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.

Unique nasal turbinal morphology reveals Homunculus patagonicus functionally converged on modern platyrrhine olfactory sensitivity.

The phyletic position of early Miocene platyrrhine Homunculus patagonicus is currently a matter of debate. Some regard it to be an early member of the Pitheciidae, represented today by the sakis, uakaris, and titi monkeys. Others view Homunculus as a stem platyrrhine, part of a group that diversified in Patagonia and converged in some respects on modern pitheciine dental and gnathic morphology and perhaps seed-eating specialization. New details of its internal nasal anatomy are pertinent to resolving this debate. In addition, they provide a new perspective on how modern platyrrhine olfactory sensitivity evolved. Here we reconstruct the internal nasal anatomy of Homunculus from high-resolution computed tomography scans. This species has three ethmoturbinals, the scrolls of bone in the nasal fossa that were covered in sensory epithelium in vivo. This condition stands in stark contrast to extant platyrrhines, and indeed to all other haplorhines, which have only two ethmoturbinals or, in the case of all pitheciid platyrrhines, only one ethmoturbinal. Quantitatively, however, Homunculus has an olfactory turbinal surface area that falls within the modern platyrrhine distribution, suggesting that while turbinal numbers differ, olfactory sensitivity in this taxon was likely comparable to that of modern platyrrhines. These new data from the fossil record provide further support for the hypothesis that Homunculus is a stem platyrrhine that functionally converged on modern platyrrhines rather than being an early representative of any extant clade.

The Stabilizing Function of the Tail During Arboreal Quadrupedalism.

Locomotion on the narrow and compliant supports of the arboreal environment is inherently precarious. Previous studies have identified a host of morphological and behavioral specializations in arboreal animals broadly thought to promote stability when on precarious substrates. Less well-studied is the role of the tail in maintaining balance. However, prior anatomical studies have found that arboreal taxa frequently have longer tails for their body size than their terrestrial counterparts, and prior laboratory studies of tail kinematics and the effects of tail reduction in focal taxa have broadly supported the hypothesis that the tail is functionally important for maintaining balance on narrow and mobile substrates. In this set of studies, we extend this work in two ways. First, we used a laboratory dataset on three-dimensional segmental kinematics and tail inertial properties in squirrel monkeys (Saimiri boliviensis) to investigate how tail angular momentum is modulated during steady-state locomotion on narrow supports. In the second study, we used a quantitative dataset on quadrupedal locomotion in wild platyrrhine monkeys to investigate how free-ranging arboreal animals adjust tail movements in response to substrate variation, focusing on kinematic measures validated in prior laboratory studies of tail mechanics (including the laboratory data presented). Our laboratory results show that S. boliviensis significantly increase average tail angular momentum magnitudes and amplitudes on narrow supports, and primarily regulate that momentum by adjusting the linear and angular velocity of the tail (rather than via changes in tail posture per se). We build on these findings in our second study by showing that wild platyrrhines responded to the precarity of narrow and mobile substrates by extending the tail and exaggerating tail displacements, providing ecological validity to the laboratory studies of tail mechanics presented here and elsewhere. In conclusion, our data support the hypothesis that the long and mobile tails of arboreal animals serve a biological role of enhancing stability when moving quadrupedally over narrow and mobile substrates. Tail angular momentum could be used to cancel out the angular momentum generated by other parts of the body during steady-state locomotion, thereby reducing whole-body angular momentum and promoting stability, and could also be used to mitigate the effects of destabilizing torques about the support should the animals encounter large, unexpected perturbations. Overall, these studies suggest that long and mobile tails should be considered among the fundamental suite of adaptations promoting safe and efficient arboreal locomotion.

Muscle-tendon arrangement and innervation pattern of the m. flexor digitorum superficialis in the common marmoset (Callithrix jacchus), squirrel monkey (Saimiri sciureus) and spider monkey (Ateles sp.).

The muscle-tendon arrangement of the m. flexor digitorum superficialis (FDS) varies among different primate groups. Recent developmental investigations revealed that the primordium of FDS emerges in the hand region first and relocates to the forearm later. The relationship between the diverse muscle-tendon arrangement and the characteristic developmental process of FDS is important for understanding the evolutionary changes of the FDS. Moreover, the innervation pattern cannot go unremarked when discussing the muscle homology and evolution. We examined the muscle-tendon arrangement and intramuscular nerve distribution of the FDS in three genera of Platyrrhini: three common marmosets (Callithrix jacchus), two squirrel monkeys (Saimiri sciureus) and two spider monkeys (Ateles sp.). We observed that the FDS consisted of multiple muscle bellies. The origin of the muscle bellies to digits II and V varied, whereas muscle bellies to digits III and IV consistently originated from the medial epicondyle. The muscle-tendon arrangement of the FDS differed among the three genera owing to the different origins of muscle bellies to digits II and V. In all the examined specimens, the muscle bellies to digits II and/or III were innervated by the direct nerve branches from the median nerve. However, the muscle bellies to digits IV and V never received direct nerve branches from the median nerve. Nerve branches within the belly to digit III extended into the belly to digit IV, and one nerve branch within the belly to digit IV extended into the belly to digit V. These consistent nerve distribution patterns suggest that different patterns of FDS muscle-tendon arrangement have changed from that of a common ancestral condition. It is plausible that the diverse origins of muscle bellies in the FDS are attributable to the difference in the destination for the relocation of the muscle bellies during developmental processes.

Parvimico materdei gen. et sp. nov.: A new platyrrhine from the Early Miocene of the Amazon Basin, Peru.

Three field seasons of exploration along the Río Alto Madre de Dios in Peruvian Amazonia have yielded a fauna of micromammals from a new locality AMD-45, at ∼12.8°S. So far we have identified the new primate described here as well as small caviomorph rodents, cenolestoid marsupials, interatheriid notoungulates, xenarthrans, fish, lizards and invertebrates. The site is in the Bala Formation as exposed where the river transects a syncline. U-Pb dates on detrital zircons constrain the locality's age at between 17.1 ± 0.7 Ma and 18.9 ± 0.7 Ma, making the fauna age-equivalent to that from the Pinturas Formation and the older parts of the Santa Cruz Formation of Patagonian Argentina (Santacrucian). The primate specimen is an unworn M1 of exceptionally small size (equivalent in size to the extant callitrichine, Callithrix jacchus, among the smallest living platyrrhines and the smallest Eocene-Early Miocene platyrrhine yet recorded). Despite its small size it is unlike extant callitrichines in having a prominent cingulum hypocone. Based on the moderate development of the buccal crests, this animal likely had a diet similar to that of frugivorous callitrichines, and distinctly different from the more similarly-sized gummivores, Cebuella and C. jacchus. The phyletic position of the new taxon is uncertain, especially given the autapomorphic character of the tooth as a whole. Nevertheless, its unusual morphology hints at a wholly original and hitherto unknown Amazonian fauna, and reinforces the impression of the geographic separation of the Amazonian tropics from the more geographically isolated southerly parts of the continent in Early Miocene times.

My branch is your branch: Talar morphology correlates with relative substrate size in platyrrhines at Tiputini Biodiversity Station, Ecuador.

Given that most species of primates are predominantly arboreal, maintaining the ability to move among branches of varying sizes has presumably been a common selective force in primate evolution. However, empirical evaluations of the relationships between morphological variation and characteristics of substrate geometry, such as substrate diameter relative to an animal's body mass, have been limited by the lack of quantified substrate usage in the wild. Here we use recently published quantitative data to assess the relationships between relative substrate size and talar morphology in nine New World monkey species at the Tiputini Biodiversity Station, Ecuador. Within this sample, both fibular facet angle (the angle between the fibular facet and the trochlear rims) and body-mass-standardized area of the medial tibial facet decrease as average and maximum relative substrate size increases. Correlations between medial tibial facet area and relative substrate size are driven by the inclusion of callitrichids in this sample. Nevertheless, these findings strengthen the hypothesis that variation in fibular facet orientation and medial tibial facet area are functionally correlated with habitual degrees of pedal inversion. They also strengthen the notion that evolutionarily changing body mass could impact habitat geometry experienced by a lineage and thereby substantially impact major trends in primate morphological evolution. This study highlights the importance of empirical data on substrate use in living primates for inferring functional and evolutionary implications of morphological variation.

Ambient occlusion and PCV (portion de ciel visible): A new dental topographic metric and proxy of morphological wear resistance.

Recently, ambient occlusion, quantified through portion de ciel visible (PCV) was introduced as a method for quantifying dental morphological wear resistance and reconstructing diet in mammals. Despite being used to reconstruct diet and investigate the relationship between dental form and function, no rigorous analysis has investigated the correlation between PCV and diet. Using a sample of platyrrhine and prosimians M2s, we show average PCV was significantly different between most dietary groups. In prosimian, insectivores had the lowest PCV, followed by folivores, omnivores, frugivores, and finally hard-object feeders. In platyrrhines, omnivores had the lowest average PCV, followed by folivores, frugivores, and finally hard-object feeders. PCV was correlated to two topographic variables (Dirichlet normal energy, DNE, and relief index, RFI) but uncorrelated to three others (orientation patch count rotated, OPCR, tooth surface area, and tooth size). The OPCR values here differed greatly from previously published values using the same sample, showing how differences in data acquisition (i.e., using 2.5D vs. 3D surfaces) can lead to drastic differences in results. Compared to other popular topographic variables, PCV performed as well or better at predicting diet in these groups, and when combined with a metric for size, the percent of successful dietary classifications reached 90%. Further, using an ontogenetic series of hominin (Paranthropus robustus) M2s, we show that PCV correlates well with probability of wear, with PCV values being higher on the portions of the occlusal surface that experience more wear (e.g., cusps and crest tips, wear facets) than the portions of the tooth that experience less. This relationship is strongest once wear facets have begun to form on the occlusal surface. These results highlight the usefulness of PCV in quantifying morphological wear resistance and predicting diet in mammals.

Investigating the effect of endocranial volume on cranial shape in platyrrhines and the relevance of this relationship to interpretations of the fossil record.

OBJECTIVES: Fossils have been linked to Alouatta based on shared cranial morphology and small brain size. However, the relationship between endocranial volume and cranial shape is unclear; it is possible that any platyrrhine with a small brain may exhibit "Alouatta-like" features due to being "de-encephalized." We test two hypotheses: (a) there are aspects of cranial shape related to encephalization common to all platyrrhines; (b) it is these cranial traits that unite the small-brained "Alouatta-like" fossils. MATERIALS AND METHODS: Three-dimensional cranial shape and endocranial volume (ECV) were measured on 350+ extant platyrrhine crania, Cartelles, Paralouatta, and Antillothrix. Encephalization quotient (EQ) was calculated using regressions of ECV on cranial centroid size. Multivariate regressions were performed using the shape coordinates and EQ and shape changes associated with EQ were visualized. Cranial shape was predicted for a hypothetical primate with an EQ matching the fossils and this shape was compared to the Alouatta mean. RESULTS: There is a significant proportion of cranial shape variation explained by EQ in some taxa. The aspects of shape that are correlated with EQ are shared by several taxa and some have parallel regression vectors, but there is no overall pattern of shape change common to all platyrrhines. However, all taxa look more similar to Alouatta when their EQ is decreased, particularly Pithecia. DISCUSSION: Given that a decrease in encephalization can cause a more Alouatta-like cranial shape in many extant platyrrhines, it should not be automatically assumed that Alouatta-like cranial traits in a small-brained fossil are evidence of a phylogenetic link to the alouattin clade.

A New Tool for Digital Alignment in Virtual Anthropology.

The study of the fossil record is fundamental to understand the evolution of traits. Because fossil remains are often fragmented and/or deformed by taphonomic processes, a preliminary realignment of their constituent parts is often necessary to properly interpret their shapes. In virtual anthropology, these procedures are carried out using digital models of the remains. We present a new semi-automatic alignment R software, Digital Tool for Alignment (DTA), which uses the shape information contained in a reference sample to find the best alignment solution for the disarticulated regions. We tested DTA on three different case-studies: (1) a sample of 14 primate species including both male and female individuals, (2) a simulated, disarticulated skull of Homo sapiens, and (3) a real disarticulated human fossil specimen, Amud 1 (Homo neanderthalensis). In the first case study, we simulated disarticulation directly on digital models of the primate skulls and tested alignment quality as a function of phylogenetic proximity, sex, and body size. In the second, we compared DTA to manual alignments conducted for the same digital models. Finally, we performed DTA on a real-world case study. We found that phylogenetic proximity provides is the most important factor for alignment efficiency. However, sex and allometric effects might also be important and should therefore be taken into account at selecting reference models for alignments. DTA performs at least as well as manual alignments. Yet, as compared to manual procedures, it is faster, requires no prior anatomical knowledge and expertise and allows indefinite manipulation of the fossil items. Anat Rec, 302:1104-1115, 2019. © 2019 Wiley Periodicals, Inc.

Technical note: Comparing dental topography software using platyrrhine molars.

OBJECTIVES: There remain many idiosyncrasies among the values calculated for varying dental topography metrics arising from differences in software preferences among research groups. The aim of this work is to compare and provide potential conversion formulae for dental topography metrics calculated using differing software platforms. METHODS: Three software packages: ArcGIS, Surfer Manipulator, and molaR were used to calculate orientation patch count rotated (OPCR), Dirichlet normal energy (DNE), occlusal relief (OR), slope (m), and angularity (a) on platyrrhine second upper molars. Values derived from the various software packages were compared for distributional consistency and correlation. Where appropriate, formulae for conversion between like measures calculated on different software platforms were developed. RESULTS: When compared with the same measurement across software, OPCR, OR, and slope were all highly correlated. However, only OR demonstrated distributional consistency (i.e., nearly consistent mean, median, max, and min). Slope and OPCR were both higher when calculated by molaR as compared to Surfer Manipulator and ArcGIS calculations, conversion formulae are provided for these measures. DNE is only weakly correlated with angularity; but is correlated with orientation patch count across taxa. DISCUSSION: We explore why there is variation in the dental topography values calculated among the various software packages. The conversion formulae provided in this work will make possible direct comparisons among studies conducted across multiple research groups.

A Penalized Likelihood Framework for High-Dimensional Phylogenetic Comparative Methods and an Application to New-World Monkeys Brain Evolution.

Working with high-dimensional phylogenetic comparative data sets is challenging because likelihood-based multivariate methods suffer from low statistical performances as the number of traits $p $ approaches the number of species $n $ and because some computational complications occur when $p $ exceeds $n$. Alternative phylogenetic comparative methods have recently been proposed to deal with the large $p $ small $n $ scenario but their use and performances are limited. Herein, we develop a penalized likelihood (PL) framework to deal with high-dimensional comparative data sets. We propose various penalizations and methods for selecting the intensity of the penalties. We apply this general framework to the estimation of parameters (the evolutionary trait covariance matrix and parameters of the evolutionary model) and model comparison for the high-dimensional multivariate Brownian motion (BM), Early-burst (EB), Ornstein-Uhlenbeck (OU), and Pagel's lambda models. We show using simulations that our PL approach dramatically improves the estimation of evolutionary trait covariance matrices and model parameters when $p$ approaches $n$, and allows for their accurate estimation when $p$ equals or exceeds $n$. In addition, we show that PL models can be efficiently compared using generalized information criterion (GIC). We implement these methods, as well as the related estimation of ancestral states and the computation of phylogenetic principal component analysis in the R package RPANDA and mvMORPH. Finally, we illustrate the utility of the new proposed framework by evaluating evolutionary models fit, analyzing integration patterns, and reconstructing evolutionary trajectories for a high-dimensional 3D data set of brain shape in the New World monkeys. We find a clear support for an EB model suggesting an early diversification of brain morphology during the ecological radiation of the clade. PL offers an efficient way to deal with high-dimensional multivariate comparative data.

Early Arrival and Climatically-Linked Geographic Expansion of New World Monkeys from Tiny African Ancestors.

New World Monkeys (NWM) (platyrrhines) are one of the most diverse groups of primates, occupying today a wide range of ecosystems in the American tropics and exhibiting large variations in ecology, morphology, and behavior. Although the relationships among the almost 200 living species are relatively well understood, we lack robust estimates of the timing of origin, ancestral morphology, and geographic range evolution of the clade. Herein, we integrate paleontological and molecular evidence to assess the evolutionary dynamics of extinct and extant platyrrhines. We develop novel analytical frameworks to infer the evolution of body mass, changes in latitudinal ranges through time, and species diversification rates using a phylogenetic tree of living and fossil taxa. Our results show that platyrrhines originated 5-10 million years earlier than previously assumed, dating back to the Middle Eocene. The estimated ancestral platyrrhine was small-weighing 0.4 kg-and matched the size of their presumed African ancestors. As the three platyrrhine families diverged, we recover a rapid change in body mass range. During the Miocene Climatic Optimum, fossil diversity peaked and platyrrhines reached their widest latitudinal range, expanding as far South as Patagonia, favored by warm and humid climate and the lower elevation of the Andes. Finally, global cooling and aridification after the middle Miocene triggered a geographic contraction of NWM and increased their extinction rates. These results unveil the full evolutionary trajectory of an iconic and ecologically important radiation of monkeys and showcase the necessity of integrating fossil and molecular data for reliably estimating evolutionary rates and trends.

Normal physiological functions in two animal species with highly different vitamin d status compared to that of humans / Funciones fisiológicas normales en dos especies animales con estatus de vitamina d muy diferentes del actual en seres humanos

Mole rats live in permanent darkness, in networks of underground tunnels (which extend up to 1 km in the subsoil), excavated with their incisors, in warm and semi-arid areas of South Africa. Mole rats have an unusually impoverished vitamin D3 status with undetectable and low plasma concentrations of 25- hydroxyvitamin D3 and 1α,25-dihydroxyvitamin D3, respectively. They express 25-hydroxylase in the liver and 1-hydroxylase and 24-hydroxylase in their kidneys. The presence of specific receptors (VDR) was confirmed in the intestine, kidney, Harderʼs glands and skin. In spite of their poor vitamin D3 status, the apparent fractional intestinal absorption of calcium, magnesium and phosphate was high, always greater than 90%. Oral supplementation with cholecalciferol to mole rats did not improve the efficiency of gastrointestinal absorption of these minerals. Mole ratsdo not display the typical lesion of rickets: hypertrophic and radiolucent growth cartilages. Histological studies reported normal parameters of trabecular and cortical bone quality. Marmosets (monkeys of the New World) are not hypercalcaemic, eventhough they exhibit much higher levels of 25-hydroxyvitamin D3, 1α,25-dihydroxyvitamin D3 and parathyroid hormonethan that of rhesus monkeys and humans. Fed a high vitamin D3 intake (110 IU/day/100 g of body weight), a fraction of the experimental group was found to display osteomalacic changes in their bones: distinct increases in osteoid surface, relative osteoid volume, and active osteoclastic bone resorption. These findings suggest that some marmosets appears to suffer vitamin D-dependent rickets, type II. The maximum binding capacity of the VDR or the dissociation constant of VDR1α,25(OH)2D3 complex of mole rats and New World monkeys are distinctly different of VDR isolated from human cells. Health status of those species appears to be adaptations to the mutations of their VDR. Though rare, as mutations may occur at any time in any patient, the overall message of this review to clinicians may be: recent clinical studies strongly suggests that the normality of physiological functions might be a better indicator of the health status than the serum levels of vitamin D metabolites. (AU)

Las ratas topo viven en la oscuridad permanente, en redes de túneles subterráneos excavadas con sus incisivos (que se extienden hasta 1 km en el subsuelo), en áreas cálidas y semiáridas de Sudáfrica. Las ratas topo tienen un estatus de vitamina D3 inusualmente empobrecido con concentraciones plasmáticas indetectables de 25-hidroxivitamina D3 y bajas de 1α, 25-dihidroxivitamina D3. Poseen 25-hidroxilasa en el hígado y 1-hidroxilasa y 24-hidroxilasa en sus riñones. La presencia de receptores específicos (VDR) ha sido confirmada en el intestino, el riñón, las glándulas de Harder y la piel. A pesar de su pobre estatus de vitamina D3,la absorción fraccional intestinal aparente de calcio, magnesio y fosfato fue alta, siempre superior al 90%. La suplementación oral con colecalciferol a las ratas topo no mejoró la eficacia de la absorción gastrointestinal de estos minerales. No muestran la lesión típica del raquitismo: cartílagos de crecimiento hipertróficos y radiolúcidos. Varios estudios histológicos confirman los hallazgos radiológicos y se informan parámetros normales de la calidad ósea trabecular y cortical. Los titíes (monos del Nuevo Mundo) exhiben calcemias normales con niveles más elevados de 25-hidroxivitamina D3, 1α,25-dihidroxivitamina D3 y hormona paratiroidea que los monos rhesus y los seres humanos. Un tercio de un grupo de titíes alimentados con una alta ingesta de vitamina D3 (110 I/día/100 g de peso corporal) exhibió cambios osteomalácicos en sus huesos: aumento en la superficie osteoide, volumen osteoide y activa reabsorción osteoclástica. Estos hallazgos sugieren que una fracción de la población de titíes padece raquitismo dependiente de vitamina D, tipo II. Debido a mutaciones ocurridas hace millones de años, las máximas capacidades de ligamiento del VDR o los valores de la constante de disociación del complejo VDR-1α,25(OH)2D3 de las ratas topo o monos del Nuevo Mundo son muy diferentes de los verificables en receptores aislados de células humanas actuales. El mensaje de esta revisión a los médicos clínicos podría ser: varios estudios clínicos recientes indican que la normalidad de las funciones fisiológicas de un paciente es un mejor indicador de su salud que los niveles séricos de los metabolitos de la vitamina D. (AU)

Multiple factors behind early diversification of skull morphology in the continental radiation of New World monkeys.

Understanding the origin of diversity is a fundamental problem in evolutionary biology. The null expectation for the evolutionary diversification is that all changes in biological diversity are the result of random processes. Adaptive radiations depart from this expectation as ecological factors and natural selection are supposed to play a central role in driving exceptional diversification. However, it is not well understood how large-scale continental radiations, given their characteristics, fit to these opposing theoretical models. Here, we used phylogenetic comparative methods and geometric morphometrics to study the evolutionary process of cranial diversification in the continental radiation of New World monkeys. Particularly, we tested several alternative evolutionary scenarios for morphological evolution in the clade. Results indicated that despite the platyrrhine radiation being old and geographically widespread, the formative patterns arising from the initial stages of diversification probably associated with an adaptive radiation can still be recognized today. We also show that no single explored factor (e.g., ecological or allometric) can be invoked as a complete explanation for the observed phenotypic diversity patterns in the clade and, moreover, that different cranial regions exhibit particular macroevolutionary patterns. Together, our results highlight the evident complexity behind large-scale evolutionary radiations.

Articular scaling and body mass estimation in platyrrhines and catarrhines: Modern variation and application to fossil anthropoids.

Body mass is an important component of any paleobiological reconstruction. Reliable skeletal dimensions for making estimates are desirable but extant primate reference samples with known body masses are rare. We estimated body mass in a sample of extinct platyrrhines and Fayum anthropoids based on four measurements of the articular surfaces of the humerus and femur. Estimates were based on a large extant reference sample of wild-collected individuals with associated body masses, including previously published and new data from extant platyrrhines, cercopithecoids, and hominoids. In general, scaling of joint dimensions is positively allometric relative to expectations of geometric isometry, but negatively allometric relative to expectations of maintaining equivalent joint surface areas. Body mass prediction equations based on articular breadths are reasonably precise, with %SEEs of 17-25%. The breadth of the distal femoral articulation yields the most reliable estimates of body mass because it scales similarly in all major anthropoid taxa. Other joints scale differently in different taxa; therefore, locomotor style and phylogenetic affinity must be considered when calculating body mass estimates from the proximal femur, proximal humerus, and distal humerus. The body mass prediction equations were applied to 36 Old World and New World fossil anthropoid specimens representing 11 taxa, plus two Haitian specimens of uncertain taxonomic affinity. Among the extinct platyrrhines studied, only Cebupithecia is similar to large, extant platyrrhines in having large humeral (especially distal) joints. Our body mass estimates differ from each other and from published estimates based on teeth in ways that reflect known differences in relative sizes of the joints and teeth. We prefer body mass estimators that are biomechanically linked to weight-bearing, and especially those that are relatively insensitive to differences in locomotor style and phylogenetic history. Whenever possible, extant reference samples should be chosen to match target fossils in joint proportionality.

Early evolutionary diversification of mandible morphology in the New World monkeys (Primate, Platyrrhini).

New World monkeys (order Primates) are an example of a major mammalian evolutionary radiation in the Americas, with a contentious fossil record. There is evidence of an early platyrrhine occupation of this continent by the Eocene-Oligocene transition, evolving in isolation from the Old World primates from then on, and developing extensive morphological and size variation. Previous studies postulated that the platyrrhine clade arose as a local version of the Simpsonian ecospace model, with an early phase involving a rapid increase in morphological and ecological diversity driven by selection and ecological opportunity, followed by a diversification rate that slowed due to niche-filling. Under this model, variation in extant platyrrhines, in particular anatomical complexes, may resemble patterns seen among middle-late Miocene (10-14 Ma) platyrrhines as a result of evolutionary stasis. Here we examine the mandible in this regard, which may be informative about the dietary and phylogenetic history of the New World monkeys. Specifically, we test the hypothesis that the Simpsonian ecospace model applies to the platyrrhine mandible through a geometric morphometric analysis of digital images of the jaws of extant and extinct species, and we compare these results to those obtained using a phylogenetic comparative approach based on extant species. The results show a marked phylogenetic structure in the mandibular morphology of platyrrhines. Principal component analyses highlight the morphological diversity among modern forms, and reveal a similar range of variation for the clade when fossil specimens are included. Disparity-Through-Time analysis shows that most of the shape variation between platyrrhines originated early in their evolution (between 20 and 15 Ma). Our results converge with previous studies of body mass, cranial shape, the brain and the basicranium to show that platyrrhine evolution might have been shaped by an early increase in morphological variation followed by a decelerated rate of diversification and evolutionary stasis.

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.

New primate locality from the early Miocene of Patagonia, Argentina.

OBJECTIVES: The purpose of this work is to present a new primate locality with evidence that increases the knowledge on the radiation of the extinct platyrrhine primates. MATERIALS AND METHODS: We studied the new specimen and compared it to specimens identified as Mazzonicebus almendrae. RESULTS: The new first and second molars were comparable to Mazzonicebus almendrae in all morphological details, allowing us to allocate the new specimen to M. almendrae and add comments on morphological variation in this species regarding the orientation of the labial cristae and development of the anterolingual cingulum. This new maxilla also present the first known M3 for the species. DISCUSSION: The new specimen increases our knowledge of the extinct platyrrhines from Patagonia. Their age and geographical distribution ranges from early to middle Miocene in an area between 40° to 47° of southern latitude.

Structural Diversity of the Extensor Digitorum Profundus Muscle Complex in Platyrrhini.

Separate extension of fingers in the hand of primates is performed by 3 muscles: m. extensor pollicis longus, m. extensor digiti secundi, and m. extensor digitorum lateralis. Here it is proposed to consider them as parts of the extensor digitorum profundus muscular complex. The diversity in structure of these muscles in primates is examined based both on original anatomical study of New World monkeys and analysis of extensive published data on primates from different taxonomic groups. It is shown that in these muscles there are 2 main types of structure variations - the division of the muscle belly into several heads which give rise to separate tendons, and the split of the single terminal tendon into several branches. The first type of modification ensures the possibility of a separate management of the fingers, and the second, on the contrary, ensures the coupled control of extension of fingers. A scheme of evolutionary transformations of muscles belonging to the complex of the deep extensors of fingers is proposed.