Comparative myology of the pectoral and pelvic appendages of the North American porcupine (Erethizon dorsatum) and the prehensile-tailed porcupine (Coendou prehensilis). Bulletin of the AMNH ; v. 173, article 4

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[New York] : American Museum of Natural History
"The myology of the pectoral and pelvic appendages of Erethizon dorsatum, the North American porcupine, and Coendou prehensilis, the prehensile-tailed porcupine, were compared by dissection. The data were used to hypothesize on the evolutionary relationship of these two species, and the arboreal adaptations within their musculature were identified. Arboreal adaptations were observed most frequently in the forelimb. Several muscles may be important in caudal rotation of the scapula, a monement that is probably used as an aid to limb protraction during reaching movements. The cranial fibers of M. acromiotrapezius and the caudal fibers of the M. levator scapulae and M. serratus anterior complex probably function in caudal scapular rotation, but it is possible that the latter would be important in suspension of the thorax by the pectoral girdle during climbing. The cranial fibers of the M. levator scapulae and M. serratus anterior complex along with M. occipitoscapularis, M. rhomboideus anterior, and M. atlantoscapularis posterior would be used in cranial scapular rotation (the glenoid moves caudoventrally). This motion is probably used as an aid to limb retraction during climbing. M. latissimus dorsi and M. teres major have configurations which also reflect the need for powerful limb retraction in erethizontids. Several muscles, particularly M. pectoralis major and M. clavodeltoideus, are responsible for limb adduction in order to maximize the frictional forces generated between the manus and the arboreal substrate. the configuration of M. biceps brachii indicates that it is a powerful elbow flexor and an important supinator of the antebrachium. M. supinator is probably most important in maintaining the integroty of the humeroradial joint. Arboreal adaptations in the pelvic appendage were primarily concerned with positioning the pes or improving its grasping capabilities. M. tibialis anterior and M. tibialis posterior are important for inversion of the pes toward the medially lying arboreal substrate. M. plantaris brevis and M. adductor ossis sesamoideus medialis would probably depress the preaxial pad, allowing the pes to 'grasp' branches or conform to the curved substrate. The musculature of the pectoral appendages of Erethizon and Coendou was found to be similar, although some minor interspecific differences were observed. However, major interspecific differences were observed in the pelvic appendages of these animals. M. caudofemoralis and M. adductor digiti secundi are present in Erethizon but absent in Coendou. The configuration of M. flexor digitorum tibialis and M. abductor hallucis brevis in Coendou are clearly derived from the more primitive conditions as represented by Erethizon. The myological data obtained in this study, along with other morphological and paleontological data from Frazer (1978), suggest that Erethizon and Coendou were derived from a common ancestor"--P. 339.
p. 338-421 : ill. ; 26 cm.
Includes bibliographical references (p. [419]-421).