The present study describes the flexor and extensor muscles in Cebus libidinosus' forearm and compares them with those from humans, chimpanzees and baboons. The data is presented in quantitative anatomical indices for similarity. The capuchin forearm muscles showed important similarities with chimpanzees and humans, particularly those that act on thumb motion and allow certain degree of independence from other hand structures, even though their configuration does not enable a true opposable thumb. The characteristics of Cebus' forearm muscles corroborate the evolutionary convergence towards an adaptive behavior (tool use) between Cebus genus and apes.
Capuchin monkeys present a wide variety of manipulatory skills and make routine use of tools both in captivity and in the wild. Efficient handling of objects in this genus has led several investigators to assume near-human thumb movements despite the lack of anatomical studies. Here we perform an anatomical analysis of muscles and bones in the capuchin hand. Trapezo-metacarpal joint surfaces observed in capuchins indicate that medial rotation of metacarpal I is either absent or very limited. Overall, bone structural arrangement and thumb position relative to the other digits and the hand’s palm suggest that capuchins are unable to perform any kind of thumb opponency, but rather a ‘lateral pinch’ movement. Although the capuchin hand apparatus bears other features necessary for complex tool use, the lack thumb opposition movements suggests that a developed cognitive and motor nervous system may be even more important for high manipulatory skills than traditionally held.
RESUMO.-[Anatomia comparativa dos nervos da coxa de Cebus libidinosus (Rylands et al., 2000).]Primatas não-humanos têm constituído um importante grupo entre os animais submetidos a vários estudos. Estudos etológi-cos, evolutivos e paleontológicos revelaram alterações das estruturas anatômicas ligada à evolução dos primatas, considerado em estudos sobre a anatomia comparativa entre Cebus libidinosus e outros primatas neotropicais ou provenientes do Velho Mundo, e as modalidades de conhecimento sobre sua anatomia pode representar um fator importante para a sua preservação e proteção quando os animais são levados às clínicas veterinárias após acidentes ou doenças. Em termos de importância veterinária, ás vezes esses animais chegam na clínica médica veteriná-ria após acidentes, necessitando de cirurgia ou tratamento clínico, mas os poucos dados disponíveis sobre a anatomia tem dificultado o procedimento correto. A principal justificativa para os estudos sobre C. libidinosus é devido a pouca informação sobre sua anatomia na literatura cientí- Non-human primates have constituted an important group among animals subjected to various studies. Ethological, evolutionary and paleontological studies have revealed changes in anatomical structures linked to the evolution of primates, considered in studies on the comparative anatomy between Cebus libidinosus and other neotropical monkeys or those from the Old World, and the detailed knowledge on their anatomy may represent an important factor for their preservation and protection when the animals are brought to veterinary clinics after accidents or illnesses. In terms of veterinary importance, sometimes these animals arrive in the veterinary medical clinics after accidents, needing surgery or clinical treatment, but the little data available on anatomy has impaired the correct proceedings. The main justification for studies on C. libidinosus, is due to little information about the anatomy related to C. libidinosus in Brazilian and worldwide scientific literature. In this study, the distribution, enervation and path of the femoral and sciatic nerves of the pelvic limb (thigh) of C. libidinosus were studied and these results were compared with literature on the anatomy of humans, chimpanzees and baboons. In general, the enervation model of the four primates is identical, but in specific terms, the differences in enervations indicate evolution convergence closer to the branch of baboons in the evolutionary tree, and these data corroborate other comparative studies in relation to the same primates to vessels, muscles and nerves. In conclusion, the nerve organization in the thigh of C. libidinosus is identical to baboon, chimpanzee and homo, but more similar to baboon. The specific differences found indicate an ancient phylogenic origin to C. libidinosus and baboons (data corroborated by other studies). Roqueline A.G.M.F. fica no Brasil e no mundo. Neste trabalho, a distribuição, inervação e os trajetos dos nervos femoral e isquiático do membro pélvico (coxa) de C. libidinosus for...
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