S: (n) underpart (underpart%1:05:00::) (a part lying on the lower side or underneath an animal's body) "the warbler has a white throat and underparts"; "a woodland mouse with white underparts"
S: (n) dorsum (dorsum%1:08:00::) (the back of the body of a vertebrate or any analogous surface (as the upper or outer surface of an organ or appendage or part)) "the dorsum of the foot"
S: (n) rudiment (rudiment%1:08:00::) (the remains of a body part that was functional at an earlier stage of life) "Meckel's diverticulum is the rudiment of the embryonic yolk sac"