We report a large kindred in which individuals presented with fixation of the scapula to the first rib by a congenitally short costocoracoid ligament. Cosmetic deformity with rounding of the shoulder and loss of the anterior clavicular contour was the main concern of the affected individuals. Movements requiring rotation or retraction of the scapula were limited, although this did not interfere with normal activities. Surgical treatment consists of excision of the costocoracoid ligament and resulted in some correction of the cosmetic deformity. The pedigree supports an autosomal dominant mode of inheritance with variable expression. The abnormality results in a pectoral girdle which is reminiscent of that seen in the monotremes.