The adaptive radiation of modern New World monkeys unfolded as the major lineages diversified within different dietary-adaptive zones predicated upon a fundamentally frugivorous habit. The broad outlines of this pattern can be seen in the fossil record, beginning in the early Miocene. Cebids are obligate frugivorous predators. The smallest forms (Cebuella, Callithrix) are specialized exudativores, and the largest (cebines) are seasonally flexible omnivores, feeding particularly on insects (Saimiri) or "hard" foods, such as pith and palm nuts (Cebus), when resources are scarce. The smaller-bodied atelids (Callicebus, Aotus) may use insects or leaves opportunistically, but pitheciins (saki-uakaris) specialize on seeds as their major protein source. The larger atelines (Alouatta, Brachyteles) depend on leaves or on ripe fruit (Ateles). Locomotion, body size, and dietary adaptations are linked: claws and small body size opened the canopy-subcanopy niche to callitrichines; climbing and hanging, the fine-branch setting to the atelines; large size and strength, semiprehensile tails, and grasping thumbs, the extractive insectivory of Cebus; deliberate quadrupedalism, the energy-saving transport of folivorous Alouatta. Body size increases and decreases occurred often and in parallel within guilds and lineages. Conventional dietary categories, particularly frugivory, are inadequate for organizing the behavioral and anatomical evidence pertinent to evolutionary adaptation. Related models of morphological evolution based on feeding frequencies tend to obfuscate the selective importance of "critical functions," responses to the biomechanically challenging components of diet that may be determined by a numerically small, or seasonal, dietary fraction. For fossils, body size is an unreliable indicator of diet in the absence of detailed morphological information. More attention needs to be given to developing techniques for identifying and quantifying mechanically significant aspects of dental form, the physical properties of primate foods, their mode of access, and the cycles of availability and nutritional value.

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Mechanico-functional features of molar form were studied in Callithrix, Alouatta, Pithecia and Cebus. Molars of Callithrix and Alouatta are adapted to loading foods under relatively high occlusal pressure; those of Pithecia and Cebus, under relatively low occlusal pressure. General functional considerations suggest that these taxa are adapted to insectivorous, folivorous, frugivorous and omnivorous diets, respectively. The physical properties of foods, principally mechanical strength and deformability, determine the selective pressures involved in the evolutionary adaptation of molar form. A dietary classification based upon percentages of foods eaten does not always reflect morphological adaptations. Homologous parts of teeth and homologous parts of the masticatory cycle do not always subserve equivalent functions. The relevance of functional occlusal analysis for deciphering phylogeny and explaining evolutionary grades is stressed.

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We contrast our approach to a phylogenetic diagnosis of the order Primates, and its various supraspecific taxa, with definitional procedures. The order, which we divide into the semiorders Paromomyiformes and Euprimates, is clearly diagnosable on the basis of well-corroborated information from the fossil record. Lists of derived features which we hypothesize to have been fixed in the first representative species of the Primates, Euprimates, Strepsirhini, Haplorhini, and Anthropoidea, are presented. Our classification of the order includes both holophyletic and paraphyletic groups, depending on the nature of the available evidence.We discuss in detail the problematic evidence of the basicranium in Paleogene primates and present new evidence for the resolution of previously controversial interpretations. We renew and expand our emphasis on postcranial analysis of fossil and living primates to show the importance of understanding their evolutionary morphology and subsequent to this their use for understanding taxon phylogeny. We reject the much advocated %ladograms first, phylogeny next, and scenario third" approach which maintains that biologically founded character analysis, i.e., functional-adaptive analysis and paleontology, is irrelevant to genealogy hypotheses. Unlike the cladistic rules of operations demand, we advocate and use a priori weighting of characters.We discuss the evidence for the various proposed relationships of the earliest euprimates, the Adapidae and Omomyidae, and show that linking the former with living Strepsirhini and the latter with living Haplorhini does not depend on the assumption of the presence of soft-anatomical characters in the fossils. On the contrary, it is the sharing of derived hard anatomical features of the fossil taxa with the living groups which makes their possession of either strepsirhine or haplorhine "soft" attributes probable.We discuss the relative merits of the use of the grade concept (with its widely recognized implication of polyphyly) in attempts to group primates and maintain that there exists no evidence for either an "archaic primate" or a prosimian or an anthropoid grade. All the characters in the literature attributed to these are inherited from the first representatives of either the semiorder Paromomyiformes or the semiorder Euprimates or the semisuborder Anthropoidea. Consequently, we find neither descriptive nor didactic merit in gradal arrangements, the goals of which can be much better served by a phylogenetic (not cladistic) classification.

Please cite this article as: Aristide, L., Rosenberger, A.L., Tejedor, M., Ivan Perez, S., Modeling lineage and phenotypic diversification in the New World monkey (Platyrrhini, Primates) radiation, Molecular Phylogenetics and Evolution (2013), doi: http://dx.doi.org/10. 1016/j.ympev.2013.11.008 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Adaptive radiations that have taken place in the distant past can now be more 2 thoroughly studied with the availability of large molecular phylogenies and comparative 3 data drawn from extant and fossil species. Platyrrhines are a good example of a major 4 mammalian evolutionary radiation confined to a single continent, involving a relatively 5 large temporal scale and documented by a relatively small but informative fossil record. 6 Modeling lineage and phenotypic diversification in the NewHere, we present comparative evidence using data on extant and fossil species to 7 explore alternative evolutionary models in an effort to better understand the process of 8 platyrrhine lineage and phenotypic diversification. Specifically, we compare the 9 likelihood of null models of lineage and phenotypic diversification versus various 10 models of adaptive evolution. Moreover, we statistically explore the main ecological 11 dimension behind the platyrrhine diversification. Contrary to the previous proposals, 12 our study did not find evidence of a rapid lineage accumulation in the phylogenetic tree 13 of extant platyrrhine species. However, the fossil-based diversity curve seems to show a 14 slowdown in diversification rates toward present times. This also suggests an early high 15 rate of extinction among lineages within crown Platyrrhini. Finally, our analyses support 16 the hypothesis that the platyrrhine phenotypic diversification appears to be characterized 17 by an early and profound differentiation in body size related to a multidimensional 18 niche model, followed by little subsequent change (i.e., stasis). 19