Rhomboideus Occipitalis
Shoulder & Arm
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Rhomboideus occipitalis is basically a ‘bonus rhomboid’ that most people do not have. It is also called rhomboideus capitis or occipitoscapularis, because it can run from the occipital bone of the skull to the scapula.
Function
Likely assists scapular retraction, slight elevation, and stabilization of the medial scapular border. Because it links the occiput to the scapula it may weakly influence head/neck positioning when the scapula is fixed, but its exact function in humans is not fully proven.
Origin
Superior nuchal line / occipital bone, often deep to or near the trapezius attachment.
Insertion
Medial border of the scapula near the base/level of the scapular spine; some descriptions place it between rhomboideus minor and levator scapulae, with possible slips to serratus posterior superior fascia.
Innervation
Not definitively confirmed. One human case could not identify the nerve supply. Best labelled probable dorsal scapular nerve by rhomboid-group association, but unconfirmed.