Rectilinear locomotion

This mode of locomotion is most often associated with snakes, particularly heavy-bodied species like terrestrial pythons and boas, though most snakes are capable of it. Unlike all other modes of snake locomotion, which rely upon bending the body, in this form the body is not flexed for any purpose except turning.

This method of locomotion relies on two opposing muscles, the costcutaneous inferior and superior, which are present on every rib, connecting the rib to the skin. The ribs themselves do not move, only the skin. First, a secton of belly is lifted from the ground and placed ahead of it's former position by the costcutaneous superior, then the costcutaneous inferior pulls backwards while the belly scales are on the ground, propelling the snake forwards. These sections of contact propagate posteriorly, resulting in continuous motion.

This method of locomotion is inefficient and slow, but also almost noiseless and very hard to detect, making it the mode of choice for many species when stalking prey.