Why Atlas and Axis are called deviant vertebra?

Why Atlas and Axis are called deviant vertebra?
The vertebra which contains body,archand processes is called a typical vertebra.It has 3 processes.
                                        1.Spinous process
                                        2.Articular process
                                        3.Transverse process

Articular processes are 2 not far away and wide off from each cranial and caudal aspects.
In atlas,the body and spinous process are absent.Theres a fovea dentis which is absent in typical vertebra.Again in axis,the cranial articular orocesses are absent.It has a projection known as odontoid process which is absent in typical vertebra.Thats why atlas and axis are called blinking vertebra.