Thun'da, King of the Congo #1

Pilot Roger Drum crash lands in a lost prehistoric valley in Africa with no way of getting out. He helps a tribe of cave dwellers, especially Pha, one of the female membrs, against a tribe of more violent primitive men. When he defeats a gigantic serpent they welcome him into the tribe, calling him Thun’da, for the sound Drum made as he fired his last bullets into the serpent.