Comparative gross anatomical studies on the shoulder girdle of crested serpent eagle (Spilornis cheela) and brown wood owl (Strix leptogrammica)

The shoulder girdle gives strength and range of motion to the wings of birds and plays a functional role in flight mechanism of birds. The present study was designed to compare the morphological features of shoulder girdle bones in crested serpent eagle and brown wood owl. The shoulder girdle comprised of the scapula, coracoid and fused clavicle i.e. furculum in both species. The proximal extremities of bones of shoulder girdle formed a foramen triosseum in both the species for tendon of supracoracoideus muscle. The proximal end of the scapula of crested serpent eagle presents a pneumatic foramen which was absent in the brown wood owl. The coracoid of crested serpent eagle presents a large pneumatic foramen at the medial surface of the acrocoracoid process. A piercing type of foramen was characteristic in the coracoid of both species. Procoracoid process was triangular in shape with a broad base in both the species with pointed apex in brown wood owl and short apex in crested serpent eagle. The clavicle was thin, slender and highly curved in crested serpent eagle, whereas it was slender and rod-like in brown wood owl. Numerous pneumatic foramina were present in the proximal extremity of the clavicle of the crested serpent eagle, which were few in brown wood owl. The distal extremity of both clavicle fused to form a hypocleideum in crested serpent eagle, which was absent in brown wood owl.