from the blood or faeces of 18 muriquis and sequenced exons 3 and 5 of the M/L opsin gene. Our results affirm the existence of a single M/L cone opsin gene in the genus Brachyteles. We detected three alleles with predicted lambdamax values of 530, 550, and 562 nm. Two females were heterozygous and are thus predicted to have different types of M/L cone pigment. We discuss the implication of this result towards understanding the evolutionary ecology of trichromatic vision.     

Chorionic gonadotropin has a recent origin within primates and an evolutionary history of selection

Chorionic gonadotropin (CG) is a critical signal in establishing pregnancy in humans and some other primates, but this placentally expressed hormone has not been found in other mammalian orders. The gene for one of its two subunits (CG beta subunit [CGbeta]) arose by duplication from the luteinizing hormone beta subunit gene (LHbeta), present in all mammals tested. In this study, 14 primate and related mammalian species were examined by Southern blotting and DNA sequencing to determine where in mammalian phylogeny the CGbeta gene originated. Bats (order Chiroptera), flying lemur (order Dermoptera), strepsirrhine primates, and tarsiers do not have a CGbeta gene, although they possess one copy of the LHbeta gene. The CGbeta gene first arose in the common ancestor of the anthropoid primates (New World monkeys, Old World monkeys, apes, and humans), after the anthropoids diverged from tarsiers. At least two subsequent duplication events occurred in the catarrhine primates, all of which possess multiple CGbeta copies. The LHbeta-CGbeta family of genes has undergone frequent gene conversion among the catarrhines, as well as periods of strong positive selection in the New World monkeys (platyrrhines). In addition, newly generated DNA sequences from the promoter of the CG alpha subunit gene indicate that platyrrhine monkeys use a different mechanism of alpha gene expression control than that found in catarrhines.     

Covariance structure in the skull of Catarrhini: a case of pattern stasis and magnitude evolution

The study of the genetic variance/covariance matrix (G-matrix) is a recent and fruitful approach in evolutionary biology, providing a window of investigating for the evolution of complex characters. Although G-matrix studies were originally conducted for microevolutionary timescales, they could be extrapolated to macroevolution as long as the G-matrix remains relatively constant, or proportional, along the period of interest. A promising approach to investigating the constancy of G-matrices is to compare their phenotypic counterparts (P-matrices) in a large group of related species; if significant similarity is found among several taxa, it is very likely that the underlying G-matrices are also equivalent. Here we study the similarity of covariance and correlation structure in a broad sample of Old World monkeys and apes (Catarrhini). We made phylogenetically structured comparisons of correlation and covariance matrices derived from 39 skull traits, ranging from between species to the superfamily level. We also compared the overall magnitude of integration between skull traits (r²) for all Catarrhini genera. Our results show that P-matrices were not strictly constant among catarrhines, but the amount of divergence observed among taxa was generally low. There was significant and positive correlation between the amount of divergence in correlation and covariance patterns among the 30 genera and their phylogenetic distances derived from a recently proposed phylogenetic hypothesis. Our data demonstrate that the P-matrices remained relatively similar along the evolutionary history of catarrhines, and comparisons with the G-matrix available for a New World monkey genus (Saguinus) suggests that the same holds for all anthropoids. The magnitude of integration, in contrast, varied considerably among genera, indicating that evolution of the magnitude, rather than the pattern of inter-trait correlations, might have played an important role in the diversification of the catarrhine skull.     

COII: a useful tool for inferring phylogenetic relationships among New World monkeys (Primates, Platyrrhini)

In this study we evaluated the performance of the cytochrome c oxidase subunit II (COII) mitochondrial gene as a tool for inferring phylogenetic relationships among platyrrhines. Twenty-nine COII sequences were examined in seven platyrrhine genera ( Alouatta , Ateles , Lagothrix , Brachyteles , Cebus , Saimiri , and Aotus ) employing parsimony and distance methods. Phylogenetic signal (g₁) was present in all codon positions, despite the transitional saturation detected at the third position. In tree reconstructions bootstrap support values decreased abruptly above the generic level. Parsimony trees based on weighted transversions (tv : ts, 10 : 1) at the third position showed similar topologies. The utility of COII in phylogenetic studies among platyrrhines seems to be limited, due to its low rate of replacement substitutions and a relatively fast saturation of silent substitutions at third codon positions. Our data suggest that its main utility in platyrrhine systematics lies at the intrageneric level.