Which one of the following in birds indicates their reptilian ancesty?

Options

A. Scales on their hindimbs
B. Four chambered heart
C. Two special chambers crop and gizzard in their digestive tract
D. Eggs with a calcareous shell

Answer

D

Explanation

Nearly a century ago TH Huxley called birds glorified reptiles' thereby meaning that birds have evolved from some reptilian ancestor. Both birds and reptiles lay the same type of eggs, which are deposited outside water. Eggs are large and telolecithal. The ovum is surrounded by albumen, an egg membrane and a thick hard calcareous shell, which are all secreted by special glands located in the walls of oviduct.
Like mammals birds also have complete four chambered heart with double circulation, in which there is no mixing of pure and impure bloods.
Whereas, the ventricle is imperfectly divided in reptiles, resulting in partial mixing of blood.