Estudo anatômico comparativo do membro pélvico – músculos da região anterior da coxa do primata sapajus sp (macaco-prego) associado ao uso de ferramentas e bipedalismo

Abstract

The order Primates is an important mammalian radiation with a rich diversity of morphological, behavioral and ecological adaptations. The anthropoids, which the group of primates in the study are part of, are the most diffused primates with the greatest morphological diversity. The neotropical primates capuchin monkeys (Sapajus sp) and marmosets (Callithrix sp) due to their morphological, behavioral, physiological, and phylogenetic characteristics similar to chimpanzees are good models for scientific research. However, anatomical and functional data on their anterior thigh muscles are scarce or non- existent. The study of these primates, in evolutionary terms, may contribute to areas related to taxonomy and the understanding of the evolution of bipedalism. The objective of this work was to study the anatomy of the muscles of the anterior region of the thigh by the dissection of the neotropical primates Sapajus and Callithrix, and of the literature for Macaca cyclopes, Macaca fascicularis, Papio, Hylobates, Pongo, Gorilla, Pan and Homo for comparative purposes in terms of anatomical and functional aspects related to locomotor behavior. Ten adult specimens of Sapajus sp and three of Callithrix sp were dissected. Thigh dissection was performed with emphasis on the quadriceps femoris. For statistical purposes, the non- parametric comparative method was used to associate different species with the anatomical concepts of normality and variation. Allometric data were collected for the assessment of muscle strength. The quadriceps femoris of Sapajus and Callithrix in terms of anatomical parameters were identical. The rectus femoris presented only one head of origin in Macaca fascicularis, Hylobates and Pongo. According to the Law of Cosines, a head of origin for that muscle generates greater muscle force. Already the two heads of origin a better stability of the hip joint. The tensor fascia lata was the muscle with the greatest divergence among the primates in the study. Considering the set of anterior thigh muscles, Pongo showed greater divergence compared to Sapajus, which can be explained by a particular specialization of this primate in the evolution of its locomotion. Anatomically, the greatest similarity between the muscles of the anterior region of the thigh of Sapajus was with those of Callithrix, possibly because both are neotropical primates and share a closer ancestor compared to the other primates investigated and because they are quadrupeds. Modern humans had the greatest quadriceps strength, followed by Sapajus and Callithrix, demonstrating an important relationship between proportional strength of this muscle and the bipedal and quadrupedal behavior of those primates. Among the apes, Hylobates was the one that showed greater

quadriceps strength compared to Pan, Gorilla and Pongo. The area/volume model proved to be the most suitable for the assessment of muscle strength, which corroborated the Law of Cosines and the Free-Body Theory. More anatomical studies with primates, addressing the hindlimb and its muscle strength are necessary, since the absence of these data was one of the limiting factors of this study and, if they were present, they could provide a better understanding of the locomotor behavior of primates.