Fossil Platyrrhines Research Articles

Total evidence phylogeny of platyrrhine primates and a comparison of undated and tip-dating approaches

There have been multiple published phylogenetic analyses of platyrrhine primates (New World monkeys) using both morphological and molecular data, but relatively few that have integrated both types of data into a total evidence approach. Here, we present phylogenetic analyses of recent and fossil platyrrhines, based on a total evidence data set of 418 morphological characters and 10.2 kilobases of DNA sequence data from 17 nuclear genes taken from previous studies, using undated and tip-dating approaches in a Bayesian framework. We compare the results of these analyses with molecular scaffold analyses using maximum parsimony and Bayesian approaches, and we use a formal information theoretic approach to identify unstable taxa. After a posteriori pruning of unstable taxa, the undated and tip-dating topologies appear congruent with recent molecular analyses and support largely similar relationships, with strong support for Stirtonia as a stem alouattine, Neosaimiri as a stem saimirine, Cebupithecia as a stem pitheciine, and Lagonimico as a stem callitrichid. Both analyses find three Greater Antillean subfossil platyrrhines (Xenothrix, Antillothrix, and Paralouatta) to form a clade that is related to Callicebus, congruent with a single dispersal event by the ancestor of this clade to the Greater Antilles. They also suggest that the fossil Proteropithecia may not be closely related to pitheciines, and that all known platyrrhines older than the Middle Miocene are stem taxa. Notably, the undated analysis found the Early Miocene Panamacebus (currently recognized as the oldest known cebid) to be unstable, and the tip-dating analysis placed it outside crown Platyrrhini. Our tip-dating analysis supports a late Oligocene or earliest Miocene (20.8–27.0 Ma) age for crown Platyrrhini, congruent with recent molecular clock analyses.

A New Humerus of Homunculus patagonicus, a Stem Platyrrhine from the Santa Cruz Formation (Late Early Miocene), Santa Cruz Province, Argentina

We describe a well-preserved humerus of Homunculus patagonicus, a stem platyrrhine from the late early Miocene of the Santa Cruz Formation, Santa Cruz Province, Argentina. The distal part of a humerus was collected by Carlos Ameghino and figured in the 19th Century, but is now lost. Other described postcranial elements, also collected by him include a femur and a partial radius. Comparative observations are made with living and extinct platyrrhines, Oligocene African anthropoids, and extant strepsirrhines. Homunculus patagonicus was a robustly built arboreal quadruped that weighed between 2.2 and 2.6 kg. There is no evidence that the elbow could be fully extended as in living suspensory platyrrhines like Ateles. The medial orientation of the epicondyle suggests that the finger and wrist flexors were not aligned with the long axis of the limb, a distinction from more cursorial monkeys (extant cercopithecoids and the Cuban Pleistocene fossil platyrrhine Paralouatta have retroflexed medial epicondyles). Overall, the morphology is typically platyrrhine although the bone is quite robust. The robustness of the humerus is most comparable to that of early anthropoids from Africa rather than any extant platyrrhine.

Morphological variation and covariation in mandibular molars of platyrrhine primates.

Molars are highly integrated biological structures that have been used for inferring evolutionary relationships among taxa. However, parallel and convergent morphological traits can be affected by developmental and functional constraints. Here, we analyze molar shapes of platyrrhines in order to explore if platyrrhine molar diversity reflects homogeneous patterns of molar variation and covariation. We digitized 30 landmarks on mandibular first and second molars of 418 extant and 11 fossil platyrrhine specimens to determine the degree of integration of both molars when treated as a single module. We combined morphological and phylogenetic data to investigate the phylogenetic signal and to visualize the history of molar shape changes. All platyrrhine taxa show a common shape pattern suggesting that a relatively low degree of phenotypic variation is caused by convergent evolution, although molar shape carries significant phylogenetic signal. Atelidae and Pitheciidae show high levels of integration with low variation between the two molars, whereas the Cebinae/Saimiriinae, and especially Callitrichinae, show greater variation between molars and trend toward a modular organization. We hypothesize that biomechanical constraints of the masticatory apparatus, and the dietary profile of each taxon are the main factors that determine high covariation in molars. In contrast, low molar shape covariation may result from the fact that each molar exhibits a distinct ecological signal, as molars can be exposed to distinct occlusal loadings during food processing, suggesting that different selective pressures on molars can reduce overall molar integration.

Previously unknown fossil platyrrhines (Primates) of Patagonia from the Tournouër collection at the Muséum national d'Histoire naturelle, Paris

Three unpublished fossil primate specimens from Patagonia (Argentina) are reported here. They are part of the Tournouër collection housed at the Muséum national d'Histoire naturelle in Paris, France, and correspond to a partial mandible collected in 1902, and one upper deciduous premolar and one upper permanent molar collected in 1899. The partial mandible comes from the early Miocene sediments in the Coyle river area (Santa Cruz Province, Argentina), and is attributable to Homunculus patagonicusAmeghino, 1891. It adds to the several specimens assigned to Homunculus patagonicus that were collected since the times of the Ameghino brothers in the area, between the rivers Coyle and Gallegos. Two other dental specimens came from Colhue-Huapi (Chubut province, Argentina). Both are here assigned to Mazzonicebus almendraeKay, 2010, the only known fossil primate in the early Miocene levels of Gran Barranca, in the Colhue-Huapi area. This contribution provides new morphological information concerning the mandible and dentition of HomunculusAmeghino, 1891, and the first evidence of the deciduous dentition of MazzonicebusKay, 2010.

The evolution of the platyrrhine talus: A comparative analysis of the phenetic affinities of the Miocene platyrrhines with their modern relatives

Platyrrhines are a diverse group of primates that presently occupy a broad range of tropical-equatorial environments in the Americas. However, most of the fossil platyrrhine species of the early Miocene have been found at middle and high latitudes. Although the fossil record of New World monkeys has improved considerably over the past several years, it is still difficult to trace the origin of major modern clades. One of the most commonly preserved anatomical structures of early platyrrhines is the talus. This work provides an analysis of the phenetic affinities of extant platyrrhine tali and their Miocene counterparts through geometric morphometrics and a series of phylogenetic comparative analyses. Geometric morphometrics was used to quantify talar shape affinities, while locomotor mode percentages (LMPs) were used to test if talar shape is associated with locomotion. Comparative analyses were used to test if there was convergence in talar morphology, as well as different models that could explain the evolution of talar shape and size in platyrrhines. Body mass predictions for the fossil sample were also computed using the available articular surfaces. The results showed that most analyzed fossils exhibit a generalized morphology that is similar to some ‘generalist’ modern species. It was found that talar shape covaries with LMPs, thus allowing the inference of locomotion from talar morphology. The results further suggest that talar shape diversification can be explained by invoking a model of shifts in adaptive peak to three optima representing a phylogenetic hypothesis in which each platyrrhine family occupied a separate adaptive peak. The analyses indicate that platyrrhine talar centroid size diversification was characterized by an early differentiation related to a multidimensional niche model. Finally, the ancestral platyrrhine condition was reconstructed as a medium-sized, generalized, arboreal, quadruped.

Evolutionary Significance of the Entepicondylar Foramen of the Humerus in New World Monkeys (Platyrrhini)

Although consistently absent in extant catarrhine monkeys, the presence and absence of the entepicondylar foramen of the humerus (EEF) vary greatly among living and fossil platyrrhines. Aiming to test the mode of evolution of this character in platyrrhine phylogeny, we performed stochastic character mapping of the presence and absence of the EEF based on museum material and literature research. We also tested for phylogenetic signal of the EEF and its correlation with semi-brachation, vertical clinging, and manipulative foraging in New World monkeys. We found more losses than gains of the EEF in the Haplorhini and Platyrrhini phylogenies. The EEF showed a strong phylogenetic signal congruent with a Brownian model of evolution. All models that assumed a dependence between foraging and locomotion behaviors showed a better fit to the data, but the differences from an independent model were not statistically significant. Thus, we assume that the observed pattern could have originated from genetic drift, except in Leontopithecus where the EEF appears to have been lost due to the narrowing of the distal humerus. Although not functionally relevant, the presence and absence of EEF is taxonomically useful for discriminating between the Aotus and Callicebus species groups, and diagnoses large platyrrhine clades such as marmosets and Atelidae. Thus, it should be considered when inferring systematic relationships among living and extinct platyrrhines.

Morphometric variation of extant platyrrhine molars: taxonomic implications for fossil platyrrhines

The phylogenetic position of many fossil platyrrhines with respect to extant ones is not yet clear. Two main hypotheses have been proposed: the layered or successive radiations hypothesis suggests that Patagonian fossils are Middle Miocene stem platyrrhines lacking modern descendants, whereas the long lineage hypothesis argues for an evolutionary continuity of all fossil platyrrhines with the extant ones. Our geometric morphometric analysis of a 15 landmark-based configuration of platyrrhines’ first and second lower molars suggest that morphological stasis may explain the reduced molar shape variation observed. Platyrrhine lower molar shape might be a primitive retention of the ancestral state affected by strong ecological constraints throughout the radiation of the main platyrrhine families. The Patagonian fossil specimens showed two distinct morphological patterns of lower molars, Callicebus—like and Saguinus—like, which might be the precursors of the extant forms, whereas the Middle Miocene specimens, though showing morphological resemblances with the Patagonian fossils, also displayed new, derived molar patterns, Alouatta—like and Pitheciinae—like, thereby suggesting that despite the overall morphological stasis of molars, phenotypic diversification of molar shape was already settled during the Middle Miocene.

New endemic platyrrhine humerus from Haiti and the evolution of the Greater Antillean platyrrhines

Much debate surrounds the phylogenetic affinities of the endemic Greater Antillean platyrrhines. Thus far, most phylogenetic analyses have been constructed and tested using craniodental characters. We add to this dialog by considering how features of the distal humerus support or refute existing hypotheses for the origins of fossil Caribbean primates, utilizing three-dimensional geometric morphometric data in combination with character based cladistic analyses. We also add to the sample of fossil platyrrhine humeri with the description of UF 114718, a new distal humerus from Haiti.We reconstruct UF 114718 to be a generalized, arboreal quadruped attributed to the species Insulacebus toussantiana. Our results from phylogenetic analyses lend some support to the idea that some Greater Antillean fossil taxa including Xenothrix mcgregori, Antillothrix bernensis, and Insulacebus toussaintiana could form a monophyletic clade that is sister to either extant Platyrrhini or basal pitheciids. Based on the distal humeral data, we reconstruct the earliest ancestral platyrrhine to be a generalized, arboreal quadruped that potentially emphasized pronated arm postures during locomotion and may have engaged in some limited climbing, most similar in shape to early anthropoids and some of the earliest Antillean forms. However, aspects of shape and standard qualitative characters relating to the distal humerus seem to be variable and prone to both homoplasy and reversals; thus these results must be interpreted cautiously and (where possible) within the context provided by other parts of the skeleton.

Oldest known cranium of a juvenile New World monkey (Early Miocene, Patagonia, Argentina): Implications for the taxonomy and the molar eruption pattern of early platyrrhines

A juvenile cranium of Homunculus patagonicus Ameghino, 1891a from the late Early Miocene of Santa Cruz Province (Argentina) provides the first evidence of developing cranial anatomy for any fossil platyrrhine. The specimen preserves the rostral part of the cranium with deciduous and permanent alveoli and teeth. The dental eruption sequence in the new specimen and a reassessment of eruption patterns in living and fossil platyrrhines suggest that the ancestral platyrrhine pattern of tooth replacement was for the permanent incisors to erupt before M1, not an accelerated molar eruption (before the incisors) as recently proposed.Two genera and species of Santacrucian monkeys are now generally recognized: H. patagonicus Ameghino, 1891a and Killikaike blakei Tejedor et al., 2006. Taxonomic allocation of Santacrucian monkeys to these species encounters two obstacles: 1) the (now lost) holotype and a recently proposed neotype of H. patagonicus are mandibles from different localities and different geologic members of the Santa Cruz Formation, separated by approximately 0.7 million years, whereas the holotype of K. blakei is a rostral part of a cranium without a mandible; 2) no Santacrucian monkey with associated cranium and mandible has ever been found. Bearing in mind these uncertainties, our examination of the new specimen as well as other cranial specimens of Santacrucian monkeys establishes the overall dental and cranial similarity between the holotype of Killikaike blakei, adult cranial material previously referred to H. patagonicus, and the new juvenile specimen. This leads us to conclude that Killikaike blakei is a junior subjective synonym of H. patagonicus.

Biogeography in deep time – What do phylogenetics, geology, and paleoclimate tell us about early platyrrhine evolution?

Molecular data have converged on a consensus about the genus-level phylogeny of extant platyrrhine monkeys, but for most extinct taxa and certainly for those older than the Pleistocene we must rely upon morphological evidence from fossils. This raises the question as to how well anatomical data mirror molecular phylogenies and how best to deal with discrepancies between the molecular and morphological data as we seek to extend our phylogenies to the placement of fossil taxa.Here I present parsimony-based phylogenetic analyses of extant and fossil platyrrhines based on an anatomical dataset of 399 dental characters and osteological features of the cranium and postcranium. I sample 16 extant taxa (one from each platyrrhine genus) and 20 extinct taxa of platyrrhines. The tree structure is constrained with a “molecular scaffold” of extant species as implemented in maximum parsimony using PAUP with the molecular-based ‘backbone’ approach. The data set encompasses most of the known extinct species of platyrrhines, ranging in age from latest Oligocene (∼26Ma) to the Recent. The tree is rooted with extant catarrhines, and Late Eocene and Early Oligocene African anthropoids.Among the more interesting patterns to emerge are: (1) known early platyrrhines from the Late Oligocene through Early Miocene (26–16.5Ma) represent only stem platyrrhine taxa; (2) representatives of the three living platyrrhine families first occur between 15.7Ma and 13.5Ma; and (3) recently extinct primates from the Greater Antilles (Cuba, Jamaica, Hispaniola) are sister to the clade of extant platyrrhines and may have diverged in the Early Miocene. It is probable that the crown platyrrhine clade did not originate before about 20–24Ma, a conclusion consistent with the phylogenetic analysis of fossil taxa presented here and with recent molecular clock estimates.The following biogeographic scenario is consistent with the phylogenetic findings and climatic and geologic evidence: Tropical South America has been a center for platyrrhine diversification since platyrrhines arrived on the continent in the middle Cenozoic. Platyrrhines dispersed from tropical South America to Patagonia at ∼25–24Ma via a “Paraná Portal” through eastern South America across a retreating Paranense Sea. Phylogenetic bracketing suggests Antillean primates arrived via a sweepstakes route or island chain from northern South America in the Early Miocene, not via a proposed land bridge or island chain (GAARlandia) in the Early Oligocene (∼34Ma). Patagonian and Antillean platyrrhines went extinct without leaving living descendants, the former at the end of the Early Miocene and the latter within the past six thousand years. Molecular evidence suggests crown platyrrhines arrived in Central America by crossing an intermittent connection through the Isthmus of Panama at or after 3.5Ma. Any more ancient Central American primates, should they be discovered, are unlikely to have given rise to the extant Central American taxa in situ.

Locomotor Diversification in New World Monkeys: Running, Climbing, or Clawing Along Evolutionary Branches

Modern platyrrhines exhibit a remarkable diversity of locomotor and postural adaptations, which evolved along multiple trajectories since the initial immigration to the island continent of South America. We trace this diversification by reviewing the available paleontological and neontological data for postcranial morphology and ecological adaptation. Fossil platyrrhines are notably diverse, from the Oligocene Branisella, to the varied Patagonian early Miocene quadurpedal-leaping and quadrupedal-climbing fossils of disputed affinities, on through the rich middle Miocene Colombian quadurpedal-leaping forms. More recent taxa exhibit even more derived positional patterns, from the largest suspensory atelids in Pleistocene Brazil, to the remarkable Antillean radiation with suspensory forms and also semiterrestrial species, with postcranial morphology convergent on some Old World monkeys. Field studies of positional behavior of modern platyrrhines set the framework for a spectrum of locomotor adaptations. Central within this spectrum is a cluster of medium-sized species with generalized locomotion (quadrupedal-leaping). At opposite poles lie the more derived conditions: large-bodied species exhibiting locomotor specializations for climbing-suspension; small-bodied species exhibiting adaptations for claw climbing and leaping. This behavior-based spectrum of locomotor diversification is similarly evident in a morphology-based pattern, that is, that produced by the shape of the talus. The implications of the record of platyrrhine postcranial evolution for the competing hypotheses of platyrrhine phylogenetic patterns, the "long lineage hypothesis" and the "stem platyrrhine hypothesis," are considered.

Paleodiet of Extinct Platyrrhines With Emphasis on the Caribbean Forms: Three‐Dimensional Geometric Morphometrics of Mandibular Second Molars

A three-dimensional geometric morphometric approach was employed to examine shape variation in laser-scan generated models of lower second molars and its relationship to diet in a sample of 9 extant and 16 extinct platyrrhine genera. Principal component analysis of twenty-three x,y,z landmarks describing the occlusal table and sidewalls showed that dental relief was the main contributing factor to variation along the first axis. Discriminant function analysis (DFA) of PC 1 scores and centroid size accurately classified extant platyrrhines according to dietary preference; however, without centroid size, the DFA was less successful. Within this framework, most of the fossil platyrrhines, including specimens from Patagonia, Colombia, Brazil, and the Caribbean, were predicted to have had a frugivorous diet, but several taxa were classified as having a frugivorous/insectivorous diet, the middle Miocene Neosaimiri, Patasola, and Laventiana, all from La Venta. Alouattins, including the La Ventan Stirtonia and the Cuban Paralouatta, showed variable classification as either frugivores or folivore/frugivores. Xenothrix, from Jamaica, was classified either as a frugivore or frugivore/omnivore. Dietary profiles across different extinct platyrrhine communities are compared and discussed in a paleoecological context.

Evolutionary Morphology, Platyrrhine Evolution, and Systematics

This special volume of the Anatomical Record focuses on the evolutionary morphology of New World monkeys. The studies range from three-dimensional surface geometry of teeth to enamel ultrastructure; from cranioskeletal adaptations for eating leaves and seeds to the histology of taste bud proxies; from the architecture of its bones to the mechanoreceptors of the tail's skin; from the physical properties of wild foods to the feeding biomechanics of jaws and skull; from the shapes of claws and fingertips, and of elbows, to the diversity and morphology of positional behavior; from the vomeronasal organ and its biological roles to links between brains, guts, sociality, and feeding; from the gum-eating adaptations of the smallest platyrrhines to the methods used to infer how big the largest fossil platyrrhines were. They demonstrate the power of combining functional morphology, behavior, and phylogenetic thinking as an approach toward reconstructing the evolutionary history of platyrrhine primates. While contributing new findings pertaining to all the major clades and ecological guilds, these articles reinforce the view that platyrrhines are a coherent ecophylogenetic array that differentiated along niche dimensions definable principally by body size, positional behavior, and feeding strategies. In underlining the value of character analysis and derived morphological and behavioral patterns as tools for deciphering phylogenetic and adaptational history, doubts are raised about a competing small-bore morphological method, parsimony-based cladistic studies. Intentionally designed not to enlist the rich reservoir of platyrrhine evolutionary morphology, an empirical assessment of the costs incurred by this research stratagem reveals inconsistent, nonrepeatable, and often conflicting results.

First skull of Antillothrix bernensis, an extinct relict monkey from the Dominican Republic.

The nearly pristine remains of Antillothrix bernensis, a capuchin-sized (Cebus) extinct platyrrhine from the Dominican Republic, have been found submerged in an underwater cave. This represents the first specimen of an extinct Caribbean primate with diagnostic craniodental and skeletal parts in association, only the second example of a skull from the region, and one of the most complete specimens of a fossil platyrrhine cranium yet discovered. Cranially, it closely resembles living cebines but is more conservative. Dentally, it is less bunodont and more primitive than Cebus, with crowns resembling Saimiri (squirrel monkeys) and one of the oldest definitive cebines, the late Early Miocene Killikaike blakei from Argentina. The tricuspid second molar also resembles the enigmatic marmosets and tamarins, whose origins continue to present a major gap in knowledge of primate evolution. While the femur is oddly short and stout, the ulna, though more robust, compares well with Cebus. As a member of the cebid clade, Antillothrix demonstrates that insular Caribbean monkeys are not monophyletically related and may not be the product of a single colonizing event. Antillothrix bernensis is an intriguing mosaic whose primitive characters are consistent with an early origin, possibly antedating the assembly of the modern primate fauna in greater Amazonia during the La Venta horizon. While most Greater Antillean primate specimens are quite young geologically, this vanished radiation, known from Cuba (Paralouatta) and Jamaica (Xenothrix) as well as Hispaniola, appears to be composed of long-lived lineages like several other mainland clades.

Estimating body mass in New World “monkeys” (Platyrrhini, Primates), with a consideration of the Miocene platyrrhine, Chilecebus carrascoensis

Well-constrained estimates of adult body mass for species of fossil platyrrhines (New World “monkeys”) are essential for resolving numerous paleobiological questions. However, no consensus exists as to which craniodental measures best correlate with body mass among extant taxa in this clade. In this analysis, we analyze 80 craniodental variables and generate predictive equations applicable to fossil taxa, including the early platyrrhine Chilecebus carrascoensis.We find mandibular length to be the best craniodental predictor of body mass. There is no significant difference in predictive value between osteological and dental measures. Variables associated with the mandible and lower dentition do significantly outperform the cranium and upper dentition. Additionally, we demonstrate that modern platyrrhines differ, morphometrically, from early fossil forms. Chilecebus possesses unusual cranial proportions in several key features, as well as proportionally narrow upper incisors and wide upper cheek teeth. These variables yield widely divergent body mass estimates for Chilecebus, implying that the correlations observed in a crown group cannot be assumed a priori for early diverging fossils. Variables allometrically consistent with those in extant forms yield a body mass estimate of slightly less than 600 grams for Chilecebus, nearly a factor of two smaller than prior preliminary estimates.Scaled to body mass, the brain of Chilecebus is markedly smaller than those of modern anthropoids, despite its lowered body mass estimate advocated here. This finding, in conjunction with a similar pattern exhibited by fossil catarrhines, suggests that increased encephalization arose independently in the two extant subgroups of anthropoids (platyrrhines and catarrhines).

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).

新世界ザルにおける下顎大臼歯から推測する上顎大臼歯の形態‐ｗｅａｒ ｆａｃｅｔ８とｈｙｐｏｃｏｎｅの関係について‐

The upper molars carry a good amount of information for identifying the fossil Platyrrhines, whereas the lower molars do not. However, the upper molars are not found so much as the lower molars. It is supposed that the occlusal feature of an upper molar is inferred from the occlusal morphology of the respective lower molar. It is hypothesized that wear facet 8 is indicative of the hypocone, as it is formed in the distal part of entocristid of a lower molar by the occlusion with hypocone which is important trait classifying Callitrichine from other Platyrrhines. However, the development of lingual cingulum may give confounding effect on the development of facet 8. In this study, using specimens of Saimiri (hypocone present), Callithrix (hypocone absent) and Saguinus(hypocone partially present), which had different degree of occlusal wearing, I observed both of the upper and lower first molars for the presence both of the wear facet 8 and hypocone under binocular microscopes. As a result, the formation of lower facet 8 was found to be strictly indicative of the hypocone without being influenced by the lingual cingulum. Application of this relationship on such Platyrrhine fossils as Aotus dindensis, Mohanamico hershkovitzi, Patasola magdalena, Xenothrix mcgregori, Nuciruptor rubricae, whose upper molars were not found, and therefore, which have not been properly classified, gave phylogenetic implications.

New primate genus from the Miocene of Argentina

Killikaike blakei is a new genus and species of anthropoid from the late Early Miocene of southeastern Argentina based on the most pristine fossil platyrrhine skull and dentition known so far. It is part of the New World platyrrhine clade (Family Cebidae; Subfamily Cebinae) including modern squirrel (Saimiri) and capuchin monkeys (Cebus) and their fossil relatives known from Early to Middle Miocene and subrecent periods. Living cebines are relatively large-brained, adroit predatory foragers and live within complex social groups, and wild capuchins exhibit a wide range of behaviors associated with enhanced intelligence. We show that K. blakei lacks diagnostic derived characteristics of the lower face and premolar dentition that are shared by modern cebines, but its strongly vaulted frontal bone and capacious anterior cranial fossa indicate the early evolution of an enlarged forebrain.

New fossil materials of the earliest new world monkey, Branisella boliviana, and the problem of platyrrhine origins

Branisella boliviana, from the Late Oligocene of Salla, Bolivia, is the oldest fossil platyrrhine monkey discovered. To date, several fossil specimens of Branisella have been obtained, but most of them are fragmentary dentitions, so the animals craniodental morphology is still obscure. During the 1996 field season a pair of upper and lower jaw fragments and another nearly complete mandible were recovered. These new fossil materials reveal the following morphological features in Branisella: 1) P2 is much smaller than P3,4, whereas P2 is relatively small but probably sexually dimorphic; 2) the zygomatic arch protrudes smoothly posterolaterally from the maxillary bone, as in extant Callicebus; 3) the mandibular arcade is nearly V-shaped and the symphysial angle, which is formed by the horizontal plane and the anterior face of mandibular symphysis, is about 40°, i.e., it neither leans as far anteriorly as in callitrichines nor does it stand as vertically as Cebus; 4) upper and lower molars wore down rapidly in life, suggesting a herbivorous diet and the possibility of terrestriality; and 5) dental eruptive sequence is the same as in extant Aotus. As a whole, the dentition of Branisella is very similar to that of Proteopithecus from the Late Eocene of Fayum, Egypt, except in the lower canine morphology, suggesting a close phyletic relationship between them. The origin and early diversification of platyrrhine monkeys might have occurred on the African continent before crossing the Atlantic Ocean. Am J Phys Anthropol 111:263–281, 2000. © 2000 Wiley-Liss, Inc.

New fossil materials of the earliest new world monkey, Branisella boliviana, and the problem of platyrrhine origins.

Branisella boliviana, from the Late Oligocene of Salla, Bolivia, is the oldest fossil platyrrhine monkey discovered. To date, several fossil specimens of Branisella have been obtained, but most of them are fragmentary dentitions, so the animals craniodental morphology is still obscure. During the 1996 field season a pair of upper and lower jaw fragments and another nearly complete mandible were recovered. These new fossil materials reveal the following morphological features in Branisella: 1) P(2) is much smaller than P(3,4), whereas P(2) is relatively small but probably sexually dimorphic; 2) the zygomatic arch protrudes smoothly posterolaterally from the maxillary bone, as in extant Callicebus; 3) the mandibular arcade is nearly V-shaped and the symphysial angle, which is formed by the horizontal plane and the anterior face of mandibular symphysis, is about 40 degrees, i.e., it neither leans as far anteriorly as in callitrichines nor does it stand as vertically as Cebus; 4) upper and lower molars wore down rapidly in life, suggesting a herbivorous diet and the possibility of terrestriality; and 5) dental eruptive sequence is the same as in extant Aotus. As a whole, the dentition of Branisella is very similar to that of Proteopithecus from the Late Eocene of Fayum, Egypt, except in the lower canine morphology, suggesting a close phyletic relationship between them. The origin and early diversification of platyrrhine monkeys might have occurred on the African continent before crossing the Atlantic Ocean.