Which is NOT one of the general features that make birds and reptiles similar?

A)Both birds and nonavian reptiles have a single middle ear bone
B)The skulls articulate with the first neck vertebra by a single occipital condyle
C)Both have a lower jaw composed of five or six bones
D)Both birds and reptiles lay eggs and the early embryo develops on the surface by shallow cleavage divisions
E)All of the choices are similarities that distinguish birds and reptiles from mammals