Cephalopagus twins are a rare type of conjoined twins. They are fused from the vertex to the umbilicus. They share a common cranium with either one composite face or two faces on opposite sides of the conjoined head.
The thoraces are fused with fusion of liver, heart and the upper gastrointestinal system upto the division at the Meckel diverticulum. There are usually four arms and legs. These twins tend to be non viable.