No joint exists between each scapula and the thoracic cage, instead the muscular connection between the two permits relatively great mobility of the shoulder girdle in relation to the pelvic girdle.

• 大多数哺乳动物的锁骨也退化了。人类的锁骨还通过关节与胸骨相连。除灵长目动物外大多数哺乳动物的前肢仅通过肩胛骨与躯干相连。在肩胛骨与胸骨间有强有力的肌肉。