Question

Besides pneumatic bones, another useful flight adaptation in birds is
a. Syrinx
b. Pygostyle
c. Furcula
d. Quill feathers

Answer 1

Hint: These are bones that are occupied by air spaces as opposed to bone marrow. As far as I know, birds are the only animals with pneumatic bones. Air sacs, the blind-ended expansion of the bronchial tree of the respiratory system, extend their diverticula into the medullary cavity of bones, and these bones are termed as pneumatic bones.

Complete answer:
> Quill feathers are present at the base of quill wings. These are called coverts. These are small feathers found in birds. It is meant for filling gaps on the wings and tail. They are generally small and their main function is that they oppose the buoyancy of the air. So, option D) quill feathers are correct.

> Syrinx is present at the base of the trachea. It is present in birds, as air passes through the syrinx it's able to expand and contract to allow the bird a much wider range of sound. So option A is incorrect.

> Pygostyle: It is the bone present in the posterior end of the birds. It is formed by the fusion of several caudal vertebrates. So option B) Pygostyle is incorrect.

> Furcula: The furcula is also connected to limb muscles and lung muscle. The furcula, gastralia, and pubis all make a single muscular structure acting like a corset for theropods to aid breathing. So options – Furcula is incorrect.

Hence, the correct answer is option (D).

Note: Air sacs, the blind-ended expansion of the bronchial tree of the respiratory system, extend their diverticula into the medullary cavity of bones, and these bones are termed as pneumatic bones. The presence of air sacs makes these bones lighter in weight and thus serves as an adaptation giving the flying ability for the birds.