Functional Myology of the Neck in Primates

The neck is often used to study postural and locomotor behaviors across primates. Partially due the complexity of this 3D system, there has not yet been a quantitative comparative nuchal muscle function. In study, we applied innovative methods visualize, quantify, compare epaxial muscles among primate taxa characterize relationship between trunk posture, extreme head turning behaviors, forelimb-dominated below branch suspensory locomotion DiceCT imaging, fascicle-tracking, visualization were all attachment sites, orientations, estimates force for 19 five species that displayed contrasting behaviors. To explore orientation bellies, ternary diagrams used. Results show most forces scale with isometry, but musculature varies according positional behavior Semisuspensory have more dorsoventrally oriented cranial bellies trapezius than closely related, non-suspensory taxa. Pronograde primates powerful longissimus capitis compared orthograde Carlito, noted its pronounced transversely sternocleidomastoid in addition obliquus superior muscle. latter also seen Propithecus. These findings support hypothesis certain key are related Therefore, bony sites observed vary could aid understanding extinct