How eggs got their shapes Adaptations for flight may have driven egg-shape variety in birds Date: June 22, 2017 Source: Harvard John A. Paulson School of Engineering and Applied Sciences ...

image: The amniotic egg, showing the semipermeable shell and the extraembryonic membranes. view more . Credit: Mike Benton. ... as in modern amphibians such as frogs and salamanders.

They had to live in or near water to feed and breed, as in modern amphibians such as frogs and salamanders. ... But the amniotic egg was the key.