- the short head of the biceps is monoarticular, whereas it is biarticular in most primates. In gibbons, the short head originates from the lesser tubercle of the humerus, whereas it originates from the coracoid process of the scapula in humans
- only the long head of the biceps (originating from the supraglenoid) crosses the glenohumeral joint in gibbons
- we found no anconeus lateralis muscle in any of our gibbon specimens, leaving the triceps as the only elbow extensor in gibbons
- some clear variations in origin or insertion were found for brachioradialis (BR), APL, flexor digitorum profundus (FDP) and the supinator muscle (Sup)
- gibbons possess a dorso-epitrochlearis muscle that connects the latissimus dorsi to the short head of the biceps (...) In humans, this muscle is reduced to fascia
- Tendons are prominent in most muscles of the gibbon forelimb but are particularly extensive in muscles crossing the wrist joint.
- The longest tendons (relative to muscle belly length) are found in the muscles that cross the wrist muscles, in particular in the flexor and ulnar and radial deviator groups
- The shoulder muscles, especially the adductors, have the shortest tendons
- The SIL, an estimate of the stress in a tendon while the muscle is exerting maximum isometric stress, is largest for the tendons of the elbow and wrist/digital flexors