Why do we keep both snake and turtle in the same class?

Both snake and turtle have been placed by taxonomists in class Reptilia of phylum Chordata. This is done because of following features; (i) skin without glands; (ii) three-chambered (in-fact incompletely four chambered) heart; (iii) respiration through lungs; (iv) cold blooded; (v) hard shelled eggs; (vi) embryo protected by extra embryonic membranes.