Question

Wishbone of birds is formed by
A) Pelvic girdle
B) Pectoral girdle or clavicles
C) Skull
D) Femurs

Answer 1

Hint: Wishbone is a special type of bone found near the shoulder of birds. They are articulated to each of the bird's scapulae and stay in conjunction with the coracoids and scapulae.

Complete answer:
The wishbone, also known as Furcula, is a forked bone formed by the fusion of two clavicles and is found in birds, and some dinosaur species. Its function is to strengthen the thoracic skeleton to withstand the rigors of flight. It is found as a strut between the shoulder and articulates the scapula. The structure known as the triosseal canal is formed by the wishbone in conjunction with the coracoid and the scapula and it contains the supracoracoideus muscle. This system helps in lifting the wings during the recovery stroke.

Additional Information:
The skeleton of the bird is very light due to the presence of air cavities but is very strong. The skull has a larger cranium than reptiles with a fusion of elements which suggests that birds have a fixed adult size. They can move both upper and lower jaws. They possess 39 to 3 vertebrae with remarkable variations numbering from 11 to 25 within the neck. There is a pair of complete ribs articulating with the vertebra and the ventral sternal rub that articulates further the breastbone. The pectoral girdle consists of the wishbone and the paired coracoids and scapulae. The pelvic girdle consists of the ilia, ischia, and pubes fused into a single piece with synsacrum.

So, the correct answer is option ‘B’ i.e, “Pectoral girdle or Clavicle”.

Note: At the current time, only birds possess the wishbone but several groups of theropod dinosaurs have also been found with the wishbone. Some of them are dromaeosaurids, tyrannosaurus, oviraptoridae, etc. The furcula or wishbone is considered a transformation of interclavicle rather than a fused clavicle due to its occurrence in diplodocid dinosaurs of interclavicular, Tschopp, and Mateus.