Amphisbaenians, also known as two-headed worms, resemble snakes externally; however, they are more closely related to lizards in terms of their origin. Their skin and subcutaneous muscles are connected to the underlying tissues in such a way that a skin-muscle sac is formed, similar to what is observed in earthworms, and also segmented like them, with transverse rings.
The amphisbaenian can move both forward and backward by contracting and relaxing the muscles in these segments.
