Which one of the following in birds, indicates their reptilian...

Reptiles too are egg-laying organisms. But in aves, the eggs have a calcareous shell around them. In aves, the heart is four-chambered, while in reptiles the heart is 3 chambered and is incompletely divided to form a four-chambered heart. They have two special chambers called crop and gizzard in their digestive tract. Gizzard is modified for grinding food and crop for storing food on a temporary basis.