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SLING FOR THE SCAPULA

     Once the pectoral girdle was separated from the skull in tetrapods, muscles became more important in securing the scapula which no longer had any bony attachment to the axial skeleton.  In tetrapods, anterior extensions of the external oblique produces serratus anterior, levator scapulae, and rhomboid muscles which provide a sling for the scapula (Romer, p. 287).

ALLIGATOR

SLING FOR THE SCAPULA

CHICKENSLING FOR THE SCAPULA

OPOSSUM

SLING FOR THE SCAPULA

CAT

SLING FOR THE SCAPULA

SLING FOR THE SCAPULA

GOAT

SLING FOR THE SCAPULA

SHEEP

SLING FOR THE SCAPULA

COW

SLING FOR THE SCAPULA

MONKEY

SLING FOR THE SCAPULA

SERRATUS

During development, the levator scapulae (atlantoscapulares) and serratus anterior form from a continuous muscular sheet which later separates.  The levator claviculae, which exists in many monkeys and apes, is occasionally found in humans (Hartman, 1933).

OPOSSUM

SERRATUS

CAT

SERRATUS

GOAT

SERRATUS

SHEEP

SERRATUS

PIG

SERRATUS

RHESUS MONKEY

SERRATUS

HUMAN MODEL

SERRATUS