Since Mivart (1865), Cacajao, Chiropotes, and Pithecia have been grouped into a single taxon, which he called the subfamily Pitheciinae but which I, following Rosenberger (this issue), refer to as the living members of the tribe Pitheciini. While few today doubt the association of these three living genera, not all would place them together with Aotus and Callicebus in the subfamily Pitheciinae. This is an attempt to sort out the behavioral and morphological features of feeding and dental morphology in these taxa. Extant members of the tribe Pitheciini are adapted for sclerocarpic foraging, morphological evidence for which is found in the fossils of Soriacebus and Cebupithecia. Sclerocarpic foraging in living pitheciins is a two-stage process of seed predation involving 1) specialized features of the anterior dentition that allow removal of a hard pericarp that protects a seed or seeds, followed by 2) mastication by the posterior dentition having low cusp relief to triturate nutritious seeds of a relatively soft and uniformly pliable consistency. The dentitions of fossil pitheciins, Soriacebus and Cebupithecia, demonstrate that the hypertrophy of lower incisors plus the robustness and flaring of the canine precede development of low cusp relief on molars and premolars in the evolution of morphological features associated with sclerocarpic foraging. Features of sclerocarpic foraging are found less uniformly in the other two pitheciines, Callicebus and Aotus.

The marmosets and tamarins fill a unique ecological role among the anthropoid primates, one that has not been fully recognized. Many misconceptions--that they are primitive, monogamous, territorial, and squirrellike--pervade the literature. These misconceptions are largely the result of misinterpreting laboratory studies which have not been confirmed with identified animals in natural habitats. Recent field studies, reviewed here, indicate that marmosets and tamarins have a highly derived ecological role, are not monogamous, feed largely on insects and plant exudates, and have uniquely specialized positional behavior involving clinging to vertical tree trunks in order to feed on exudates. Accompanying these behavioral traits are a number clawlike nails on all digits except the hallux, and a three-cusped upper molar morphology. These form a suite of characteristics unique among the living primates, many of which are related to their ecological role. We believe that the marmosets and tamarins are members of a guild of exudate feeders in which plant exudates are an important component of the diet. It is within this framework of a primate foraging guild that we can best understand many of their morphological and behavioral adaptations.

Fruit color and size are significant determinants of food choice in mammals and birds, but hardness, an important physical property of fruit and seeds, has generally been overlooked as a determinant of food choice in studies of mammalian foraging behavior. Two methods were used to determine fruit hardness during a field study of two sympatric primates, the black spider monkey (Ateles paniscus) and the bearded saki monkey (Chiropotes satanas) in Surinam. We measured both puncture resistance of fruit pericarp and crushing resistance of seeds. Puncture resistance of the pericarp of some fruit opened by Chiropotes was as much as 15 times greater than that of all fruit successfully opened by Ateles. In contrast, crushing resistance of species of seeds masticated by Chiropotes was significantly lower than that of seeds swallowed by Ateles. These data demonstrate that hardness of both fruit pericarp and seed may play a significant role in food choice among sympatric vertebrates. Measurements of both puncture resistance of the pericarp and crushing resistance of the seed are necessary for understanding the significance of fruit hardness in these primates.

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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.

We suggest four ways in which human gross anatomy instructors can reinforce respect and compassion in students. First, encourage respectful language in the laboratory. The term “donor” should be used instead of “cadaver” or “corpse” in referring to the donated body because this promotes appreciation for the students' first “patient.” Second, provide the students with the actual name, age, history, and likely cause of death of the donor so that they more fully appreciate the donor as having once been a living human being. Third, prompt students to explore feelings and discuss topics stimulated by the intense experience of human dissection. Suggested topics include the students' feelings about dissecting a human being, the difficulty in deciding to donate one's body, the central importance of anatomy to a medical practitioner's role, and the historical development of the study of anatomy. Fourth, hold a memorial ceremony, in which both students and faculty participate, as a positive closure to an emotionally and intellectually intense course. Additionally, a ceremony reinforces salutary values in students, enhances social bonding among students, and encourages their appreciation of various cultural and religious beliefs. These methods introduce a new dimension of experience for anatomy students. We have developed these methods in response to what we view as a negative trend in the medical profession in which health care becomes technical and patients become objects. It is our role as faculty to reinforce respectful and compassionate attitudes in medical students from the very beginning. © 1995 WiIey‐Liss, Inc.

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