The two heads are separated by a triangular surface depression, the lesser supraclavicular fossa.
These additional heads made the SCM muscle thick and bulky to an extent that caused extreme reduction in the size of the lesser supraclavicular fossa.
Since the SCM is used as a myocutaneous flap in various graft surgeries (8,9) and the lesser supraclavicular fossa is utilized for central venous access (10), these variations must be kept in mind while approaching the region to avoid complications.
The two heads of origin are separated by a triangular interval, which corresponds to a surface depression, the lesser supraclavicular fossa.
The two clavicular heads of origin of sternocleidomastoid muscle were separated by a wider triangular interval (compared to the interval between the sternal head and normal clavicular head), which corresponds to one more surface depression, the additional lesser supraclavicular fossa.